science in action 9 : chemistry

WHMIS

Workplace Hazardous Materials Information System; a system of easy-to-see warning symbols on hazardous materials

atom

the smallest part of an element that is representative of that element; a neutral particle is made up of a nucleus containing protons and neutrons, and in which the number of electrons equals the number of protons

ion

atom that has become electrically charged because it has lost or gained electrons; a positive ion is an atom that has lost one or more electrons; a negative ion is an atom that has gained one or more electrons

ionic compound

pure substance formed when at least one metal and one non-metal combine

molecule

group of atoms joined by covalent bonds

molecular compound

pure substance formed when non-metals combine

chemical change

change that results when two or more substances react to create a different substance or substances; the new substances have completely different properties from the original ones

proton

positively charged particle in the nucleus of an atom

electron

invisible negatively charged particle that orbits the nucleus of an atom

neutron

neutral particle in the nucleus of an atom

periodic table

a table in which the elements are organized by their physical and chemical properties

family

vertical column of elements in the periodic table; elements in a family all have similar chemical properties; also called a group

period

horizontal row of elements in the periodic table; also called an orbit

chemical property

description of how a substance interacts with other substances, such as acids; chemical properties are observable only when a chemical change occurs

physical property

property that describes the physical appearance and composition of a substance

physical change

change in the appearance or state of a substance that does not change the composition

law of conservation of mass

the total mass of the products always equals the total mass of the reactants in any chemical reaction; same atoms with a different arrangement

states of matter

refers to the three common states in which matter can exist: solid, liquid, and gas

freezing

change of state from a liquid to a solid

melting

change of state from a solid to a liquid

evaporation

change of state from a liquid to a gas

condensation

change of state from a gas to a liquid

desposition

change of state from a gas to a solid

sublimation

change of state from a solid to a gas or from a gas to a solid

reactant

substance that reacts with another substance or substances in a chemical reaction to create new substances with different properties

metal

shiny, malleable, ductile element that conducts electricity

non-metal

dull, brittle element that does not conduct electricity

metalloid

element that has both metallic and non-metallic properties

combustion

chemical reaction that occurs when oxygen reacts with a substance to form a new substance and give off energy

corrosion

slow chemical change that occurs when oxygen in the air reacts with a metal

cellular respiration

chemical reaction that takes place in cells; food (sugar) reacts with oxygen to produce energy, water, and carbon dioxide

variable

anything that can change in an experiment

manipulated variable

the factor of an experiment that is changed on purpose

responding variable

the result that is observed and likely changes in response to the manipulated variable

controlled variable

the experimental element which is constant and unchanged throughout the course of the experiment

catalyst

substance that helps a chemical reaction to proceed more quickly

enzyme

catalyst involved in chemical reactions in living things; biological catalyst