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.
Definition of compound. 1  transitive verb. 2  1 : to put together (parts) so as to form a whole : combine compound ingredients â¦ a thick sauce compounded of chilies, garlic, and ginger. 3  2 : to form by combining parts compound a medicine.