chemistry crossword

4. that have a density of 5 or higher e.g., copper, zinc, lead, mercury, cadmium,nickel heavy metals are one type of substance monitored to determine water quality
7. change in the appearance or state of a substance that does not change the composition
12. 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 on
14. a material that electric charge can move through easily
16. neutral particle in the nucleus of an atom
18. description of how a substance interacts with other substances, such as acids;chemical properties are observable only when a chemical change occurs
19. the smallest part of an element that is representative of that element a neutral particle made up of a nucleus containing protons and neutrons, and in which the number of electrons equals the number of protons
21. a table in which the elements are organized by their physical and chemical properties
22. combination of symbols that represent a compound; the formula identifies the elements in the compound and the amount of each element
24. an experiment in which one or more products of a chemical reaction can escape
25. substance that helps a chemical reaction to proceed more quickly

1. positively charged center of an atom;contains protons and neutrons
2. 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
3. group 1 elements in the periodic table, not including hydrogen; the most reactive of the metals
5. group 2 elements in the periodic table; their reactivity is not as strong as that of the alkali metals
6. catalyst involved in chemical reactions in living things
8. a reaction that takes place when two or more substances react to form new substances
9. chemical combination of two or more elements in a specific ratio
10. invisible negatively charged particle that orbits the nucleus of an atom
11. substance that strongly resists the flow of electricity
13. chemical reaction that occurs when oxygen reacts with a substance to form a new substance and give off energy
15. the sum of the number of protons and neutrons in an atom
17. property that describes the physical appearance and composition of a substance
20. new substance produced in a chemical reaction between reactants
23. element that has both metallic and non-metallic properties