Chemistry vocab

3. a substance that is not uniform throughout
4. change a change of one substance into another substance
6. an atom of one element that has a different number of neutrons than another atom of the same element
8. a combination of two or more substances that do not combine chemically, but remain the same individual substances
9. a substance formed by a chemical reaction, made by the rearrangement of atoms in bonds and reactants
11. a substance that is evenly spread throughout. Particles not distinguishable.
13. a group of atoms that are held together by covalent bonds so that they move together
15. mass number the total number of protons and neutrons in an atoms nucleus
16. a neutral part, located in an atoms nucleus
18. change a usually reversible change in the physical properties of a substance, as size and shape
21. a substance that is present at the beginning of a chemical reaction, takes part in the reaction, and is changed into a new substance
22. a solid substance, that forms as a result of a chemical reaction between chemicals in two liquids

1. the number written slightly below into the rate of a chemical symbol that shows how many atoms of an element are in a compound
2. a substance made up of two or more different types of atoms bonded together
5. a substance that cannot be broken down into a simpler substances by ordinary chemical changes
7. a horizontal row in the periodic table of the elements that have varying properties
9. of positively charged particle, located in an atoms nucleus
10. an atom of group of atoms that has a positive or negative electric charge, forms by gaining or losing electrons
12. a negatively charged particle located outside of an atoms nucleus about 2000 times smaller than either a proton or neutron
14. the number before a chemical formula indicating how many molecules are involved in a chemical reaction
17. a substance that increases the rate of a chemical reaction, but is not consumed by the reaction
19. a vertical column in the periodic table of the elements that have similar properties
20. number the total number of protons in an atoms nucleus