Durham tubes are inverted (top of tube facing the bottom of the test tube) such that the tubes are closed at the top and open at the bottom. When gas is produced in these media a. small bubble representing trapped gas. can be found in the tube.
A compound is a substance formed when two or more chemical elements are chemically bonded together. Two types of chemical bonds common in compounds are covalent bonds and ionic bonds.The elements in any compound are always present in fixed ratios.xample 1: Pure water is a compound made from two elements-hydrogen and oxygen. The ratio of hydrogen to oxygen in water is always 2:1. Each molecule of water contains two hydrogen atoms bonded to a single oxygen atom. Example 2: Pure table salt is a compound made from two elements-sodium and chlorine.
Noun. 1. chemical science-the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions. chemistry. electronegativity, negativity - (chemistry) the tendency of an atom or radical to attract electrons in the formation of an ionic bond.