Chemistry

2. Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe
3. A change that occurs when a sample of matter changes one or more of its physical properties
9. way of presenting information about the chemical proportions of atoms
10. heat energy is released
11. the chemical element with the symbol H
12. The connection between two atoms in a molecule
13. The smallest piece of an element that maintains the identity of that element
14. Atoms of the same element that have different numbers of neutrons
15. a tabular display of the chemical elements

1. The range of values from 0 to 14 that describes the acidity or basicity of a solution
4. a chemical reaction in which one element is replaced by another in a compound
5. defined as the exact opposite of chemical synthesis
6. chemical element with the symbol O
7. chemical bond in which two ions are joined together
8. a chemical element with the symbol Na