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.
An element is any substance that consists of only one type of atom, that is all atoms have the same number of protons. A compound is a substance that has two or more element â¦ s chemically bonded together either covalently or ionically in a fixed ratio.n element is a pure substance composed of 1 type of atom. Meaning all the atoms have the same number of protons. A compound is a pure substance composed of 2 or more types â¦ of atom chemically bonded together.