glossary

5. substance that helps a chemical reaction to proceed more quicklt
7. combination of symbols that represent a compound; the formula identifies the elements in the compound and the amount of each element
9. the smallest part of an element that is representative of that element;neutral particle made up of a nucleus containing protons and neutrons, and in which the number of electrons equals the number of protons
10. reaction that takes place when two or more substances react to form new substances
12. change of state from a gas to a solid
15. number of protons in the nucleus of one atom of an element
17. principle that matter is not created or destroyed in a chemical reaction; the mass of the products always equals the mass of the reactants
19. chemical reaction that takes place in cells; food (sugar) reacts with oxygen to produce energy, water, and carbon dioxide
20. change of state from a gas to a liquid
22. description of a solid that can be stretched into a long wire
23. orbit of electrons around the nucleus of an atom
25. invisible negatively charged particle that orbits the nucleus of an atom

1. a solution in which water is the solvent
2. also known as amu
3. change of state from a liquid to a gas
4. mass of one atom of an element calculated from the total number of protons,neutrons, and electrons of that atom; measured in atomic mass units (amu)
6. ability of a substance to conduct electricity or heat
8. chemical combination of two or more elements in a specific ratio
11. chemical reaction that absorbs energy
13. description of how a substance interacts with other substances, such as acids;chemical properties are observable only when a chemical change occurs
14. slow chemical change that occurs when oxygen in the air reacts with metal
16. 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
18. catalyst involved in chemical reactions in living things
21. amount of mass in a given volume of a substance
24. pure substances t cannot be broken down into other substances; substance made up of only one type of atom