8.4: Intermolecular forces
25
Harper College Chemistry Department
As was the case for gaseous substances, the kinetic molecular theory may be used to explain the behavior of solids and liquids. In the following description, the term particle will be used to refer to an atom, molecule, or ion. Note that we will use the popular phrase “intermolecular attraction” to refer to attractive forces between the particles of a substance, regardless of whether these particles are molecules, atoms, or ions. The phrase “intermolecular forces” is also used.
Consider these two aspects of the molecular-level environments in solid, liquid, and gaseous matter:
- Particles in a solid are tightly packed together and often arranged in a regular pattern; in a liquid, they are close together with no regular arrangement; in a gas, they are far apart with no regular arrangement.
- Particles in a solid vibrate about fixed positions and do not generally move in relation to one another; in a liquid, they move past each other but remain in essentially constant contact; in a gas, they move independently of one another except when they collide.
The differences in the properties of a solid, liquid, or gas reflect the strengths of the attractive forces between the atoms, molecules, or ions that make up each phase. The phase in which a substance exists depends on the relative extents of its intermolecular forces (IMFs) and the kinetic energies (KE) of its molecules. IMFs are the various forces of attraction that may exist between the atoms and molecules of a substance due to electrostatic phenomena, as will be detailed in this module. These forces serve to hold particles close together, whereas the particles’ KE provides the energy required to overcome the attractive forces and thus increase the distance between particles. Figure 1 illustrates how changes in physical state may be induced by changing the temperature, hence, the average KE, of a given substance.
As an example of the processes depicted in this figure, consider a sample of water. When gaseous water is cooled sufficiently, the attractions between H 2 O molecules will be capable of holding them together when they come into contact with each other; the gas condenses, forming liquid H 2 O. For example, liquid water forms on the outside of a cold glass as the water vapor in the air is cooled by the cold glass, as seen in Figure 2 .
We can also liquefy many gases by compressing them, if the temperature is not too high. The increased pressure brings the molecules of a gas closer together, such that the attractions between the molecules become strong relative to their KE. Consequently, they form liquids. Butane, C 4 H 10 , is the fuel used in disposable lighters and is a gas at standard temperature and pressure. Inside the lighter’s fuel compartment, the butane is compressed to a pressure that results in its condensation to the liquid state, as shown in Figure 3 .
Finally, if the temperature of a liquid becomes sufficiently low, or the pressure on the liquid becomes sufficiently high, the molecules of the liquid no longer have enough KE to overcome the IMF between them, and a solid forms. A more thorough discussion of these and other changes of state, or phase transitions, is provided in a later module of this chapter.
Access this interactive simulation on states of matter, phase transitions, and intermolecular forces. This simulation is useful for visualizing concepts introduced throughout this chapter.
Forces between Molecules
Under appropriate conditions, the attractions between all gas molecules will cause them to form liquids or solids. This is due to intermolecular forces, not intra molecular forces. Intra molecular forces are those within the molecule that keep the molecule together, for example, the bonds between the atoms. Inter molecular forces are the attractions between molecules, which determine many of the physical properties of a substance. Figure 4 illustrates these different molecular forces. The strengths of these attractive forces vary widely, though usually the IMFs between small molecules are weak compared to the intramolecular forces that bond atoms together within a molecule. For example, to overcome the IMFs in one mole of liquid HCl and convert it into gaseous HCl requires only about 17 kilojoules. However, to break the covalent bonds between the hydrogen and chlorine atoms in one mole of HCl requires about 25 times more energy—430 kilojoules.
All of the attractive forces between neutral atoms and molecules are known as van der Waals forces, although they are usually referred to more informally as intermolecular attraction. We will consider the various types of IMFs in the next three sections of this module.
Dispersion Forces
One of the three van der Waals forces is present in all condensed phases, regardless of the nature of the atoms or molecules composing the substance. This attractive force is called the London dispersion force in honor of German-born American physicist Fritz London who, in 1928, first explained it. This force is often referred to as simply the dispersion force. Because the electrons of an atom or molecule are in constant motion (or, alternatively, the electron’s location is subject to quantum-mechanical variability), at any moment in time, an atom or molecule can develop a temporary, instantaneous dipole if its electrons are distributed asymmetrically. The presence of this dipole can, in turn, distort the electrons of a neighboring atom or molecule, producing an induced dipole. These two rapidly fluctuating, temporary dipoles thus result in a relatively weak electrostatic attraction between the species—a so-called dispersion force like that illustrated in Figure 5 .
Dispersion forces that develop between atoms in different molecules can attract the two molecules to each other. The forces are relatively weak, however, and become significant only when the molecules are very close. Larger and heavier atoms and molecules exhibit stronger dispersion forces than do smaller and lighter atoms and molecules. F 2 and Cl 2 are gases at room temperature (reflecting weaker attractive forces); Br 2 is a liquid, and I 2 is a solid (reflecting stronger attractive forces). Trends in observed melting and boiling points for the halogens clearly demonstrate this effect, as seen in Table .
| Melting and Boiling Points of the Halogens | ||||
|---|---|---|---|---|
| Halogen | Molar Mass | Atomic Radius | Melting Point | Boiling Point |
| fluorine, F 2 | 38 g/mol | 72 pm | 53 K | 85 K |
| chlorine, Cl 2 | 71 g/mol | 99 pm | 172 K | 238 K |
| bromine, Br 2 | 160 g/mol | 114 pm | 266 K | 332 K |
| iodine, I 2 | 254 g/mol | 133 pm | 387 K | 457 K |
| astatine, At 2 | 420 g/mol | 150 pm | 575 K | 610 K |
The increase in melting and boiling points with increasing atomic/molecular size may be rationalized by considering how the strength of dispersion forces is affected by the electronic structure of the atoms or molecules in the substance. In a larger atom, the valence electrons are, on average, farther from the nuclei than in a smaller atom. Thus, they are less tightly held and can more easily form the temporary dipoles that produce the attraction. The measure of how easy or difficult it is for another electrostatic charge (for example, a nearby ion or polar molecule) to distort a molecule’s charge distribution (its electron cloud) is known as polarizability. A molecule that has a charge cloud that is easily distorted is said to be very polarizable and will have large dispersion forces; one with a charge cloud that is difficult to distort is not very polarizable and will have small dispersion forces.
London Forces and Their Effects
Order the following compounds of a group 14 element and hydrogen from lowest to highest boiling point: CH 4 , SiH 4 , GeH 4 , and SnH 4 . Explain your reasoning.
Solution
Applying the skills acquired in the chapter on chemical bonding and molecular geometry, all of these compounds are predicted to be nonpolar, so they may experience only dispersion forces: the smaller the molecule, the less polarizable and the weaker the dispersion forces; the larger the molecule, the larger the dispersion forces. The molar masses of CH 4 , SiH 4 , GeH 4 , and SnH 4 are approximately 16 g/mol, 32 g/mol, 77 g/mol, and 123 g/mol, respectively. Therefore, CH 4 is expected to have the lowest boiling point and SnH 4 the highest boiling point. The ordering from lowest to highest boiling point is expected to be CH 4 < SiH 4 < GeH 4 < SnH 4 .
A graph of the actual boiling points of these compounds versus the period of the group 14 element shows this prediction to be correct:
Check Your Learning
Order the following hydrocarbons from lowest to highest boiling point: C 2 H 6 , C 3 H 8 , and C 4 H 10 .
C 2 H 6 < C 3 H 8 < C 4 H 10 . All of these compounds are nonpolar and only have London dispersion forces: the larger the molecule, the larger the dispersion forces and the higher the boiling point. The ordering from lowest to highest boiling point is therefore C 2 H 6 < C 3 H 8 < C 4 H 10 .
The shapes of molecules also affect the magnitudes of the dispersion forces between them. For example, boiling points for the isomers n -pentane, isopentane, and neopentane (shown in Figure 6 ) are 36 °C, 27 °C, and 9.5 °C, respectively. Even though these compounds are composed of molecules with the same chemical formula, C 5 H 12 , the difference in boiling points suggests that dispersion forces in the liquid phase are different, being greatest for n -pentane and least for neopentane. The elongated shape of n -pentane provides a greater surface area available for contact between molecules, resulting in correspondingly stronger dispersion forces. The more compact shape of isopentane offers a smaller surface area available for intermolecular contact and, therefore, weaker dispersion forces. Neopentane molecules are the most compact of the three, offering the least available surface area for intermolecular contact and, hence, the weakest dispersion forces. This behavior is analogous to the connections that may be formed between strips of VELCRO brand fasteners: the greater the area of the strip’s contact, the stronger the connection.
Geckos have an amazing ability to adhere to most surfaces. They can quickly run up smooth walls and across ceilings that have no toe-holds, and they do this without having suction cups or a sticky substance on their toes. And while a gecko can lift its feet easily as it walks along a surface, if you attempt to pick it up, it sticks to the surface. How are geckos (as well as spiders and some other insects) able to do this? Although this phenomenon has been investigated for hundreds of years, scientists only recently uncovered the details of the process that allows geckos’ feet to behave this way.
Geckos’ toes are covered with hundreds of thousands of tiny hairs known as setae , with each seta, in turn, branching into hundreds of tiny, flat, triangular tips called spatulae . The huge numbers of spatulae on its setae provide a gecko, shown in Figure 7 , with a large total surface area for sticking to a surface. In 2000, Kellar Autumn , who leads a multi-institutional gecko research team, found that geckos adhered equally well to both polar silicon dioxide and nonpolar gallium arsenide. This proved that geckos stick to surfaces because of dispersion forces—weak intermolecular attractions arising from temporary, synchronized charge distributions between adjacent molecules. Although dispersion forces are very weak, the total attraction over millions of spatulae is large enough to support many times the gecko’s weight.
In 2014, two scientists developed a model to explain how geckos can rapidly transition from “sticky” to “non-sticky.” Alex Greaney and Congcong Hu at Oregon State University described how geckos can achieve this by changing the angle between their spatulae and the surface. Geckos’ feet, which are normally nonsticky, become sticky when a small shear force is applied. By curling and uncurling their toes, geckos can alternate between sticking and unsticking from a surface, and thus easily move across it. Further investigations may eventually lead to the development of better adhesives and other applications.
Watch this video to learn more about Kellar Autumn’s research that determined that van der Waals forces are responsible for a gecko’s ability to cling and climb.
Dipole-Dipole Attractions
Recall from the chapter on chemical bonding and molecular geometry that polar molecules have a partial positive charge on one side and a partial negative charge on the other side of the molecule—a separation of charge called a dipole . Consider a polar molecule such as hydrogen chloride, HCl. In the HCl molecule, the more electronegative Cl atom bears the partial negative charge, whereas the less electronegative H atom bears the partial positive charge. An attractive force between HCl molecules results from the attraction between the positive end of one HCl molecule and the negative end of another. This attractive force is called a dipole-dipole attraction—the electrostatic force between the partially positive end of one polar molecule and the partially negative end of another, as illustrated in Figure 8 .
The effect of a dipole-dipole attraction is apparent when we compare the properties of HCl molecules to nonpolar F 2 molecules. Both HCl and F 2 consist of the same number of atoms and have approximately the same molecular mass. At a temperature of 150 K, molecules of both substances would have the same average KE. However, the dipole-dipole attractions between HCl molecules are sufficient to cause them to “stick together” to form a liquid, whereas the relatively weaker dispersion forces between nonpolar F 2 molecules are not, and so this substance is gaseous at this temperature. The higher normal boiling point of HCl (188 K) compared to F 2 (85 K) is a reflection of the greater strength of dipole-dipole attractions between HCl molecules, compared to the attractions between nonpolar F 2 molecules. We will often use values such as boiling or freezing points, or enthalpies of vaporization or fusion, as indicators of the relative strengths of IMFs of attraction present within different substances.
Dipole-Dipole Forces and Their Effects
Predict which will have the higher boiling point: N 2 or CO. Explain your reasoning.
Solution
CO and N 2 are both diatomic molecules with masses of about 28 amu, so they experience similar London dispersion forces. Because CO is a polar molecule, it experiences dipole-dipole attractions. Because N 2 is nonpolar, its molecules cannot exhibit dipole-dipole attractions. The dipole-dipole attractions between CO molecules are comparably stronger than the dispersion forces between nonpolar N 2 molecules, so CO is expected to have the higher boiling point.
Check Your Learning
Predict which will have the higher boiling point: ICl or Br 2 . Explain your reasoning.
ICl. ICl and Br 2 have similar masses (~160 amu) and therefore experience similar London dispersion forces. ICl is polar and thus also exhibits dipole-dipole attractions; Br 2 is nonpolar and does not. The relatively stronger dipole-dipole attractions require more energy to overcome, so ICl will have the higher boiling point.
Hydrogen Bonding
Nitrosyl fluoride (ONF, molecular mass 49 amu) is a gas at room temperature. Water (H 2 O, molecular mass 18 amu) is a liquid, even though it has a lower molecular mass. We clearly cannot attribute this difference between the two compounds to dispersion forces. Both molecules have about the same shape and ONF is the heavier and larger molecule. It is, therefore, expected to experience more significant dispersion forces. Additionally, we cannot attribute this difference in boiling points to differences in the dipole moments of the molecules. Both molecules are polar and exhibit comparable dipole moments. The large difference between the boiling points is due to a particularly strong dipole-dipole attraction that may occur when a molecule contains a hydrogen atom bonded to a fluorine, oxygen, or nitrogen atom (the three most electronegative elements). The very large difference in electronegativity (EN) between the H atom (EN=2.1) and the atom to which it is bonded (EN=4.0 for an F atom, EN=3.5 for an O atom, or EN=3.0 for a N atom), combined with the very small size of a H atom and the relatively small sizes of F, O, or N atoms, leads to highly concentrated partial charges with these atoms. Molecules with F-H, O-H, or N-H moieties are very strongly attracted to similar moieties in nearby molecules, a particularly strong type of dipole-dipole attraction called hydrogen bonding. Examples of hydrogen bonds include HF⋯HF, H 2 O⋯HOH, and H 3 N⋯HNH 2 , in which the hydrogen bonds are denoted by dots. Figure 9 illustrates hydrogen bonding between water molecules.
Despite use of the word “bond,” keep in mind that hydrogen bonds are intermolecular attractive forces, not intramolecular attractive forces (covalent bonds). Hydrogen bonds are much weaker than covalent bonds, only about 5 to 10% as strong, but are generally much stronger than other dipole-dipole attractions and dispersion forces.
Hydrogen bonds have a pronounced effect on the properties of condensed phases (liquids and solids). For example, consider the trends in boiling points for the binary hydrides of group 15 (NH 3 , PH 3 , AsH 3 , and SbH 3 ), group 16 hydrides (H 2 O, H 2 S, H 2 Se, and H 2 Te), and group 17 hydrides (HF, HCl, HBr, and HI). The boiling points of the heaviest three hydrides for each group are plotted in Figure 10 . As we progress down any of these groups, the polarities of the molecules decrease slightly, whereas the sizes of the molecules increase substantially. The effect of increasingly stronger dispersion forces dominates that of increasingly weaker dipole-dipole attractions, and the boiling points are observed to increase steadily.
If we use this trend to predict the boiling points for the lightest hydride for each group, we would expect NH 3 to boil at about −120 °C, H 2 O to boil at about −80 °C, and HF to boil at about −110 °C. However, when we measure the boiling points for these compounds, we find that they are dramatically higher than the trends would predict, as shown in Figure 11 . The stark contrast between our naïve predictions and reality provides compelling evidence for the strength of hydrogen bonding.
Effect of Hydrogen Bonding on Boiling Points
Consider the compounds dimethylether (CH 3 OCH 3 ), ethanol (CH 3 CH 2 OH), and propane (CH 3 CH 2 CH 3 ). Their boiling points, not necessarily in order, are −42.1 °C, −24.8 °C, and 78.4 °C. Match each compound with its boiling point. Explain your reasoning.
Solution
The VSEPR-predicted shapes of CH 3 OCH 3 , CH 3 CH 2 OH, and CH 3 CH 2 CH 3 are similar, as are their molar masses (46 g/mol, 46 g/mol, and 44 g/mol, respectively), so they will exhibit similar dispersion forces. Since CH 3 CH 2 CH 3 is nonpolar, it may exhibit only dispersion forces. Because CH 3 OCH 3 is polar, it will also experience dipole-dipole attractions. Finally, CH 3 CH 2 OH has an −OH group, and so it will experience the uniquely strong dipole-dipole attraction known as hydrogen bonding. So the ordering in terms of strength of IMFs, and thus boiling points, is CH 3 CH 2 CH 3 < CH 3 OCH 3 < CH 3 CH 2 OH. The boiling point of propane is −42.1 °C, the boiling point of dimethylether is −24.8 °C, and the boiling point of ethanol is 78.5 °C.
Check Your Learning
Ethane (CH 3 CH 3 ) has a melting point of −183 °C and a boiling point of −89 °C. Predict the melting and boiling points for methylamine (CH 3 NH 2 ). Explain your reasoning.
The melting point and boiling point for methylamine are predicted to be significantly greater than those of ethane. CH 3 CH 3 and CH 3 NH 2 are similar in size and mass, but methylamine possesses an −NH group and therefore may exhibit hydrogen bonding. This greatly increases its IMFs, and therefore its melting and boiling points. It is difficult to predict values, but the known values are a melting point of −93 °C and a boiling point of −6 °C.
Deoxyribonucleic acid (DNA) is found in every living organism and contains the genetic information that determines the organism’s characteristics, provides the blueprint for making the proteins necessary for life, and serves as a template to pass this information on to the organism’s offspring. A DNA molecule consists of two (anti-)parallel chains of repeating nucleotides, which form its well-known double helical structure, as shown in Figure 12 .
Each nucleotide contains a (deoxyribose) sugar bound to a phosphate group on one side, and one of four nitrogenous bases on the other. Two of the bases, cytosine (C) and thymine (T), are single-ringed structures known as pyrimidines. The other two, adenine (A) and guanine (G), are double-ringed structures called purines. These bases form complementary base pairs consisting of one purine and one pyrimidine, with adenine pairing with thymine, and cytosine with guanine. Each base pair is held together by hydrogen bonding. A and T share two hydrogen bonds, C and G share three, and both pairings have a similar shape and structure Figure 13 .
The cumulative effect of millions of hydrogen bonds effectively holds the two strands of DNA together. Importantly, the two strands of DNA can relatively easily “unzip” down the middle since hydrogen bonds are relatively weak compared to the covalent bonds that hold the atoms of the individual DNA molecules together. This allows both strands to function as a template for replication.
Key Concepts and Summary
The physical properties of condensed matter (liquids and solids) can be explained in terms of the kinetic molecular theory. In a liquid, intermolecular attractive forces hold the molecules in contact, although they still have sufficient KE to move past each other.
Intermolecular attractive forces, collectively referred to as van der Waals forces, are responsible for the behavior of liquids and solids and are electrostatic in nature. Dipole-dipole attractions result from the electrostatic attraction of the partial negative end of one dipolar molecule for the partial positive end of another. The temporary dipole that results from the motion of the electrons in an atom can induce a dipole in an adjacent atom and give rise to the London dispersion force. London forces increase with increasing molecular size. Hydrogen bonds are a special type of dipole-dipole attraction that results when hydrogen is bonded to one of the three most electronegative elements: F, O, or N.
Chemistry End of Chapter Exercises
1. a) In terms of their bulk properties, how do liquids and solids differ? b) How are they similar?
2. a) In terms of the kinetic molecular theory, in what ways are liquids similar to solids? b) In what ways are liquids different from solids?
3. a) In terms of the kinetic molecular theory, in what ways are liquids similar to gases? b) In what ways are liquids different from gases?
4. Explain why liquids assume the shape of any container into which they are poured, whereas solids are rigid and retain their shape.
5. What is the evidence that all neutral atoms and molecules exert attractive forces on each other?
6. Open the PhET States of Matter Simulation to answer the following questions:
(a) Select the Solid, Liquid, Gas tab. Explore by selecting different substances, heating and cooling the systems, and changing the state. What similarities do you notice between the four substances for each phase (solid, liquid, gas)? What differences do you notice?
(b) For each substance, select each of the states and record the given temperatures. How do the given temperatures for each state correlate with the strengths of their intermolecular attractions? Explain.
(c) Select the Interaction Potential tab, and use the default neon atoms. Move the Ne atom on the right and observe how the potential energy changes. Select the Total Force button, and move the Ne atom as before. When is the total force on each atom attractive and large enough to matter? Then select the Component Forces button, and move the Ne atom. When do the attractive (van der Waals) and repulsive (electron overlap) forces balance? How does this relate to the potential energy versus the distance between atoms graph? Explain.
7. Define the following and give an example of each:
(a) dispersion force
(b) dipole-dipole attraction
(c) hydrogen bond
8. The types of intermolecular forces in a substance are identical whether it is a solid, a liquid, or a gas. Why then does a substance change phase from a gas to a liquid or to a solid?
9. Why do the boiling points of the noble gases increase in the order He < Ne < Ar < Kr < Xe?
10. Neon and HF have approximately the same molecular masses.
(a) Explain why the boiling points of Neon and HF differ.
(b) Compare the change in the boiling points of Ne, Ar, Kr, and Xe with the change of the boiling points of HF, HCl, HBr, and HI, and explain the difference between the changes with increasing atomic or molecular mass.
11. Arrange each of the following sets of compounds in order of increasing boiling point temperature:
(a) HCl, H 2 O, SiH 4
(b) F 2 , Cl 2 , Br 2
(c) CH 4 , C 2 H 6 , C 3 H 8
(d) O 2 , NO, N 2
12. The molecular mass of butanol, C 4 H 9 OH, is 74.14; that of ethylene glycol, CH 2 (OH)CH 2 OH, is 62.08, yet their boiling points are 117.2 °C and 174 °C, respectively. Explain the reason for the difference.
13. On the basis of intermolecular attractions, explain the differences in the boiling points of n –butane (−1 °C) and chloroethane (12 °C), which have similar molar masses.
14. On the basis of dipole moments and/or hydrogen bonding, explain in a qualitative way the differences in the boiling points of acetone (56.2 °C) and 1-propanol (97.4 °C), which have similar molar masses.
15. The melting point of H 2 O( s ) is 0 °C. Would you expect the melting point of H 2 S( s ) to be −85 °C, 0 °C, or 185 °C? Explain your answer.
16. Silane (SiH 4 ), phosphine (PH 3 ), and hydrogen sulfide (H 2 S) melt at −185 °C, −133 °C, and −85 °C, respectively. What does this suggest about the polar character and intermolecular attractions of the three compounds?
17. Explain why a hydrogen bond between two water molecules is weaker than a hydrogen bond between two hydrogen fluoride molecules.
18. Under certain conditions, molecules of acetic acid, CH 3 COOH, form “dimers,” pairs of acetic acid molecules held together by strong intermolecular attractions:
Draw a dimer of acetic acid, showing how two CH 3 COOH molecules are held together, and stating the type of IMF that is responsible.
19. Proteins are chains of amino acids that can form in a variety of arrangements, one of which is a helix. What kind of IMF is responsible for holding the protein strand in this shape? On the protein image, show the locations of the IMFs that hold the protein together:
20. The density of liquid NH 3 is 0.64 g/mL; the density of gaseous NH 3 at STP is 0.0007 g/mL. Explain the difference between the densities of these two phases.
21. Identify the intermolecular forces present in the following solids:
(a) CH 3 CH 2 OH
(b) CH 3 CH 2 CH 3
(c) CH 3 CH 2 Cl
Glossary
- dipole-dipole attraction
- intermolecular attraction between two permanent dipoles
- dispersion force
- (also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together
- hydrogen bonding
- occurs when exceptionally strong dipoles attract; bonding that exists when hydrogen is bonded to one of the three most electronegative elements: F, O, or N
- induced dipole
- temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule
- instantaneous dipole
- temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically
- intermolecular force
- noncovalent attractive force between atoms, molecules, and/or ions
- polarizability
- measure of the ability of a charge to distort a molecule’s charge distribution (electron cloud)
- van der Waals force
- attractive or repulsive force between molecules, including dipole-dipole, dipole-induced dipole, and London dispersion forces; does not include forces due to covalent or ionic bonding, or the attraction between ions and molecules


1.1: Introduction
Chapter Objectives
After studying this chapter, you will be able to:
- Distinguish between anatomy and physiology, and identify several branches of each
- Describe the structure of the body, from simplest to most complex, in terms of the six levels of organization
- Identify the functional characteristics of human life
- Identify the four requirements for human survival
- Define homeostasis and explain its importance to normal human functioning
- Use appropriate anatomical terminology to identify key body structures, body regions, and directions in the body
- Compare and contrast at least four medical imaging techniques in terms of their function and use in medicine
Though you may approach a course in anatomy and physiology strictly as a requirement for your field of study, the knowledge you gain in this course will serve you well in many aspects of your life. An understanding of anatomy and physiology is not only fundamental to any career in the health professions, but it can also benefit your own health. Familiarity with the human body can help you make healthful choices and prompt you to take appropriate action when signs of illness arise. Your knowledge in this field will help you understand news about nutrition, medications, medical devices, and procedures and help you understand genetic or infectious diseases. At some point, everyone will have a problem with some aspect of their body and your knowledge can help you to be a better parent, spouse, partner, friend, colleague, or caregiver.
This chapter begins with an overview of anatomy and physiology and a preview of the body regions and functions. It then covers the characteristics of life and how the body works to maintain stable conditions. It introduces a set of standard terms for body structures and for planes and positions in the body that will serve as a foundation for more comprehensive information covered later in the text. It ends with examples of medical imaging used to see inside the living body.


15.3: Friction (Coulomb) Damped Free Vibrations
Friction can also provide vibration damping. In this case, however, the damping is not proportional to the magnitude of velocity. It only depends on the direction of velocity.
We remember from the section on dry friction that the force of friction in sliding depends only on the coefficient of kinetic friction, \(\mu_k\), and the normal force, \(F_N\).
\[ F_f = \mu_k F_N \]
The above equation does not include velocity. We know that kinetic friction acts to oppose motion, however, so a more complete expression would be:
\[F_f = - \text{sgn} (\dot{x}) \mu_k F_N , \]
where \(sgn\) is the "sign" function, a function that captures the sign (direction) of velocity. The above equation then indicates that the direction of friction is always opposite the direction of velocity, but the magnitude of velocity does not make a difference in the magnitude of friction.
The equation of motion of the system becomes:
\[ m \ddot{x} + \mu m g \ \text{sgn} (\dot{x}) + kx = 0, \]
and the solution to this equation of motion is:
\[ x(t) = \left( x_0 - \frac{(2n-1) \mu m g}{k} \right) \cos (\omega_n t) + \frac{\mu m g}{k} (-1)^{n+1} . \]
If we plot the response, we can see that there are several differences from a system with viscous damping.
Some differences when compared to viscous damping include:
- The system oscillates at the natural frequency of the system, not a damped natural frequency.
- The bounding curves are linear, not exponential.
- The system does not return to zero. This is because the magnitude of the friction force does not diminish as the system amplitude reduces, and at some point the spring force is no longer able to overcome the static friction that the system experiences when it changes direction (\(v=0\)).
Comparison to Viscous Underdamped System
If we consider our simple linear mass-spring system, the magnitude of \(F_f\) does not change with velocity, unlike with viscous damping. If we plotted both types of damping for the same system, we would get the following:
Note that the viscous damping has more reduction in amplitude earlier (despite relatively light damping), but continues oscillating past the point when the friction-damped system has stopped (specific relative values are dependent on the values of damping constant and coefficients of friction). Also note that since the viscous damping is relatively light, the difference in period between the two plots is quite small in this example.


 The sequence of motor skills first begins with
reflexes
. Infants are equipped with a number of reflexes, or involuntary movements in response to stimulation, and some are necessary for survival. These include the breathing reflex, or the need to maintain an oxygen supply (this includes hiccups, sneezing, and thrashing reflexes), reflexes that maintain body temperature (crying, shivering, tucking the legs close, and pushing away blankets), the sucking reflex, or automatically sucking on objects that touch their lips, and the rooting reflex, which involves turning toward any object that touches the cheek (which manages feeding, including the search for a nipple). Other reflexes are not necessary for survival, but signify the state of brain and body functions. Some of these include:the babinski reflex (toes fan upward when feet are stroked), the stepping reflex (babies move their legs as if to walk when feet touch a flat surface), the palmar grasp (the infant will tightly grasp any object placed in its palm), and the moro reflex (babies will fling arms out and then bring to chest if they hear a loud noise). These movements occur automatically and are signals that the infant is functioning well neurologically. Within the first several weeks of life, these reflexes are replaced with voluntary movements or motor skills.
Watch It
Watch this video to see examples of newborn reflexes.
A link to an interactive elements can be found at the bottom of this page.
Motor development occurs in an orderly sequence as infants move from reflexive reactions (e.g., sucking and rooting) to more advanced motor functioning. This development proceeds in a
cephalocaudal
(from head-down) and
proximodistal
(from center-out) direction. For instance, babies first learn to hold their heads up, then sit with assistance, then sit unassisted, followed later by crawling, pulling up, cruising, and then walking. As motor skills develop, there are certain developmental milestones that young children should achieve. For each milestone, there is an average age, as well as a range of ages in which the milestone should be reached. An example of a developmental milestone is a baby holding up its head. Babies on average are able to hold up their head at 6 weeks old, and 90% of babies achieve this between 3 weeks and 4 months old. If a baby is not holding up his head by 4 months old, he is showing a delay. On average, most babies sit alone at 7 months old. Sitting involves both coordination and muscle strength, and 90% of babies achieve this milestone between 5 and 9 months old (CDC, 2018). If the child is displaying delays on several milestones, that is a reason for concern, and the parent or caregiver should discuss this with the child’s pediatrician. Some developmental delays can be identified and addressed through early intervention.
Gross motor skills
are
voluntary movements that involve the use of large muscle groups and are typically large movements of the arms, legs, head, and torso. These skills begin to develop first. Examples include moving to bring the chin up when lying on the stomach, moving the chest up, rocking back and forth on hands and knees. But it also includes exploring an object with one’s feet as many babies do, as early as 8 weeks of age, if seated in a carrier or other device that frees the hips. This may be easier than reaching for an object with the hands, which requires much more practice (Berk, 2007). And sometimes an infant will try to move toward an object while crawling and surprisingly move backward because of the greater amount of strength in the arms than in the legs!
Fine Motor Skills
Fine motor skills
are more exact movements of the hands and fingers and include the ability to reach and grasp an object. These
skills
focus on the muscles in the fingers, toes, and eyes, and enable coordination of small actions (e.g., grasping a toy, writing with a pencil, and using a spoon). Newborns cannot grasp objects voluntarily but do wave their arms toward objects of interest. At about 4 months of age, the infant is able to reach for an object, first with both arms and within a few weeks, with only one arm. Grasping an object involves the use of the fingers and palm, but no thumbs. Stop reading for a moment and try to grasp an object using the fingers and the palm. How does that feel? How much control do you have over the object? If it is a pen or pencil, are you able to write with it? Can you draw a picture? The answer is, probably not. Use of the thumb comes at about 9 months of age when the infant is able to grasp an object using the forefinger and thumb (
the pincer grasp
). This ability greatly enhances the ability to control and manipulate an object, and infants take great delight in this newfound ability. They may spend hours picking up small objects from the floor and placing them in containers. By 9 months, an infant can also watch a moving object, reach for it as it approaches, and grab it. This is quite a complicated set of actions if we remember how difficult this would have been just a few months earlier.
Table 1. Timeline of Developmental Milestones.
[1]
[2]
Age
Developmental Milestone
~2 months
Can hold head upright on own
Smiles at sound of familiar voices and follows movement with eyes
As infants and children grow, their senses play a vital role in encouraging and stimulating the mind and in helping them observe their surroundings. Two terms are important to understand when learning about the senses. The first is
sensation
, or the interaction of information with the sensory receptors. The second is
perception
, or the process of interpreting what is sensed. It is possible for someone to sense something without perceiving it. Gradually, infants become more adept at perceiving with their senses, making them more aware of their environment and presenting more affordances or opportunities to interact with objects.
Vision
What can young infants see, hear, and smell? Newborn infants’ sensory abilities are significant, but their senses are not yet fully developed. Many of a newborn’s innate preferences facilitate interaction with caregivers and other humans. The womb is a dark environment void of visual stimulation. Consequently, vision is the most poorly developed sense at birth. Newborns typically cannot see further than 8 to 16 inches away from their faces, have difficulty keeping a moving object within their gaze, and can detect contrast more than color differences. If you have ever seen a newborn struggle to see, you can appreciate the cognitive efforts being made to take in visual stimulation and build those neural pathways between the eye and the brain.
Although vision is their least developed sense, newborns already show a preference for faces. When you glance at a person, where do you look? Chances are you look into their eyes. If so, why? It is probably because there is more information there than in other parts of the face. Newborns do not scan objects this way; rather, they tend to look at the chin or another less detailed part of the face. However, by 2 or 3 months, they will seek more detail when visually exploring an object and begin showing preferences for unusual images over familiar ones, for patterns over solids, faces over patterns, and three-dimensional objects over flat images. Newborns have difficulty distinguishing between colors, but within a few months are able to discrimination between colors as well as adults. Infants can also sense depth as binocular vision develops at about 2 months of age. By 6 months, the infant can perceive depth perception in pictures as well (Sen, Yonas, & Knill, 2001). Infants who have experience crawling and exploring will pay greater attention to visual cues of depth and modify their actions accordingly (Berk, 2007).
The infant’s sense of hearing is very keen at birth. If you remember from an earlier module, this ability to hear is evidenced as soon as the 5th month of prenatal development. In fact, an infant can distinguish between very similar sounds as early as one month after birth and can distinguish between a familiar and non-familiar voice even earlier. Babies who are just a few days old prefer human voices, they will listen to voices longer than sounds that do not involve speech (Vouloumanos & Werker, 2004), and they seem to prefer their mother’s voice over a stranger’s voice (Mills & Melhuish, 1974). In an interesting experiment, 3-week-old babies were given pacifiers that played a recording of the infant’s mother’s voice and of a stranger’s voice. When the infants heard their mother’s voice, they sucked more strongly at the pacifier (Mills & Melhuish, 1974). Some of this ability will be lost by 7 or 8 months as a child becomes familiar with the sounds of a particular language and less sensitive to sounds that are part of an unfamiliar language.
Pain and Touch
Immediately after birth, a newborn is sensitive to touch and temperature, and is also sensitive to pain, responding with crying and cardiovascular responses. Newborns who are
circumcised
(the surgical removal of the foreskin of the penis) without anesthesia experience pain, as demonstrated by increased blood pressure, increased heart rate, decreased oxygen in the blood, and a surge of stress hormones (United States National Library of Medicine, 2016). According to the American Academy of Pediatrics (AAP), there are medical benefits and risks to circumcision. They do not recommend routine circumcision, however, they stated that because of the possible benefits (including prevention from urinary tract infections, penile cancer, and some STDs) parents should have the option to circumcise their sons if they want to (AAP, 2012).
[3]
The sense of touch is acute in infants and is essential to a baby’s growth of physical abilities, language and cognitive skills, and socio-emotional competency. Touch not only impacts short-term development during infancy and early childhood but also has long-term effects, suggesting the power of positive gentle touch from birth. Through touch, infants learn about their world, bond with their caregiver, and communicate their needs and wants. Research emphasizes the great benefits of touch for premature babies, but the presence of such contact has been shown to benefit all children (Stack,
D. M. (
2010).
[4]
In an extreme example, some children in Romania were reared in orphanages in which a single care worker may have had as many as 10 infants to care for at one time. These infants were not often helped or given toys with which to play. As a result, many of them were developmentally delayed (Nelson, Fox, & Zeanah, 2014).
[5]
When we discuss emotional and social development later in this module, you will also see the important role that touch plays in helping infants feel safe and protected, which builds trust and secure attachments between the child and their caregiver.
Taste and Smell
Not only are infants sensitive to touch, but newborns can also distinguish between sour, bitter, sweet, and salty flavors and show a preference for sweet flavors. They can distinguish between their mother’s scent and that of others, and prefer the smell of their mothers. A newborn placed on the mother’s chest will inch up to the mother’s breast, as it is a potent source of the maternal odor. Even on the first day of life, infants orient to their mother’s odor and are soothed, when crying, by their mother’s odor (Sullivan et al., 2011).
[6]
The Centers for Disease Control and Prevention (CDC) describes the developmental milestones for children from 2 months through 5 years old. After reviewing the information, take the
CDC’s Developmental Milestones quiz
to see how well you recall what you’ve learned. If you are a parent with concerns about your child’s development, contact your pediatrician.
Glossary
cephalocaudal
refers to growth and development that occurs from the head down
circumcision
the surgical removal of the foreskin of the penis
fine motor skills
physical abilities involving small body movements, especially of the hands and fingers, such as drawing and picking up a coin. The word “fine” in this context means “small”
[glossary-term]gross motor skills: [/glossary-term]
[glossary-definition]physical abilities involving large body movements, such as walking and jumping. The word “gross” in this context means “big”[/glossary-definition]
motor skills
the word “motor” refers to the movement of the muscles. Motor skills refer to our ability to move our bodies and manipulate objects
perception
the process of interpreting what is sensed
pincer grasp
a developmental milestone that typically occurs at 9 to 12 months of age; the coordination of the index finger and thumb to hold smaller objects; represents a further development of fine motor skills
proximodistal
development that occurs from the center or core of the body in an outward direction
reflexes
the inborn, behavioral patterns that develop during uterine life and are fully present at birth. These are involuntary movements (not learned) or actions that are essential for a newborn’s survival immediately after birth and include: sucking, swallowing, blinking, urinating, hiccuping, and defecating
sensation
the interaction of information with the sensory receptors
Stack,
D. M. (
2010). Touch and Physical Contact during Infancy: Discovering the Richness of the Forgotten Sense. The Wiley-Blackwell Handbook of Infant Development, 532-567
<EMAIL_ADDRESS>Nelson, C. A., Fox, N. A., and Zeanah, C. H. (2014). Romania's abandoned children: Deprivation, brain development, and the struggle for recovery. Cambridge, MA, and London, England: Harvard University Press.
<EMAIL_ADDRESS>Sullivan, R., Perry, R., Sloan, A., Kleinhaus, K., & Burtchen, N. (2011). Infant bonding and attachment to the caregiver: insights from basic and clinical science. Clinics in perinatology, 38(4), 643–655. doi:10.1016/j.clp.2011.08.011
<EMAIL_ADDRESS>Modification, adaptation, and original content.
Authored by
: Tera Jones for Lumen Learning.
Provided by
: Lumen Learning.
License
:
CC BY: Attribution


6.5: Social Institutions
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- Last updated
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- Erika Gutierrez, Janét Hund, Shaheen Johnson, Carlos Ramos, Lisette Rodriguez, & Joy Tsuhako
- Long Beach City College, Cerritos College, & Saddleback College via ASCCC Open Educational Resources Initiative (OERI)
(White) Social Institutions
In his seminal work, Racism Without Racists, Eduardo Bonilla-Silva surmises that liberal social thought informs our (white) perspective on the world and justifies our (white) social, economic & political institutions. Bonilla-Silva's parenthesis of white is intentional in that liberal white social thought equates with colorblindness whereby we consider cultural differences as meaningless. As white is the default within our society, it has been made to seem normal. However, scholars of critical race theory seek to call attention to how whiteness has been structured into the fabric of society, particularly our social institutions. In their dissection of critical race theory, Richard Delgado and Jean Stefancic (2001) include one of the key elements of critical race theory is that "our system of white-over-color ascendancy serves important purposes, both psychic and material." A century before, W.E.B. DuBois had coined this as the wage of whiteness.
Research shows the distribution of resources and opportunities are not equal among racial and ethnic categories, and white groups do better than other groups (Konrad & Schmidt, 2004). Regardless of social perception, in reality, there are institutional and cultural differences in government, education, criminal justice, sports, the workplace, and mass media media and racial-ethnic groups have received subordinate roles and treatment in society. These social institutions are generally controlled by white Americans. Certainly, these institutions were created by white Americans. Though we may access these social institutions in our everyday lives to a greater or lesser degree, we certainly do not all have equal control over these institutions.
In White Fragility, Robin DiAngelo presents the following statistics which help to understand how our social institutions reflect white dominance:
Figure \(\PageIndex{1}\): White Dominance in the U.S. (Chart by Jonas Oware with data from White Fragility)
| Category | % white |
|---|---|
| 10 Richest Americans | 100% |
| U.S. Congress | 90% |
| U.S. Governors | 96% |
| Top Military Advisors |
100% |
| Current U.S. President & Vice-President | 100% |
| Current U.S. Presidential Cabinet | 91% |
| People Who Decide Which TV Shows We See | 93% |
| People Who Decide Which Books We Read | 90% |
| People Who Decide Which News is Covered | 85% |
| People Who Decide Which Music is Produced | 95% |
| People Who Directed the 100 Top Grossing Films Worldwide | 95% |
| Teachers | 82% |
| Full-Time College Professors | 84% |
| Owners of Men's Professional Football Teams | 97% |
White Americans on average have far greater wealth than other race-ethnic groups. All U.S. Presidents except Barack Obama have been white men. The U.S. Congress remains disproportionately white (men) as are Fortune 500 CEOs. Even the Oscars have been called out for being overwhelming white (#OscarsSowhite). This is significant considering not only the billion dollar media consumption in the U.S., but also the global consumption of U.S. mass media. All of this "business as usual" in our (white) social institutions adds up, to cumulative, systemic benefits for white Americans.
Sports
Take professional sports as a first example. Based on data gathered by The Institute for Diversity and Ethics in Sports, the following tables reveal the imbalance of who the players are versus who the coaches, owners, and/Chief Executive Officers (CEOs) are of the National Basketball Association (NBA) and National Football Association (NFL) (Lapchick, 2019). Clearly, the majority of players are of color whereas the majority of the owners or CEOs are white. The NBA has made more progress than the NFL with regards to hiring more head coaches of color, but clearly the majority of coaches in either sport remain white. It must be noted that during the 2020 protests against racial injustice, the NFL Commissioner has stated his verbal support for Black Lives Matter, which is a striking contrast from only a few years prior when quarterback Colin Kapernick was ostracized for taking a knee during the national anthem to call attention to racial injustice. In the summer of 2020, most NBA teams, including players, coaches, referees, and owners, have not only taken a knee during the national anthem, but many players were slogans on their jerseys supporting the movement (e.g. Black Lives Matter, Vote, Ally, Equality).
| Players | Head Coaches | Majority Owners | League Office Staff | |
|---|---|---|---|---|
| White | 18.1% | 66.7% | 91.4% | 62.4% |
| African-American | 74.8% | 26.7% | 2.9% | 15.9% |
| Latino | 2.4% | 3.3% | 0% | 6.7% |
| Asian | >1% | 3.3% | 2.9% | 10,4% |
| Other | 3.9% | 0% | 2.9% | 4.6% |
| Players | Head Coaches | CEO/President | League Office Staff | |
|---|---|---|---|---|
| White | 26.8% | 81.3% | 95% | 67.3% |
| African-American | 58.9% | 9.4% | 0% | 10.2% |
| Latino | .5% | 3.1% | 0% | 6.6% |
| AAPI | 1.6% | 0% | 4.9% | 9.3% |
| AI/AN | 0% | 0% | 0% | .1% |
| Two or more races | 9.6% | 0% | 0% | 1.7% |
| Not disclosed | 3.1% | 4.7% |
Education
A second example is education. Gall-Peters Projection calls attention to the content of our K-12 education which favors a Eurocentric lens when presenting history and geography. Eurocentrism is a worldview that is centered on or favors Western, often white, civilization. For decades we have seen inequitable student outcomes both in K-12 and in higher education which can be in part attributed to the Eurocentric curriculum. Gloria Ladson-Billings and William Tate’s (1995) seminal writing on critical race theory of education examined how school inequities emanate from a racialized society. Christine Stanley (2006) presented one of the key arguments in critical race theory, that the subtleties of institutional racism are rarely acknowledged publicly, particularly by the dominant Euro-American culture. Stanley (2006) further stated, “Many institutions value diversity, but they often do not look deep enough to ascertain how habitual policies and practices work to disadvantage certain social, racial or cultural groups” (p. 724).
Criminal Justice System
A third example is the criminal justice system. White Americans are underrepresented in our prisons, while African Americans are disproportionately incarcerated. Michelle Alexander writes in The New Jim Crow that the criminal justice system, especially prison, is specifically designed as a form of social control over African American men. Most recent U.S.Presidents beginning with Nixon have used the campaign phrase "law and order" which is ultimately a code word for the racial control of people of color, as presented convincingly in the documentary, 13th . The school-to-prison pipeline is used to explain the disheartening statistics for young people of color, particularly African American males, who are overrepresented in prison and underrepresented in higher education. Most of our schools and prisons are also run by white male or female principals, presidents, or wardens.
Workplace/Economy
Finally, let us consider how the the workplace, situated in the social institution of our economy, often fosters a climate of white supremacy, though we may be entirely unaware that it is at play. As Kenneth Jones and Tema Okun (2001) present, the following characteristics of white supremacy culture show up in organizations such as the workplace:
- perfectionism
- sense of urgency
- defensiveness
- quantity over quality
- worship of the written word
- only one right way
- paternalism
- either/or thinking
- power hoarding
- fear of open conflict
- individualism
- progress is bigger/more
- objectivity
- right to comfort those with power
The characteristics listed above are damaging because they are used as norms and standards without actually being selected by the group members. They are damaging because they promote hegemonic, white supremacist thinking. They are damaging to both people of color and to white people because they detract from our humanity and our capacity to value difference. These characteristics may be prevalent in a predominantly white institutions (PWI) or in organizations led by people of color.
By listing characteristics of white supremacy culture, we point out how organizations unconsciously use these characteristics as their norms and standards, thereby making it difficult, if not impossible, to open the door to other cultural norms, standards, practices, and ways of leading. These practices inhibit a truly multicultural organization; Section 6.6 considers antidotes to these practices.
Thinking Sociologically
Consider these questions posed by Kenneth Jones and Tema Okun (2001) in Dismantling Racism: A Workbook for Social Change Groups:
Which of these characteristics of white supremacy culture are at play in your workplace or other organizations in your community? How do they stand in the way of racial justice? What can you and your community do to shift the belief(s) and behavior(s) to ones that support racial justice and a multicultural organization?
Web of Institutional Racism
Previously discussed in Chapter 4.4 , institutional racism can be understood simply as "business as usual." It is business as usual that people of color tend to be underrepresented in powerful positions in the aforementioned social institutions; conversely, it is business as usual that white Americans tend to be in positions of power in our major social institutions - though it is easier to point out exceptions to that rule in the past 30 years as opposed to the rest of U.S. history.
Institutional racism is the policies and practices within institutions that benefit white people to the disadvantage of people of color. An example of institutional racism is how children of color are treated within the U.S. education system. On average, children of color are disciplined more harshly than their white peers. They are also less likely to be identified as gifted and have less access to quality teachers. Racism in schools can and does have severe consequences for students and our future (National Museum of African American History and Culture).
Shirley Better explains the web of institutional racism which is rooted in housing inequality which in turn impacts educational, employment, health, and criminal justice outcomes. Housing patterns in the 20th century served to provide opportunities for mobility for white Americans, to the detriment of communities of color, particularly African African Americans. After WWII, the GI bill provided white veterans incentives to own their own homes in the suburbs. Communities which used restricted covenants offered only whites the opportunity to own homes and property in these restricted neighborhoods. This government-funded segregation cemented wealth for white Americans. On the other hand, African Americans experienced redlining (inability to get standard mortgages in African American neighborhoods), steering (swayed away from home ownership in white neighborhoods), substandard public housing, white flight (white mobility from neighborhoods in which African Americans were moving in) and gentrification (replacing poor neighborhoods with middle class individuals).
As home ownership is the traditional, tried and true key to accessing wealth in the U.S., it becomes easier to understand the web of institutional racism that Better describes. Where we live generally determines where our children attend school. The quality of schooling we receive impacts our potential for higher education, our entrance into the job market, and quite possible our interactions with police and the criminal justice system. Additionally, the type of job we work generally determines the type of health care we receive or do not receive.
Key Takeaways
- Social institutions such as sports, education, criminal justice system, and the workplace reflect white dominance.
- The web of institutional racism, rooted in housing inequality, negatively impacts educational, employment, health, and criminal justice outcomes for many communities of color, while simultaneously advantaging Euro Americans/white Americans.
Contributors and Attributions
- Hund, Janét. (Long Beach City College)
- Johnson, Shaheen. (Long Beach City College)
- Minority Studies (Dunn) ( CC BY 4.0 )
Works Cited
- Alexander, M. (2010). The New Jim Crow: Mass Incarceration in the Age of Colorblindness. New York, NY: New Press.
- Better, S. (2007). Institutional Racism: A Primer on Theory and Strategies for Social Change. 2nd ed. Lanham, MD: Rowman & Littlefield Publishers.
- Delgado, S. & Stefancic, J. (2001). Critical Race Theory. New York, NY: New York University Press.
- Bonilla-Silva, E. (2001). W hite Supremacy and Racism in the Post Civil Rights Era. Boulder, CO: Lynne Reinner Publishers.
- DiAngelo, R. (2018). W hit e Fragility: Why It's So Hard for white People to Talk about Racism. Boston, MA: Beacon Press.
- Du Bois, W.E.B. (1977). [1935]. Black Reconstruction: An Essay Toward a History of the Part which Black Folk Played in the Attempt to Reconstruct Democracy in America, 1860 -880 . Atheneum, NY.
- Duvernay, A. & Moran, J. (2016). 13th . [Motion picture]. Kandoo Films.
- Gall-Peters Projection. Wikipedia.
- Jones, K. & Okun, T. (2001). Dismantling Racism: A Workbook for Social Change Groups. ChangeWork.
- Ladson-Billings, G. & Tate, W. (1995, Fall). Toward a critical race theory of education. Teachers College Record, 97(1), 47-68.
- Konradi, A. & Schmidt, M. (2004). Reading Between the Lines: Toward an Understanding of Current Social Problems. 3rd ed. New York, NY: McGraw-Hill.
- Lapchick, R. (2019, October 30). The 2019 racial and gender report card: national football league. The Institute for Diversity and Ethics in Sport.
- Lapchick, R. (2019, June 18). The 2019 racial and gender report card: national basketball association. The Institute for Diversity and Ethics in Sport.
- National Museum of African American History and Culture. (n.d.). Talking about race: being anti-racist.
- Stanley, C.A. (2006). Coloring the academic landscape: Faculty of color breaking the silence in predominantly white colleges and universities. American Educational Research Journal, 43 (4), 701–736.


4.12: Common Frameworks for Evaluating the Business Environment
- Explain environmental scanning and the PESTEL checklist for a company’s general environment.
- Explain the impact of Porter’s “five forces” on industry profits.
- Explain competitor analysis.
Introduction
The environment is always changing, and this is just as true for the business environment as it is for the physical world around us. Managers try to avoid being “taken by surprise” by unexpected events that would impact their organizations through an ongoing process called environmental scanning . Environmental scanning is a high-level, broad-based process of gathering, analyzing, and dispensing information for purpose of developing strategies or tactics. The process entails getting both factual data and qualitative opinions. Organizations also scan when they are considering whether to enter a particular industry.
PESTEL
You may wonder just how you go about analyzing the total external environment that would affect your company. A commonly used management tool is called PESTEL. PESTEL is an organizing framework that allows decision makers to understand and make connections with a mass of information. (You may sometimes see the name of this tool written as PESTLE or even just PEST in older sources.)
A PESTEL analysis examines six key macro-environmental factors in order to understand their interactions with the organization.
Besides alerting top management to potential threats in the environment, a PESTEL analysis is a part of the external strategic analysis when conducting research into new markets. It gives an overview of the different macro-environmental factors that the company has to take into consideration. Descriptions of the six key PESTEL factors follow.
Political
Political issues are a function of how much the government intrudes or is involved in an organization’s operations. In particular, it looks at taxation and tariffs, regulations, political stability, and elections. For example, Google and other Internet providers have financial, legal, and ethical issues relating to operating in countries like China or Iran, where repressive governments want to control the flow of information. In another example, Google was slapped with a $2.7 billion fine by the European Union for antitrust abuses (Google can appeal this decision with the European Court of Justice). Finally, the CEO of Apple is awaiting changes in the tax law before bringing almost $250 billion in foreign reserves back to the United States. Often, decision makers for these organizations must choose between making money or suppressing information critical of the repressive regimes.
Economic
Economic factors start with indicators for the U.S. economy as a whole. These are growth, employment, inflation, and interest rates. Companies with foreign operations will worry about exchange rates. These factors are important in long-range forecasts for revenue and expenses. Businesses in the financial industry may pull back from aggressive strategies in times of rising interest rates.
Social
Society and culture have great impacts on the business environment. These factors include demographics like population growth, age distribution, and attitudes toward safety and health consciousness. For example, rising rates of obesity have forced management to look closely at marketing campaigns in giant food corporations such as Nestle and Kraft Foods.
Technological
Technology facts include research and development (R&D), automation and robotics, and technology incentives. The rate of technological change in the business environment is staggering. A term often paired with technology is disruption , a description for innovations that completely change the cast of leading competitors in an industry. Many organizations not only scan the technological environment but also monitor closely for new and disruptive processes. Walt Disney and Alphabet (Google’s parent corporation) are both investing heavily to become leaders in virtual reality. They are betting billions that augmented reality will have the power to disrupt the gaming and entertainment industries.
Environmental
Weather, climate change, air quality, and natural disasters are all environmental factors. Some industries are especially at risk from changes in the natural environment, including manufacturing, agriculture, tourism and travel, and sports and entertainment. Many pollution regulations limiting water and air pollution have been passed that affect the operation of businesses. Today, the impact of climate control is being debated in Congress, and organizations in many industries are concerned how this latest environmental threat will affect their operations. Recently, Shell Oil spent more than $7 billion exploring parts of the Arctic Circle for oil—a venture that was not possible before global warming increased drilling access in the area. They have since cancelled this initiative due to a lack of results, as well as strong international protests that it may cause further damage to an environmentally sensitive location.
Legal
Legal factors include discrimination laws, consumer protection laws, and employment, health, and safety policies. Antitrust, piracy and copyright laws, as well as immigration issues are also of growing importance in the business environment. All of these factors affect how organizations operate, their costs, and the demand for products. For example, after the collapse of Enron, the government passed the Sarbanes-Oxley Act in 2002. This legislation completely changed accounting and reporting requirements for corporations. These businesses have had to implement rigorous procedures to ensure compliance with the new regulations. After the Great Recession of 2008–2009, Congress passed the Dodd-Frank Act, which greatly increased regulations and oversight for banks and other financial firms. Bank lobbyists successfully slowed the implementation of many rules, but compliance costs doubled and totaled $70 billion in 2016.
Porter’s Five Forces
Michael Porter, a well-known business consultant and professor at Harvard University, identified five critical external factors that affect strategies being developed by organizations in any industry. This system, known as Porter’s Five Forces , has become an important management strategy tool. Managers use the tool to examine opportunities and threats and to facilitate decision making in the context of their company’s external environment. It measures the competitiveness of an industry and thus its attractiveness or potential profitability. An unattractive industry is one in which the combination of these five forces acts to drive down overall profitability.
The five forces defined by Porter include:
- The threat of new entrants (or barriers to entry). This refers to the threat that new competitors pose to the existing businesses in an industry. A profitable industry will attract new competitors. If it is easy for new businesses to enter the industry, then the businesses already operating in the industry are at a greater risk. There may be a high threat of new entrants to an industry when brand names are not well-known, when it is easy for customers to switch to a new supplier, and when trademarks or copyrights are not involved in the production process. For example, it would be very hard to enter an industry such as airlines, which requires a huge financial investment to pay for equipment, personnel, and airport gateways.
- The threat of substitute products or services . A substitute product is not a similar product from a competitor, but rather a different product or service altogether but that performs the same purpose in the mind of the consumer. For example, a city subway system could be a substitute product to an automobile manufacturer. Likewise, e-mails may substitute for writing letters, olive oil may be a butter substitute, and tea may substitute for coffee. If there are good substitutes to a product, the industry is less profitable.
- Competitive rivalry within the industry . Porter believes that the intensity or the level of competition in an industry is one of the main forces that determines the profitability of that industry. A highly competitive market suggests that the competitors are aggressively trying to take market share from their rivals. Intensity can be affected by the number of competitors, the size of the market, the growth of the industry, and how difficult it is to differentiate your product (make it unique in some major feature). The airline and automotive industries are examples of high rivalry industries.
- The bargaining power of buyers. Buyer bargaining power refers to the amount of pressure customers can put on a seller. The buyer wants to lower prices, increase service, or improve the quality of the product. From the viewpoint of the seller, an industry where the buyer has high bargaining power is not particularly attractive because competitors will have many possible strategies for easily taking the customer away. High buying bargaining power decreases potential profits if the seller responds to the buyers’ tactics. Remember that the buyer is not always a consumer; many businesses sell to other businesses who also have buyer bargaining power. A company like Walmart has a lot of buyer bargaining power because of the extremely high volume of its purchases.
- The bargaining power of suppliers. Supplier bargaining power is another force that shapes the competitive measure of an industry because it limits the ability of the seller to make a profit. Powerful suppliers can pressure buyers by raising prices, lowering quality, or reducing the availability of the supply.
An important thing to remember about Porter’s Five Forces is that it is useful at an industry level and not for groups or segments of a market. It is also a “snapshot” of what the industry looks like at a particular time and needs to be updated regularly. And as with any management tool, it is not perfect and infallible. When considered as a starting point for discussion and further investigation, however, Porter’s Five Forces is very useful.
Competitive Analysis
Earlier in this module, you read about the concept of competitive advantage. You learned that knowing the strengths and weaknesses of your competitors are key elements in devising organizational goals and determining strategies to meet the goals.
Once the external business environment has been analyzed for its suitability, industry competitors must be profiled to determine who your specific competitors are. Not all “players” in an industry will be in direct competition with your organization. (You don’t want to spend valuable resources on an in-depth competitive analysis of BMW and Mercedes if you sell Hyundais.) A robust competitive analysis will allow you to focus on those companies that will compete for customers in your target market.
A competitive analysis looks at competitors and tries to answer such questions as these in the following categories:
- General Background : Who are my competitors? Where are they located? Who are the key personalities? What type of organizational structure is it?
- Financial : How profitable are they? Have they grown in the recent past? And any other data you can ethically discover.
- Products : What products do they sell? Have they introduced new products and what is their success rate? What brands do they carry? Do they hold patents and licenses?
- Customers: What market segment do they serve? What is the customer growth rate? How strong is the customer loyalty?
- Advertising and Sales: What are their distribution channels? What is their promotional strategy? How large is their sales force? What is their pricing and discount structure?
- Personnel: How many employees do they have? What is their compensation package including benefits? What kind of managers and what management style do they show? More importantly, what skills is the competition hiring? If a company is hiring experts in artificial intelligence, it tells the competition quite a bit about the plans for the future.
There are many more questions that would be relevant to this kind of in-depth analysis. The more you know about your competition, the better prepared you will be when you go up against it. The next section will identify industry components that affect your ability to operate. It will introduce tools that allow organizations to focus on only the specific internal and external features that affect them.
Contributors and Attributions
- Frameworks for Evaluating the Business Environment. Authored by : John/Lynn Bruton and Lumen Learning. License : CC BY: Attribution
- Open sign. Authored by : wndj. Located at : https://pixabay.com/en/sign-open-open-sign-business-store-1781609/ . License : CC0: No Rights Reserved
- Porters five forces. Authored by : Grahams Child. Located at : https://commons.wikimedia.org/wiki/File:Porters_five_forces.PNG . License : CC BY-SA: Attribution-ShareAlike


12.1: Stress and Strain
Rocks are subject to stress —mostly related to plate tectonics but also to the weight of overlying rocks—and their response to that stress is strain (deformation). In regions close to where plates are converging stress is typically compressive—the rocks are being squeezed. Where plates are diverging the stress is extensive—rocks are being pulled apart. At transform plate boundaries, where plates are moving side by side there is sideways or shear stress —meaning that there are forces in opposite directions parallel to a plane. Rocks have highly varying strain responses to stress because of their different compositions and physical properties, and because temperature is a big factor and rock temperatures within the crust can vary greatly.
We can describe the stress applied to a rock by breaking it down into three dimensions—all at right angles to one-another (Figure \(\PageIndex{1}\)). If the rock is subject only to the pressure of burial, the stresses in all three directions will likely be the same. If it is subject to both burial and tectonic forces, the pressures will be different in different directions.
Rock can respond to stress in three ways: it can deform elastically, it can deform plastically, and it can break or fracture. Elastic strain is reversible; if the stress is removed, the rock will return to its original shape just like a rubber band that is stretched and released. Plastic strain is not reversible. As already noted, different rocks at different temperatures will behave in different ways to stress. Higher temperatures lead to more plastic behaviour. Some rocks or sediments are also more plastic when they are wet. Another factor is the rate at which the stress is applied. If the stress is applied quickly (for example, because of an extraterrestrial impact or an earthquake), there will be an increased tendency for the rock to fracture. Some different types of strain response are illustrated in Figure \(\PageIndex{2}\).
The outcomes of placing rock under stress are highly variable, but they include fracturing, tilting and folding, stretching and squeezing, and faulting. A fracture is a simple break that does not involve significant movement of the rock on either side. Fracturing is particularly common in volcanic rock, which shrinks as it cools. The basalt columns in Figure \(\PageIndex{3}\)a are a good example of fracture. Beds are sometimes tilted by tectonic forces, as shown in Figure \(\PageIndex{3}\)b, or folded as shown in Figure \(\PageIndex{1}\).
When a body of rock is compressed in one direction it is typically extended (or stretched) in another. This is an important concept because some geological structures only form under compression, while others only form under tension. Most of the rock in Figure \(\PageIndex{3}\)c is limestone, which is relatively easily deformed when heated. The dark rock is chert, which remains brittle. As the limestone stretched (parallel to the hammer handle) the brittle chert was forced to break into fragments to accommodate the change in shape of the body of rock. A fault is a rock boundary along which the rocks on either side have been displaced relative to each other (Figure \(\PageIndex{3}\)d).
Media Attributions
- Figures 12.1.1, Figure \(\PageIndex{2}\), Figure \(\PageIndex{3}\): © Steven Earle. CC BY.


12: Western Europe and Byzantium circa 1000-1500 CE
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- 12.7: Growth in Agriculture
- Eleventh-century Europe’s economy was primarily agricultural. The eleventh and twelfth centuries saw a massive expansion of agricultural output in the northern regions of Europe, which led to a corresponding growth in the economy and population. The same improvement in iron technology that allowed the equipping of armored knights led to more iron tools: axes allowed farmers to clear forests and cultivate more land, and the iron share of a heavy plow allowed farmers to plow deep into thick soil.
Thumbnail: Baldwin of Boulogne entering Edessa in 1098 (history painting, Joseph-Nicolas Robert-Fleury 1840). (Public Domain).