4.2: Layers of the Skin
By the end of the section, you will be able to:
- Identify the components of the integumentary system
- Describe the layers of the skin and the functions of each layer
- Identify and describe the hypodermis and deep fascia
- Describe the role of keratinocytes and their life cycle
- Describe the role of melanocytes in skin pigmentation
Although you may not typically think of the skin as an organ, it is in fact made of tissues that work together as a single structure to perform unique and critical functions. The skin and its accessory structures make up the integumentary system , which provides the body with overall protection. The skin is made of multiple layers of cells and tissues, which are held to underlying structures by connective tissue (Figure \(\PageIndex{1}\)). The superficial layer, known as the epidermis , is composed primarily of tightly pack epithelial cells. The deeper layer of skin, the dermis , is well vascularized (has numerous blood vessels) and is where several accessory structures, such as hair follicles, sweat glands, and oil glands, can be found. It also has numerous sensory, and autonomic and sympathetic nerve fibers ensuring communication to and from the brain. Below the dermis lies the superficial fascia, or hypodermis , which is not technically part of the skin, but serves to connect the skin to the underlying fascia. This layer is mainly composed of loose, areolar and adipose connective tissues.
The Epidermis
The epidermis is composed of keratinized, stratified squamous epithelium. It is made of four or five layers of epithelial cells, depending on its location in the body. It does not have any blood vessels within it (i.e., it is avascular). Skin that has four layers of cells is referred to as “thin skin.” From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. Most of the skin can be classified as thin skin. “Thick skin” is found only on the palms of the hands and the soles of the feet. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and the stratum granulosum (Figure \(\PageIndex{2}\)).
The majority of cells in the epidermis are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin. Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers.
Stratum Basale
The stratum basale (also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The cells in the stratum basale bond to the dermis via intertwining collagen fibers, referred to as the basement membrane. A finger-like projection, or fold, known as the dermal papilla (plural = dermal papillae) is found in the superficial portion of the dermis. Dermal papillae increase the strength of the connection between the epidermis and dermis; the greater the surface area conveyed by folding, the stronger the connections made (Figure \(\PageIndex{3}\)).
The stratum basale is a single layer of cells primarily made of basal cells. A basal cell is a cuboidal-shaped stem cell that is a precursor of the keratinocytes of the epidermis. All of the keratinocytes are produced from this single layer of cells, which are constantly going through mitosis to produce new cells. As new cells are formed, the existing cells are pushed superficially away from the stratum basale. Two other cell types are found dispersed among the basal cells in the stratum basale. The first is a Merkel cell, also known as a tactile cell, which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The second is a melanocyte , a cell that produces the pigment melanin. Melanin gives hair and skin its color, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage.
In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.
Stratum Spinosum
As the name suggests, the stratum spinosum is spiny in appearance due to the protruding cell processes that join the cells via an anchoring junction common in epithelial tissues called a desmosome . The desmosomes interlock with each other and strengthen the bond between the cells. It is interesting to note that the “spiny” nature of this layer is an artifact of the staining process. Unstained epidermis samples do not exhibit this characteristic appearance. The stratum spinosum is composed of eight to ten layers of keratinocytes, formed as a result of cell division in the stratum basale (Figure \(\PageIndex{4}\)). The keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid that helps prevent water loss from the body, making the skin relatively waterproof. As new keratinocytes are produced atop the stratum basale, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. Wandering among the keratinocytes of this layer is a type of dendritic cell called the Langerhans cell , also known as a dendritic cell, which differentiates from and functions similarly to a macrophage by engulfing bacteria, foreign particles, and damaged cells that occur in this layer.
Stratum Granulosum
The stratum granulosum has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum. The cells here (three to five layers thick) become flatter, their cell membranes thicken with a coating of lipids secreted by accumulated lamellar granules , and they generate large amounts of the fibrous proteins keratin, incorporating intermediate filaments of the cytoskeleton with filaggrin derived from proteins secreted by accumulated keratohyalin granules (see Figure \(\PageIndex{3}\)). These proteins of the late stages of keratin synthesis account for the bulk of the keratinocyte mass in the stratum granulosum. The accumulated granules give the layer its grainy appearance. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin and coated cell membranes that will form the stratum lucidum, the stratum corneum, and the accessory structures of hair and nails.
Stratum Lucidum
The stratum lucidum is a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum. This thin layer of cells is found only in the thick skin of the palms, soles, and digits. The keratinocytes that compose the stratum lucidum are dead and flattened (see Figure \(\PageIndex{3}\)). These cells are densely packed with eleiden , a clear protein rich in lipids, derived from keratohyalin, which gives these cells their transparent (i.e., lucid) appearance and provides a barrier to water.
Stratum Corneum
The stratum corneum is the most superficial layer of the epidermis and is the layer exposed to the outside environment (see Figure \(\PageIndex{3}\)). The increased keratinization (also called cornification) of the cells in this layer gives it its name. There are usually 15 to 30 layers of cells in the stratum corneum. This dry, dead layer helps prevent the penetration of microbes and the dehydration of underlying tissues, and provides a mechanical protection against abrasion for the more delicate, underlying layers. Cells in this layer are shed periodically and are replaced by cells pushed up from the stratum granulosum (or stratum lucidum in the case of the palms and soles of feet). The entire layer is replaced during a period of about 4 weeks. Cosmetic procedures, such as microdermabrasion, help remove some of the dry, upper layer and aim to keep the skin looking “fresh” and healthy.
Dermis
The dermis might be considered the “core” of the integumentary system (derma- = “skin”), as distinct from the epidermis (epi- = “upon” or “over”) and hypodermis (hypo- = “below”). It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue, the superficial papillary layer and deep reticular layer , that compose an interconnected mesh of elastic and collagen fibers, produced by fibroblasts (Figure \(\PageIndex{5}\)).
Papillary Layer
The papillary layer is made of loose, areolar connective tissue, which means the collagen and elastic fibers of this layer form a loose mesh. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae (see Figure \(\PageIndex{5}\)).  These small blood vessels form the subpapillary plexus, found just below the dermal papillae, which branch into the capillary beds that supply blood to the dermal papillae. In addition, the papillary layer contains phagocytes, defensive cells that help fight bacteria or other infections that have breached epidermis. This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles. Also known as tactile corpuscles, Meissner corpuscles can be found located in the dermal papillae, and are responsible for sensing light touch. More details on the sensory functions of skin are covered later in this chapter.
Reticular Layer
Underlying the papillary layer is the much thicker reticular layer , composed of dense irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. The reticular layer appears reticulated (net-like) due to a tight meshwork of fibers. Elastic fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated. Collagen injections and Retin-A creams help restore skin turgor by either introducing collagen externally or stimulating blood flow and repair of the dermis, respectively.
Hypodermis
The hypodermis (also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the skin.
EVERYDAY CONNECTION
Lipid Storage
The hypodermis is home to most of the fat that concerns people when they are trying to keep their weight under control. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma.
Where the fat is deposited and accumulates within the hypodermis depends on hormones (testosterone, estrogen, insulin, glucagon, leptin, and others), as well as genetic factors. Fat distribution changes as our bodies mature and age. Men tend to accumulate fat in different areas (neck, arms, lower back, and abdomen) than do women (breasts, hips, thighs, and buttocks). The body mass index (BMI) is often used as a measure of fat, although this measure is, in fact, derived from a mathematical formula that compares body weight (mass) to height. Therefore, its accuracy as a health indicator can be called into question in individuals who are extremely physically fit.
In many animals, there is a pattern of storing excess calories as fat to be used in times when food is not readily available. In much of the developed world, insufficient exercise coupled with the ready availability and consumption of high-calorie foods have resulted in unwanted accumulations of stored lipids in adipose tissue in many people. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat. Recent studies indicate that a distressing percentage of our population is overweight and/or clinically obese. Not only is this a problem for the individuals affected, but it also has a severe impact on our healthcare system. Changes in lifestyle, specifically in diet and exercise, are the best ways to control body fat accumulation, especially when it reaches levels that increase the risk of heart disease and diabetes.
Pigmentation
The color of skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred into the keratinocytes via a cellular vesicle called a melanosome (Figure \(\PageIndex{6}\)).
Melanin occurs in two primary forms. Eumelanin exists as black and brown, whereas pheomelanin provides a red color. Dark-skinned individuals produce more melanin than those with pale skin. Exposure to the UV rays of the sun or a tanning salon causes melanin to be manufactured and built up in keratinocytes, as sun exposure stimulates keratinocytes to secrete chemicals that stimulate melanocytes. The accumulation of melanin in keratinocytes results in the darkening of the skin, or a tan. This increased melanin accumulation is protection from UV radiation, which could damage the DNA of epidermal cells and breakdown folic acid, a nutrient necessary for our health and well-being, circulating through the bloodstream in the dermis. In contrast, too much melanin can interfere with the production of vitamin D, an important nutrient involved in calcium absorption, since UV radiation is required for its production. Thus, the amount of melanin present in our skin is dependent on a balance between available sunlight and folic acid destruction, and protection from UV radiation and vitamin D production.
It requires about 10 days after initial sun exposure for melanin synthesis to peak, which is why pale-skinned individuals tend to suffer sunburns of the epidermis initially. Dark-skinned individuals can also get sunburns, but are more protected than are pale-skinned individuals. Melanosomes are temporary structures that are eventually destroyed by fusion with lysosomes; this fact, along with melanin-filled keratinocytes in the stratum corneum sloughing off, makes tanning impermanent.
Too much sun exposure can eventually lead to wrinkling due to the destruction of the cellular structure of the skin, and in severe cases, can cause sufficient DNA damage to result in skin cancer. When there is an irregular accumulation of melanocytes in the skin, freckles appear. Moles are larger masses of melanocytes, and although most are benign, they should be monitored for changes that might indicate the presence of cancer (Figure \(\PageIndex{7}\)).
Carotene, an orange/red pigment found in many vegetables such as carrots, can also have an affect on skin pigmentation. Once consumed, carotene is converted by the human body into vitamin A, which in turn is used for vision, immune system function, and to stimulate fibroblasts in the skin. Recall that fibroblasts produce the elastic and collagen fibers of the dermis, so having active fibroblast helps with the firmness of skin. However, the over intake of carotene can cause the skin to turn yellowish-orange in color, as a result of the excess being stored just under the skin.
Another factor that can affect the appearance of skin is the activity of hemoglobin in the blood stream. Hemoglobin is a pigment found in red blood cells that is responsible for carrying oxygen throughout the body. A sudden drop in oxygenation can affect skin color, causing the skin to initially turn ashen (white). With a prolonged reduction in oxygen levels, dark red deoxyhemoglobin (hemoglobin not carrying oxygen) becomes dominant in the blood, making the skin appear blue, a condition referred to as cyanosis (kyanos is the Greek word for “blue”). This happens when the oxygen supply is restricted, as when someone is experiencing difficulty in breathing because of asthma or a heart attack. However, in these cases the effect on skin color has nothing do with the skin’s pigmentation.
DISORDER OF THE.....
Integumentary System
The first thing a clinician sees is the skin, and so the examination of the skin should be part of any thorough physical examination. Most skin disorders are relatively benign, but a few, including melanomas, can be fatal if untreated. A couple of the more noticeable disorders, albinism and vitiligo, affect the appearance of the skin and its accessory organs. Although neither is fatal, it would be hard to claim that they are benign, at least to the individuals so afflicted.
Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily due to the inability of melanocytes to produce melanin. Individuals with albinism tend to appear white or very pale due to the lack of melanin in their skin and hair. Recall that melanin helps protect the skin from the harmful effects of UV radiation. Individuals with albinism tend to need more protection from UV radiation, as they are more prone to sunburns and skin cancer. They also tend to be more sensitive to light and have vision problems due to the lack of pigmentation on the retinal wall. Treatment of this disorder usually involves addressing the symptoms, such as limiting UV light exposure to the skin and eyes. In vitiligo , the melanocytes in certain areas lose their ability to produce melanin, possibly due to an autoimmune reaction. This leads to a loss of color in patches (Figure \(\PageIndex{8}\)). Neither albinism nor vitiligo directly affects the lifespan of an individual.
Other changes in the appearance of skin coloration can be indicative of diseases associated with other body systems. Liver disease or liver cancer can cause the accumulation of bile and the yellow pigment bilirubin, leading to the skin appearing yellow or jaundiced ( jaune is the French word for “yellow”). Tumors of the pituitary gland can result in the secretion of large amounts of melanocyte-stimulating hormone (MSH), which results in a darkening of the skin. Similarly, Addison’s disease can stimulate the release of excess amounts of adrenocorticotropic hormone (ACTH), which can give the skin a deep bronze color.
Concept Review
The skin is composed of two major layers: a superficial epidermis and a deeper dermis. The epidermis consists of several layers beginning with the innermost (deepest) stratum basale (germinatum), followed by the stratum spinosum, stratum granulosum, stratum lucidum (when present), and ending with the outermost layer, the stratum corneum. The topmost layer, the stratum corneum, consists of dead cells that shed periodically and is progressively replaced by cells formed from the basal layer. The stratum basale also contains melanocytes, cells that produce melanin, the pigment primarily responsible for giving skin its color. Melanin is transferred to keratinocytes in the stratum spinosum to protect from UV rays.
The dermis connects the epidermis to the hypodermis, and provides strength and elasticity due to the presence of collagen and elastic fibers. It has only two layers: the papillary layer composed of loose connective tissue with papillae that extend into the epidermis and the lower, reticular layer composed of dense irregular connective tissue. The hypodermis, deep to the dermis of skin, is the connective tissue that connects the dermis to underlying structures; it also harbors adipose tissue for fat storage and protection.
Review Questions
Q. The papillary layer of the dermis is most closely associated with which layer of the epidermis?
A. stratum spinosum
B. stratum corneum
C. stratum granulosum
D. stratum basale
- Answer
-
Answer: D
Q. Langerhans cells are commonly found in the ________.
A. stratum spinosum
B. stratum corneum
C. stratum granulosum
D. stratum basale
- Answer
-
Answer: A
Q. The papillary and reticular layers of the dermis are composed mainly of ________.
A. melanocytes
B. keratinocytes
C. connective tissue
D. adipose tissue
- Answer
-
Answer: C
Q. Collagen lends ________ to the skin.
A. elasticity
B. structure
C. color
D. UV protection
- Answer
-
Answer: B
Q. Which of the following is not a function of the hypodermis?
A. protects underlying organs
B. helps maintain body temperature
C. source of blood vessels in the epidermis
D. a site to long-term energy storage
- Answer
-
Answer: C
Critical Thinking Questions
Q. What determines the color of skin, and what is the process that darkens skin when it is exposed to UV light?
- Answer
-
A. The pigment melanin, produced by melanocytes, is primarily responsible for skin color. Melanin comes in different shades of brown and black. Individuals with darker skin have darker, more abundant melanin, whereas fair-skinned individuals accumulate less of a lighter shade of melanin. Exposure to UV irradiation stimulates the melanocytes to produce and secrete more melanin.
Q. Cells of the epidermis derive from stem cells of the stratum basale. Describe how the cells change as they become integrated into the different layers of the epidermis.
- Answer
-
A. As the cells move into the stratum spinosum, they begin the synthesis of keratin and extend cell processes, desmosomes, which link the cells. As the stratum basale continues to produce new cells, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. The cells become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin and keratohyalin. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that form the stratum lucidum and the stratum corneum. The keratinocytes in these layers are mostly dead and flattened. Cells in the stratum corneum are periodically shed.
Glossary
- albinism
- genetic disorder that affects the skin, in which there is no melanin production
- basal cell
- type of stem cell found in the stratum basale and in the hair matrix that continually undergoes cell division, producing the keratinocytes of the epidermis
- dermal papilla
- (plural = dermal papillae) extension of the papillary layer of the dermis that increases surface contact between the epidermis and dermis
- dermis
- layer of skin between the epidermis and hypodermis, composed mainly of connective tissue and containing blood vessels, hair follicles, sweat glands, and other structures
- desmosome
- structure that forms an impermeable junction between cells
- elastic fibers
- fibers made of the protein elastin that increase the elasticity of the dermis
- eleiden
- clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss
- epidermis
- outermost tissue layer of the skin
- hypodermis
- connective tissue connecting the integument to the underlying bone and muscle
- integumentary system
- skin and its accessory structures
- keratin
- type of structural protein that gives skin, hair, and nails its hard, water-resistant properties
- keratinocyte
- cell that produces keratin and is the most predominant type of cell found in the epidermis
- keratohyalin
- granulated protein found in the stratum granulosum
- Langerhans cell
- specialized dendritic cell found in the stratum spinosum that functions as a macrophage
- melanin
- pigment that determines the color of hair and skin
- melanocyte
- cell found in the stratum basale of the epidermis that produces the pigment melanin
- melanosome
- intercellular vesicle that transfers melanin from melanocytes into keratinocytes of the epidermis
- Merkel cell
- receptor cell in the stratum basale of the epidermis that responds to the sense of touch
- papillary layer
- superficial layer of the dermis, made of loose, areolar connective tissue
- reticular layer
- deeper layer of the dermis; it has a reticulated appearance due to the presence of abundant collagen and elastin fibers
- stratum basale
- deepest layer of the epidermis, made of epidermal stem cells
- stratum corneum
- most superficial layer of the epidermis
- stratum granulosum
- layer of the epidermis superficial to the stratum spinosum
- stratum lucidum
- layer of the epidermis between the stratum granulosum and stratum corneum, found only in thick skin covering the palms, soles of the feet, and digits
- stratum spinosum
- layer of the epidermis superficial to the stratum basale, characterized by the presence of desmosomes
- vitiligo
- skin condition in which melanocytes in certain areas lose the ability to produce melanin, possibly due an autoimmune reaction that leads to loss of color in patches
Contributors and Attributions
-
OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology


4.6: Parameters and Arguments
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Overview
A parameter is a special kind of variable used in a function to refer to one of the pieces of data provided as input to the function. These pieces of data are the values of the arguments with which the function is going to be called/invoked. An ordered list of parameters is usually included in the definition of a function, so that, each time the function is called, its arguments for that call are evaluated, and the resulting values can be assigned to the corresponding parameters. [1]
Discussion
Recall that the modular programming approach separates the functionality of a program into independent modules. To separate the functionality of one function from another, each function is given its own unique input variables, called parameters. The parameter values, called arguments, are passed to the function when the function is called. Consider the following function pseudocode:
Function CalculateCelsius (Real fahrenheit) Declare Real celsius Assign celsius = (fahrenheit - 32) * 5 / 9 Return Real celsius
If the CalculateCelsius function is called passing in the value 100, as in
CalculateCelsius(100)
, the parameter is
fahrenheit
and the argument is
100
. The terms parameter and argument are often used interchangeably. However, parameter refers to the variable identifier (fahrenheit) while argument refers to the variable value (100).
Functions may have no parameters or multiple parameters. Consider the following function pseudocode:
Function DisplayResult (Real fahrenheit, Real celsius) Output fahrenheit & "° Fahrenheit is " & celsius & "° Celsius" End
If the DisplayResult function is called passing in the values 98.6 and 37.0, as in
DisplayResults(98.6, 37.0)
, the argument or value for the fahrenheit parameter is 98.6 and the argument or value for the celsius parameter is 37.0. Note that the arguments are passed positionally. Calling
DisplayResults(37.0, 98.6)
would result in incorrect output, as the value of fahrenheit would be 37.0 and the value of celsius would be 98.6.
Some programming languages, such as Python, support named parameters. When calling functions using named parameters, parameter names and values are used, and positions are ignored. When names are not used, arguments are identified by position. For example, any of the following function calls would be valid:
CalculateCelsius(98.6, 37.0) CalculateCelsius(fahrenheit=98.6, celsius=37.0) CalculateCelsius(celsius=37.0, fahrenheit=98.6)
Key Terms
- argument
- A value provided as input to a function.
- parameter
- A variable identifier provided as input to a function.


1.2: Physical and Chemical Properties
- Describe the difference between physical and chemical properties or changed.
- Identify a property or transformation as either physical or chemical using symbolic, particulate, or macroscopic representations.
- Identify the properties of matter as extensive or intensive.
The characteristics that enable us to distinguish one substance from another are called properties. A physical property is a characteristic of matter that is not associated with a change in its chemical composition. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity. We can observe some physical properties, such as density and color, without changing the physical state of the matter observed. Other physical properties, such as the melting temperature of iron or the freezing temperature of water, can only be observed as matter undergoes a physical change. A physical change is a change in the state or properties of matter without any accompanying change in its chemical composition (the identities of the substances contained in the matter). We observe a physical change when wax melts, when sugar dissolves in coffee, and when steam condenses into liquid water (Figure \(\PageIndex{1}\)). Other examples of physical changes include magnetizing and demagnetizing metals (as is done with common antitheft security tags) and grinding solids into powders (which can sometimes yield noticeable changes in color). In each of these examples, there is a change in the physical state, form, or properties of the substance, but no change in its chemical composition.
The change of one type of matter into another type (or the inability to change) is a chemical property . Examples of chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion. Iron, for example, combines with oxygen in the presence of water to form rust; chromium does not oxidize (Figure \(\PageIndex{2}\)). Nitroglycerin is very dangerous because it explodes easily; neon poses almost no hazard because it is very unreactive.
To identify a chemical property, we look for a chemical change. A chemical change always produces one or more types of matter that differ from the matter present before the change. The formation of rust is a chemical change because rust is a different kind of matter than the iron, oxygen, and water present before the rust formed. The explosion of nitroglycerin is a chemical change because the gases produced are very different kinds of matter from the original substance. Other examples of chemical changes include reactions that are performed in a lab (such as copper reacting with nitric acid), all forms of combustion (burning), and food being cooked, digested, or rotting (Figure \(\PageIndex{3}\)).
Properties of matter fall into one of two categories. If the property depends on the amount of matter present, it is an extensive property . The mass and volume of a substance are examples of extensive properties; for instance, a gallon of milk has a larger mass and volume than a cup of milk. The value of an extensive property is directly proportional to the amount of matter in question. If the property of a sample of matter does not depend on the amount of matter present, it is an intensive property . Temperature is an example of an intensive property. If the gallon and cup of milk are each at 20 °C (room temperature), when they are combined, the temperature remains at 20 °C. As another example, consider the distinct but related properties of heat and temperature. A drop of hot cooking oil spattered on your arm causes brief, minor discomfort, whereas a pot of hot oil yields severe burns. Both the drop and the pot of oil are at the same temperature (an intensive property), but the pot clearly contains much more heat (extensive property).
While many elements differ dramatically in their chemical and physical properties, some elements have similar properties. We can identify sets of elements that exhibit common behaviors. For example, many elements conduct heat and electricity well, whereas others are poor conductors. These properties can be used to sort the elements into three classes: metals (elements that conduct well), nonmetals (elements that conduct poorly), and metalloids (elements that have properties of both metals and nonmetals).
The periodic table is a table of elements that places elements with similar properties close together (Figure \(\PageIndex{5}\)). You will learn more about the periodic table as you continue your study of chemistry.
Summary
All substances have distinct physical and chemical properties, and may undergo physical or chemical changes. Physical properties, such as hardness and boiling point, and physical changes, such as melting or freezing, do not involve a change in the composition of matter. Chemical properties, such flammability and acidity, and chemical changes, such as rusting, involve production of matter that differs from that present beforehand.
Measurable properties fall into one of two categories. Extensive properties depend on the amount of matter present, for example, the mass of gold. Intensive properties do not depend on the amount of matter present, for example, the density of gold. Heat is an example of an extensive property, and temperature is an example of an intensive property.
Glossary
- chemical change
- change producing a different kind of matter from the original kind of matter
- chemical property
- behavior that is related to the change of one kind of matter into another kind of matter
- extensive property
- property of a substance that depends on the amount of the substance
- intensive property
- property of a substance that is independent of the amount of the substance
- physical change
- change in the state or properties of matter that does not involve a change in its chemical composition
- physical property
- characteristic of matter that is not associated with any change in its chemical composition
Contributors and Attributions
-
Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at<EMAIL_ADDRESS>).


3.9: Vaccine Storage and Handling
Vaccines must be carefully stored and handled from the time of manufacturing to administration. Health professionals need to be cognizant of the harmful impact that excessive heat and cold can have on vaccines, rendering them ineffective or destroyed. Errors in storage or handling also contribute to vaccine wastage . Consult the product monograph or local public health authority for information on proper storage conditions for each vaccine, including temperature. As a health professional, it is important to review the policies and procedures developed by the Public Health Agency of Canada (PHAC) (2015) and your provincial/territorial Ministry of Health and Local Public Health organization.
PHAC (2015) outlines a set of procedures to follow when handling and storing vaccines. These procedures include but are not limited to:
- Each office/location should have an identified staff member who is the primary vaccine coordinator and another member as a backup. Both should be fully trained in vaccine storage and handling protocols.
- Always refer to the vaccine product monograph for the most current information about storage information.
- Refrigerators and freezers, used for vaccine storage, must be dedicated to the storage of vaccines only . They should be placed in an area that is not accessible to the public.
- Refrigerators and freezer units must have a calibrated temperature monitoring device that provides continuous recording or minimum/maximum temperatures that are properly monitored, i.e. checked and documented twice a day .
- The majority of vaccines should be stored in a refrigerator at temperatures of +2 to +8 degrees Celsius . Some vaccines must be kept in a freezer at temperatures of -15 degrees Celsius or lower. Doors of units should be kept closed and opened a limited number of times.
- Units should have a sign that says: “Do not adjust refrigerator or freezer temperature controls. Notify primary vaccine coordinator or the backup/delegate coordinator if adjustments are necessary.”
- Vaccines should be placed in labelled, mesh baskets and stored in the middle of the unit rather than in doors or drawers. Stock should be rotated so that vaccines with approaching expiry dates are positioned at the front and used first.
- Vaccines are stored in their original packaging.
- Some vaccines are light sensitive and health professionals should refer to the product information of each vaccine to determine restrictions.
Each site must have a contingency plan in place for vaccine storage in the event of electricity disruptions or unit malfunctions. If procedures have not been adhered to, and/or the temperature decreases in the required unit, notify the primary vaccine coordinator at your site and the local public health unit.
An interactive or media element has been excluded from this version of the text. You can view it online here:
https://ecampusontario.pressbooks.pub/immunizations/?p=127


1.4: Safety, Security, Privacy, and the Ethical Use of Technology
By the end of this section, you will be able to:
- Describe the importance of practicing responsible computer safety and security
- Identify common computer security issues
- List measures to prevent computer security breaches
- Describe the importance of privacy in a digital world
At WorldCorp, you’ve realized how the evolution of computing has led to your present-day status as a new employee. You’re getting the hang of how computers are put together, how they have changed the business landscape, and how you need to understand their basic components to thrive in your industry. Another part of that understanding is learning how to safely navigate the computer world, both in the company’s internal systems and in external systems on the internet and the World Wide Web.
The Importance of Computer Safety and Security
The protection of computer systems and information that prevents unauthorized use is referred to as computer security . Computer ethics are guidelines for the morally acceptable use of computers in society. Any criminal offense that involves a computer and a network is referred to as cybercrime . One of the most common types of cybercrimes is identity theft , which occurs when an unauthorized user steals an individual’s personal information, such as a Social Security number or credit card information for economic gain. An increase in the number of hackers —individuals who gain unauthorized access to computer systems in an attempt to steal someone’s information—has prompted the development of software programs designed to protect consumers’ identities, such as LifeLock .
There are strategies you can employ that will keep your computer, and the information you have saved on it, safe and secure from theft and hacking. These include:
- using security suites that can protect user privacy and security while on the internet
- using a firewall , which is a barrier between a network that is secured and one that is not secured, to provide additional security
- setting up password-protected network access
- avoiding logging in to accounts on an open network (one that is not password protected)
- using encryption to make it impossible for unauthorized individuals to gain access
Data and Identity Theft
In addition to hackers who target individual users, corporate espionage (also known as industrial, economic, or corporate spying) is conducted for commercial or financial gain by targeting businesses, government agencies, energy companies, and even schools. Corporate espionage can take the form of unethical or illegal acquisition of intellectual property (such as customer data, pricing, or research and development information) or trade secrets through theft, bribery, or blackmail. Examples of corporate espionage include:
- trespassing on a competitor’s property and/or gaining unauthorized access to files
- wiretapping —the secret interception of electronic communications
- domain hacking , which occurs when another entity steals the original party’s domain name
- phishing to lure competitors’ employees to open emails, thereby exposing information
Attempts to get users to interact with an email or website that appears to be legitimate but is actually fake is called phishing . Phishing lures users to provide their personal information and login credentials through these hoax sites and emails. This is usually through the use of spoofing . Spoofing is communication (usually an email) that on the surface looks to be legitimate from a trusted source. These emails have become much more sophisticated and are designed to look more and more like real correspondence from a company or even a government agency such as the IRS. Something that has grown increasingly common is ransomware , malicious software that encrypts computer data, rendering it useless and inaccessible, and forcing the owner to pay a ransom to regain access. Software that is designed with the purpose of damaging a user’s computer system once it has access to that system is called malware .
Password Management and Biometrics
For all of these threats to online security, there are protective steps you can take. A set of principles and best practices for storing and managing passwords in a manner that is likely to prevent unauthorized access is called password management . You may password protect your computer, as well as various accounts you may access through your computer and the internet. Having a strong password will ensure that hackers cannot figure out your password easily. Many organizations today use multifactor authentication to provide an additional layer of security. For example, when accessing your bank account on your phone or your laptop, you may be asked to enter a specific code that is sent via email or text. This now provides two layers of security—first, entering the correct password, then correctly entering the code that was sent to you. Multifactor authentication can also be used by businesses when accessing the company software or computer network.
Some tips for creating a strong password include:
- Avoid using a real name (either your own or the company’s) as your password.
- Use a combination of letters and numbers with at least eight characters.
- Do not use a complete word such as “password.”
- Do not reuse passwords.
- Use a combination of uppercase and lowercase letters.
- Incorporate special symbols instead of letters or numbers (such as an exclamation point or dollar sign instead of a numeral).
In addition to passwords, you can also use biometrics to protect your computer and information. Unique physical markers of an individual that can be used to restrict access to only those who match these physical characteristics, such as retinal scans and fingerprints, are called biometrics . Biometrics are much harder to hack as they cannot be guessed or stolen.
Internet and Web Privacy
The internet is pervasive and omnipresent. It is part of all you do in business and in your everyday life. How people conduct themselves online, what they share, and what they visit—all this information is captured and saved in various places, from internet providers’ servers to browser companies such as Google to different social media sites. This information is captured and saved even if deleted from your computer or account. It is important to consider how to represent yourself and what to share to maintain your privacy.
Cookies
After you have searched for a product on the internet, do you notice that you suddenly start receiving advertisements for that product, or that a store website now displays that product on its front page? For that, you can thank cookies. Small data files that are deposited on user hard disks from websites you visit are called cookies . They keep track of your browsing and search history, collecting information about your potential interests to tailor advertisements and product placement on websites. These cookies can be either blocked or accepted, depending on a company’s privacy policy. The potential risk of cookies is that they can store information about the user, user preferences, and user browsing habits. That said, they can also save time by storing users’ login information and browsing preferences, allowing internet pages to load faster than if you had loaded them the first time. Regardless of convenience, it is a good idea to clear cookies from time to time and to restrict cookies on certain sites depending on your own preferences.
Browsing History
Your browsing history includes all websites you may have visited, as well as any actions you may have taken on those websites. It is typically saved locally on your computer within the browser application, as well as with the company that provides the browser. Your internet or data provider may also keep track of your browsing history. While this information is handy to have for future reference, consider clearing your browsing history from your personal computer on a regular basis. Be aware that your employer may also collect this information; while using a work computer, you should avoid visiting websites that do not support your work function. Both Google analytics and your company can theoretically store browsing data for a long time, even after you delete it.
Temporary Files
As the name implies, temporary files are created by a program to allow it to complete a task or tasks. These files are handy to have in case of a sudden shutdown, as they may help to recover a file that might otherwise be lost. Many temporary files are automatically deleted once the task is complete or the file is saved permanently. But others may stick around; these files are saved in your temp folder. On a Windows computer, you can access your temp folder by typing %temp% in the Windows search bar at the bottom left of your screen.
On a Mac, open the Finder and select Go ≫ Go to Folder. In the search bar, type ~/Library/Caches/ and then click Go to run the command. A window will open with a list of all the generated temp files saved on your Mac. You can easily select and delete these files.
Posting on Social Media
According to Pew Research, “seven-in-ten Americans use social media to connect with one another, engage with news content, share information and entertain themselves.” Some of the most popular platforms today are TikTok , Facebook , YouTube , Instagram , and WhatsApp . Figure 1.31 shows the sites adults in the United States use most. The United States and China have the most social media users of all countries worldwide. Social media has exploded in popularity and is used widely for both personal and business purposes. Businesses and individuals must be mindful of what they post on social media. Even the most private accounts can have data breaches, allowing others to save and/or share private content. It is important to consider what you post, as well as any potential unintended consequences that might arise from social media use. You must also be aware of spoof accounts that present as a reputable person, when in fact they are attempting to con or mislead an individual. Similarly, AI and bots may interact with users, posing as real people when in fact they are nothing more than a computer algorithm.
Ultimately, you should be sure to present a positive self-image on the internet, particularly on networking social media platforms such as LinkedIn . When considering how you want to represent yourself online, answer these questions: (1) Is this information accurate? (2) Will this post be potentially detrimental to my schooling and/or career? (3) Is the information hurtful or detrimental to someone else?
Ensuring Privacy
Privacy involves practices related to the collection and use of data about an individual. Many companies will have privacy policies when you sign up as a customer or purveyor of their content. It is important to read these policies to ensure you are not inadvertently providing permission to use your data and information in a way that you do not actually approve of. In addition, many companies will disclose they sell your information to other companies seeking similar customers. It is important to decline these permissions to avoid circulation of your contact information.
Minimal Data Collection from Customers
Collecting data from customers allows organizations to determine their needs and identify niche markets. Companies must ensure they are collecting the most minimal amount of data necessary from their customers to achieve these goals. Collecting too much data places both the company and the customer at risk. The company is responsible for ensuring that information is used responsibly and within the parameters of its privacy agreement; any data breach puts the company at risk of liability. Similarly, customers have the right to know how their information is used by the company and may request compensation if it is used inappropriately. Therefore, companies must ensure that they collect only the most minimal amount of data required to meet their business needs.
Data Security
Data security involves protecting digital information (data) from being accessed or used by parties who should not have access, or for purposes it should not be used for. Just as individuals must ensure they protect their information from hackers and malicious intent, companies are responsible for ensuring they use the most up-to-date data security measures to protect both customer information and proprietary company information and data.
Companies must ensure both internal and external security. Internally, a company should establish policies and protocols to ensure employees are abiding by data security measures. A company should also limit employee access to certain information. Keeping technologies up to date, with the most current security software, is also important. Depending on the size of the company, it may be worthwhile to establish a cybersecurity branch that employs qualified professionals dedicated to data security.
There are a number of strategies a company can use to keep data secure. Encrypting the data will render information unreadable to unauthorized users. Without the access key, encrypted information presents as nothing more than a meaningless string of characters. Companies, like individuals, can also take steps to delete files, software, and data that is no longer of use. And they can take it a step further by practicing data erasure , wherein the information is not only deleted but overwritten as well. In another approach, data masking , personally identifiable information is removed from the data, allowing the company to make decisions about its customers without associating the data with an individual’s personal information. By taking these steps, companies ensure they can recover from a data breach quickly, reinforcing their data resiliency .


2 .
How do preexisting nutritional deficiencies impact pregnancy outcomes and obstetric management?
3 .
What is the association between special populations, pregnancy outcomes, and obstetric management?
4 .
How do preexisting medical conditions impact pregnancy outcomes and obstetric management?
5 .
Identify and describe two conditions limited to pregnancy that may cause abdominal pain and vaginal bleeding in the first trimester. What are the key differences in their pathophysiology, and how would the management approach differ?
6 .
Discuss the diagnostic tools that can be utilized to investigate conditions limited to pregnancy, such as those causing abdominal pain and bleeding. How do these tools contribute to the understanding of the pathophysiology, and how might they guide management decisions?
7 .
As pregnancy progresses into the second trimester, what conditions become more relevant, and how might the management strategies differ from those in the first trimester?
8 .
Discuss the key considerations for managing conditions in the second and third trimesters. How does the focus of care shift, and what interventions might be initiated to address potential complications?


13.1: Classification of Cancers
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Cancers can be classified based on the tissues in which they originate. Sarcomas are cancers that originate in mesoderm tissues, such as bone or muscle, and cancers arising in glandular tissues (e.g. breast, prostate) are classified as adenocarcinomas . Carcinomas originate in epithelial cells (both inside the body and on its surface) and are the most common types of cancer (~85%). Each of these classifications may be further sub-‐divided. For example, squamous cell carcinoma (SCC) , basal cell carcinoma (BCC) , and melanoma are all types of skin cancers originating respectively in the squamous cells, basal cells, or melanocytes of the skin.


16.3: Scientific Notation (Appendix C)
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In astronomy (and other sciences), it is often necessary to deal with very large or very small numbers. In fact, when numbers become truly large in everyday life, such as the national debt in the United States, we call them astronomical. Among the ideas astronomers must routinely deal with is that the Earth is 150,000,000,000 meters from the Sun, and the mass of the hydrogen atom is 0.00000000000000000000000000167 kilograms. No one in his or her right mind would want to continue writing so many zeros!
Instead, scientists have agreed on a kind of shorthand notation, which is not only easier to write, but (as we shall see) makes multiplication and division of large and small numbers much less difficult. If you have never used this powers-of-ten notation or scientific notation, it may take a bit of time to get used to it, but you will soon find it much easier than keeping track of all those zeros.
Writing Large Numbers
In scientific notation, we generally agree to have only one number to the left of the decimal point. If a number is not in this format, it must be changed. The number 6 is already in the right format, because for integers, we understand there to be a decimal point to the right of them. So 6 is really 6., and there is indeed only one number to the left of the decimal point. But the number 965 (which is 965.) has three numbers to the left of the decimal point, and is thus ripe for conversion.
To change 965 to proper form, we must make it 9.65 and then keep track of the change we have made. (Think of the number as a weekly salary and suddenly it makes a lot of difference whether we have $965 or $9.65.) We keep track of the number of places we moved the decimal point by expressing it as a power of ten. So 965 becomes 9.65 × 10 2 or 9.65 multiplied by ten to the second power. The small raised 2 is called an exponent, and it tells us how many times we moved the decimal point to the left.
Note that 10 2 also designates 10 squared, or 10 × 10, which equals 100. And 9.65 × 100 is just 965, the number we started with. Another way to look at scientific notation is that we separate out the messy numbers out front, and leave the smooth units of ten for the exponent to denote. So a number like 1,372,568 becomes 1.372568 times a million (10 6 ) or 1.372568 times 10 multiplied by itself 6 times. We had to move the decimal point six places to the left (from its place after the 8) to get the number into the form where there is only one digit to the left of the decimal point.
The reason we call this powers-of-ten notation is that our counting system is based on increases of ten; each place in our numbering system is ten times greater than the place to the right of it. As you have probably learned, this got started because human beings have ten fingers and we started counting with them. (It is interesting to speculate that if we ever meet intelligent life-forms with only eight fingers, their counting system would probably be a powers-of-eight notation!)
So, in the example we started with, the number of meters from Earth to the Sun is 1.5 × 10 11 . Elsewhere in the book, we mention that a string 1 light-year long would fit around Earth’s equator 236 million or 236,000,000 times. In scientific notation, this would become 2.36 × 10 8 . Now if you like expressing things in millions, as the annual reports of successful companies do, you might like to write this number as 236 × 10 6 . However, the usual convention is to have only one number to the left of the decimal point.
Writing Small Numbers
Now take a number like 0.00347, which is also not in the standard (agreed-to) form for scientific notation. To put it into that format, we must make the first part of it 3.47 by moving the decimal point three places to the right . Note that this motion to the right is the opposite of the motion to the left that we discussed above. To keep track, we call this change negative and put a minus sign in the exponent. Thus 0.00347 becomes 3.47 × 10 −3 .
In the example we gave at the beginning, the mass of the hydrogen atom would then be written as 1.67 × 10 −27 kg. In this system, one is written as 10 0 , a tenth as 10 −1 , a hundredth as 10 −2 , and so on. Note that any number, no matter how large or how small, can be expressed in scientific notation.
Multiplication and Division
Scientific notation is not only compact and convenient, it also simplifies arithmetic. To multiply two numbers expressed as powers of ten, you need only multiply the numbers out front and then add the exponents. If there are no numbers out front, as in 100 × 100,000, then you just add the exponents (in our notation, 10 2 × 10 5 = 10 7 ). When there are numbers out front, you have to multiply them, but they are much easier to deal with than numbers with many zeros in them.
Here’s an example:
\[\left( 3 \times 10^5 \right) \times \left( 2 \times 10^9 \right) = 6 \times 10^{14} \nonumber\]
And here’s another example:
\[ \begin{aligned} 0.04 \times 6,000,000 & =\left( 4 \times 10^{−2} \right) \times \left( 6 \times 10^6 \right) \\ & = 24×10^4 \\ & = 2.4×10^5 \end{aligned} \nonumber\]
Note in the second example that when we added the exponents, we treated negative exponents as we do in regular arithmetic (−2 plus 6 equals 4). Also, notice that our first result had a 24 in it, which was not in the acceptable form, having two places to the left of the decimal point, and we therefore changed it to 2.4 and changed the exponent accordingly.
To divide, you divide the numbers out front and subtract the exponents. Here are several examples:
\[ \begin{array}{l} \frac{1,000,000}{1000} = \frac{10^6}{10^3} = 10^{(6-3)} = 10^3 \\ \frac{9 \times 10^{12}}{2 \times 10^3} = 4.5 \times 10^9 \\ \frac{2.8 \times 10^2}{6.2 \times 10^5} =4.52 \times 10^{−4} \end{array} \nonumber\]
In the last example, our first result was not in the standard form, so we had to change 0.452 into 4.52, and change the exponent accordingly.
If this is the first time that you have met scientific notation, we urge you to practice many examples using it. You might start by solving the exercises below. Like any new language, the notation looks complicated at first but gets easier as you practice it.
Exercises
- At the end of September, 2015, the New Horizons spacecraft (which encountered Pluto for the first time in July 2015) was 4.898 billion km from Earth. Convert this number to scientific notation. How many astronomical units is this? (An astronomical unit is the distance from Earth to the Sun, or about 150 million km.)
- During the first six years of its operation, the Hubble Space Telescope circled Earth 37,000 times, for a total of 1,280,000,000 km. Use scientific notation to find the number of km in one orbit.
- In a large university cafeteria, a soybean-vegetable burger is offered as an alternative to regular hamburgers. If 889,875 burgers were eaten during the course of a school year, and 997 of them were veggie-burgers, what fraction and what percent of the burgers does this represent?
- In a 2012 Kelton Research poll, 36 percent of adult Americans thought that alien beings have actually landed on Earth. The number of adults in the United States in 2012 was about 222,000,000. Use scientific notation to determine how many adults believe aliens have visited Earth.
- In the school year 2009–2010, American colleges and universities awarded 2,354,678 degrees. Among these were 48,069 PhD degrees. What fraction of the degrees were PhDs? Express this number as a percent. (Now go and find a job for all those PhDs!)
- A star 60 light-years away has been found to have a large planet orbiting it. Your uncle wants to know the distance to this planet in old-fashioned miles. Assume light travels 186,000 miles per second, and there are 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, and 365 days in a year. How many miles away is that star?
Answers
- 4.898 billion is 4.898 × 10 9 km. One astronomical unit (AU) is 150 million km = 1.5 × 10 8 km. Dividing the first number by the second, we get 3.27 × 10 (9 – 8) = 3.27 × 10 1 AU.
- \(\frac{1.28 \times 10^9 \text{ km}}{3.7 \times 10^4 \text{ orbits}} = 0.346 \times 10^{(9−4)} = 0.346 \times 10^5 = 3.46 \times 10^4 \text{ km per orbit}\).
- \(\frac{9.97 \times 10^2 \text{ veggie burgers}}{8.90 \times 10^5 \text{ total burgers}} = 1.12 \times 10^{(2−5)} = 1.12 \times 10^{(2−5)} = 1.12 \times 10^{−3}\) (or roughly about one thousandth) of the burgers were vegetarian. Percent means per hundred. So \(\frac{1.12 \times 10^{−3}}{10^{−2}} = 1.12 \times 10^{(−3−(−2))} = 1.12 \times 10^{−1} \text{ percent}\) (which is roughly one tenth of one percent).
- 36% is 36 hundredths or 0.36 or 3.6 × 10 −1 . Multiply that by 2.22 × 10 8 and you get about 7.99 × 10 (−1 + 8) = 7.99 × 10 7 or almost 80 million people who believe that aliens have landed on our planet. We need more astronomy courses to educate all those people.
- \(\frac{4.81 \times 10^4}{2.35 \times 10^6} = 2.05 \times 10^{(4−6)} = 2.05 \times 10^{−2} = \text{ about} 2 \%\). (Note that in these examples we are rounding off some of the numbers so that we don’t have more than 2 places after the decimal point.)
- One light-year is the distance that light travels in one year. (Usually, we use metric units and not the old British system that the United States is still using, but we are going to humor your uncle and stick with miles.) If light travels 186,000 miles every second, then it will travel 60 times that in a minute, and 60 times that in an hour, and 24 times that in a day, and 365 times that in a year. So we have 1.86 × 10 5 × 6.0 × 10 1 × 6.0 × 10 1 × 2.4 × 10 1 × 3.65 × 10 2 . So we multiply all the numbers out front together and add all the exponents. We get 586.57 × 10 10 = 5.86 × 10 12 miles in a light year (which is roughly 6 trillion miles—a heck of a lot of miles). So if the star is 60 light-years away, its distance in miles is 6 × 10 1 × 5.86 × 10 12 = 35.16 × 10 13 = 3.516 × 10 14 miles.


2.3: Major Ethical Systems
When learning how to resolve ethical dilemmas , it is important to be able to articulate a justifiable rationale for why we believe one decision seems right and another seems wrong. Having a basic understanding of the major ethical theories will help us toward an ethical resolution learning how to articulate and justify the decision.
At times, some of the ethical theories may seem overly philosophical for our purposes; we may even wonder why we should study theories that were sometimes developed centuries ago when we are primarily dealing with present-day issues. In other instances, some of the ethical theories may seem overbearing. The theories we look at here, however, are important to help us understand why the decisions we make, or someone else makes, are ethical or unethical.
For example, a decision may be made that appears on the surface to be unethical, but when we are aware of the philosophical system used in the decision making, we can then understand the root of the decision and, at the very least, see its intended morality. This allows us to view ethical issues from different perspectives and assists us in making informed decisions.
This book is concerned primarily with normative ethics and understanding only the common normative ethical theories. By dissecting the normative theories of ethics, we can have a clear understanding on the moral decisions we ought to make, or the reason some people make the decisions they do. Ethical theories will be examined only briefly as the focus of this book is contemporary ethical issues facing law enforcement. The descriptions of the following ethical theories are very basic and address only the points required for a basic understanding in a law enforcement context. Examples of how a theory may relate to and assist law enforcement are included.
Overview of Ethical Theories
There are three categories of ethical theories:
- Normative ethics
- Meta ethics
- Applied ethics
Normative theories tell us not only what we ought to do, but also why we do things that in some instances may appear counterintuitive to what we think an ethical decision would be. Such theories are often called ethical systems because they provide a system that allows people to determine ethical actions that individuals should take (Pollock, 2007). Evans and Macmillan (2014, p.27) define normative ethics as “theories of ethics that are concerned with the norms, standards or criteria that define principles of ethical behaviour.” The most common examples of normative ethical theories are utilitarianism, Kantian duty-based ethics (deontology), and divine command theory, which are described later in this chapter. These systems are used by individuals to make decisions when confronted with ethical dilemmas.
Meta-ethics does not address how we ought to behave; rather, meta-ethics is related more to the study of ethical theory itself. Here the interest is in evaluating moral and ethical theories and systems. For example, moral relativism is a meta-ethical theory because it interprets discussions around ethics; a question asked within moral relativism is “is ethics culturally relative?” Evans and Macmillan (2014, p.27) define meta-ethics as “theories of ethics concerned with the moral concepts, theories, and the meaning of moral language. Pollock (2007, p.6) further defines meta-ethics as “a discipline that investigates the meaning of ethical systems and whether they are relative or are universal, and are self-constructed or are independent of human creation.”
For the purposes of this book, meta-ethics will relate to the way we look at and understand normative ethical theories. More concisely, meta-ethics concerns an interpretation and evaluation of the language used within normative ethical theories.
Applied ethics describes how we apply normative theories to specific issues, usually related to work or belonging to an organization; for example, policies and procedures of organizations or ethical codes of outlaw bikers versus ethical codes of police officers. Evans and Macmillan (2014, p.27) define applied ethics as “theories of ethics concerned with the application of normative ethics to particular ethical issues.” An example is knowing and practising the code of ethics for BC Corrections as an employee of BC Corrections or following the British Columbia Police Code of Ethics as a police officer.
With the overview of the three categories of ethical theories we will further analyze each ethical theory or system.
The normative ethical theories that are briefly covered in this chapter are:
- Utilitarianism
- Deontology
- Virtue ethics
- Ethics of care
- Egoism
- Religion or divine command theory
- Natural Law
- Social contract theory
- Rawls’s theory of justice
- Moral relativism


17.1: Introduction to Gauss's Law
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Flux is a general and broadly applicable concept in physics. However, in this chapter, we concentrate on the flux of the electric field. This allows us to introduce Gauss’s law, which is particularly useful for finding the electric fields of charge distributions exhibiting spatial symmetry. The main topics discussed here are
So far, we have found that the electrostatic field begins and ends at point charges and that the field of a point charge varies inversely with the square of the distance from that charge. These characteristics of the electrostatic field lead to an important mathematical relationship known as Gauss’s law. This law is named in honor of the extraordinary German mathematician and scientist Karl Friedrich Gauss (Figure \(\PageIndex{2}\)). Gauss’s law gives us an elegantly simple way of finding the electric field, and, as you will see, it can be much easier to use than the integration method described in the previous chapter. However, there is a catch—Gauss’s law has a limitation in that, while always true, it can be readily applied only for charge distributions with certain symmetries.


5: What is a Family?
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Learning Objectives
It is often said that humans are social creatures. We make friends, live in communities, and connect to acquaintances through shared interests. In recent times, social media has become a new way for people to connect with childhood peers, friends of friends, and even strangers. Perhaps nothing is more central to the social world than the concept of family. Our families represent our earliest relationships and—often—our most enduring ones. In this module, you will learn about the psychology of families. Our discussion will begin with a basic definition of family and how this has changed across time and place. Next, we move on to a discussion of family roles and how families evolve across the lifespan. Finally, we conclude with issues such as divorce and abuse that are important factors in the psychological health of families.


37.3: Interpreting Inequalities
Lesson
Let's examine what inequalities can tell us.
Exercise \(\PageIndex{1}\): True or False: Fractions and Decimals
Is each equation true or false? Be prepared to explain your reasoning.
- \(3(12+5)=(3\cdot 12)\cdot (3\cdot 5)\)
- \(\frac{1}{3}\cdot\frac{3}{4}=\frac{3}{4}\cdot\frac{2}{6}\)
- \(2\cdot (1.5)\cdot 12=4\cdot (0.75)\cdot 6\)
Exercise \(\PageIndex{2}\): Basketball Game
Noah scored \(n\) points in a basketball game.
- What does \(15<n\) mean in the context of the basketball game?
- What does \(n<25\) mean in the context of the basketball game?
- Draw two number lines to represent the solutions to the two inequalities.
- Name a possible value for \(n\) that is a solution to both inequalities.
- Name a possible value for \(n\) that is a solution to \(15<n\), but not a solution to \(n<25\).
- Can -8 be a solution to \(n\) in this context? Explain your reasoning.
Exercise \(\PageIndex{3}\): Unbalanced Hangers
- Here is a diagram of an unbalanced hanger.
- Jada says that the weight of one circle is greater than the weight of one pentagon. Write an inequality to represent her statement. Let \(p\) be the weight of one pentagon and \(c\) be the weight of one circle.
- A circle weighs 12 ounces. Use this information to write another inequality to represent the relationship of the weights. Then, describe what this inequality means in this context.
- Here is another diagram of an unbalanced hanger.
- Write an inequality to represent the relationship of the weights. Let \(p\) be the weight of one pentagon and \(s\) be the weight of one square.
- One pentagon weighs 8 ounces. Use this information to write another inequality to represent the relationship of the weights. Then, describe what this inequality means in this context.
- Graph the solutions to this inequality on a number line.
- Based on your work so far, can you tell the relationship between the weight of a square and the weight of a circle? If so, write an inequality to represent that relationship. If not, explain your reasoning.
- This is another diagram of an unbalanced hanger.
Andre writes the following inequality: \(c+p<s\). Do you agree with his inequality? Explain your reasoning.
- Jada looks at another diagram of an unbalanced hangar and writes: \(s+c>2t\), where \(t\) represents the weight of one triangle. Draw a sketch of the diagram.
Are you ready for more?
Here is a picture of a balanced hanger. It shows that the total weight of the three triangles is the same as the total weight of the four squares.
- What does this tell you about the weight of one square when compared to one triangle? Explain how you know.
- Write an equation or an inequality to describe the relationship between the weight of a square and that of a triangle. Let \(s\) be the weight of a square and \(t\) be the weight of a triangle.
Summary
When we find the solutions to an inequality, we should think about its context carefully. A number may be a solution to an inequality outside of a context, but may not make sense when considered in context.
- Suppose a basketball player scored more than 11 points in a game, and we represent the number of points she scored, \(s\), with the inequality \(s>11\). By looking only at \(s>11\), we can say that numbers such as \(12, 14\frac{1}{2},\) and \(130.25\) are all solutions to the inequality because they each make the inequality true.
\(12>11\qquad 14\frac{1}{2}>11\qquad 130.25>11\)
In a basketball game, however, it is only possible to score a whole number of points, so fractional and decimal scores are not possible. It is also highly unlikely that one person would score more than 130 points in a single game.
In other words, the context of an inequality may limit its solutions.
Here is another example:
- The solutions to \(r<30\) can include numbers such as \(27\frac{3}{4}, 18.5, 0,\) and \(-7\). But if \(r\) represents the number of minutes of rain yesterday (and it did rain), then our solutions are limited to positive numbers. Zero or negative number of minutes would not make sense in this context.
To show the upper and lower boundaries, we can write two inequalities:
\(0<r\qquad r<30\)
Inequalities can also represent comparison of two unknown numbers.
- Let’s say we knew that a puppy weighs more than a kitten, but we did not know the weight of either animal. We can represent the weight of the puppy, in pounds, with \(p\) and the weight of the kitten, in pounds, with \(k\), and write this inequality: \(p>k\)
Glossary Entries
Definition: Solution to an Inequality
A solution to an inequality is a number that can be used in place of the variable to make the inequality true.
For example, 5 is a solution to the inequality \(c<10\), because it is true that \(5<10\). Some other solutions to this inequality are 9.9, 0, and -4.
Practice
Exercise \(\PageIndex{4}\)
There is a closed carton of eggs in Mai's refrigerator. The carton contains \(e\) eggs and it can hold 12 eggs.
- What does the inequality \(e<12\) mean in this context?
- What does the inequality \(e>0\) mean in this context?
- What are some possible values of \(e\) that will make both \(e<12\) and \(e>0\) true?
Exercise \(\PageIndex{5}\)
Here is a diagram of an unbalanced hanger.
- Write an inequality to represent the relationship of the weights. Use \(s\) to represent the weight of the square in grams and \(c\) to represent the weight of the circle in grams.
- One red circle weighs 12 grams. Write an inequality to represent the weight of one blue square.
- Could 0 be a value of \(s\)? Explain your reasoning.
Exercise \(\PageIndex{6}\)
- Jada is taller than Diego. Diego is 54 inches tall (4 feet, 6 inches). Write an inequality that compares Jada’s height in inches, \(j\), to Diego’s height.
- Jada is shorter than Elena. Elena is 5 feet tall. Write an inequality that compares Jada’s height in inches, \(j\), to Elena’s height.
(From Unit 7.2.1)
Exercise \(\PageIndex{7}\)
Tyler has more than $10. Elena has more money than Tyler. Mai has more money than Elena. Let \(t\) be the amount of money that Tyler has, let \(e\) be the amount of money that Elena has, and let \(m\) be the amount of money that Mai has. Select all statements that are true:
- \(t<j\)
- \(m>10\)
- \(e>10\)
- \(t>10\)
- \(e>m\)
- \(t<e\)
Exercise \(\PageIndex{8}\)
Which is greater, \(\frac{-9}{20}\) or \(-0.5\)? Explain how you know. If you get stuck, consider plotting the numbers on a number line.
(From Unit 7.1.3)
Exercise \(\PageIndex{9}\)
Select all the expressions that are equivalent to \(\left(\frac{1}{2}\right)^{3}\).
- \(\frac{1}{2}\cdot\frac{1}{2}\cdot\frac{1}{2}\)
- \(\frac{1}{2^{3}}\)
- \(\left(\frac{1}{3}\right)^{2}\)
- \(\frac{1}{6}\)
- \(\frac{1}{8}\)
(From Unit 6.3.2)