LISTENING A CHEMISTRY LESSON 1 2.6 You are going to listen to a lesson in which a Chemistry teacher revises the main ideas about chemical substances. While listening, fill in the blanks in the passage using the words in the box. atoms (2) bases change compounds electrons (2) elements formula inorganic liquid matter metals metalloids mixtures molecule negative neutrons no non-metals (2) nucleus organic oxygen positive protons salts solutions suspensions symbol water Chemistry deals with (1) .................................... It studies the composition of substances, their action and the chemical changes they undergo. Matter is made up of pure substances called (2) ..................................., which are identified by a name and represented by a chemical (3) ................................... consisting of one or two letters. Elements are divided into (4) ................................... (which are good conductors of electricity), (5) ................................... (which are poor conductors of ACTIVITIES electricity), and (6) .................................... Chemical elements are made up of (7) .................................... An atom is the smallest particle into which an element can be subdivided without losing its characteristic properties. The atom, too, is divisible into smaller particles: (8) ..................................., (9) ................................... and (10) .................................... The atom is divided into two regions: the (11) ..................................., or centre, in which the protons and neutrons are located, and a surrounding orbit or cloud or shell , in which the (12) ................................... move continuously. Protons and electrons carry one unit of (13) ................................... and (14) ................................... electrical charge respectively, while the neutron carries (15) ................................... charge. When two or more atoms are bonded together by electron sharing, they form a (16) ................................... Chemical (17) ................................... are made up of atoms of different elements combined. Their properties are often different from those of the elements that make them up. In fact, a chemical (18) ................................... takes place when atoms of different elements combine to form a molecule. For example, two gases combined may form a (19) .................................... Compounds may be (20) ................................... or (21) .................................... Inorganic compounds are divided into five groups: oxides which are combinations of (22) ................................... with metals; anhydrides which are combinations of oxygen with (23) ...................................; acids which are combinations of an anhydride with (24) ...................................; (25) ................................... which are combinations of oxides with water; and (26) ................................... which are combinations of a metal with a non-metal. A chemical (27) ................................... represents a molecule of an element or of a compound. It is made up of one or more symbols for the element or elements present in the molecule and subscripts showing the number of (28) ................................... of each element present in the molecule. Liquid or solid substances dissolved into other substances form (29) .................................... Substances distributed but not dissolved into other substances form (30) ................................... (31) ................................... contain different substances which are neither chemically united nor uniformly distributed. 94 Module 2 MOLECULES