| A | B |
|---|
| matter | anything that has mass and occupies space |
| mass | the quantity of matter an object has |
| elements | pure substances that cannot be broken down chemically into anything simpler |
| atom | the smallest particle of an element |
| nucleus (atomic) | the central core of an atom containing protons and neutrons |
| proton | a positively charged subatomic particle |
| neutron | a subatomic particle found in the nucleus without an electrical charge |
| atomic number | the number of protons in an atom |
| electrons | negatively charged subatomic particles that orbit the nucleus |
| energy levels | are occupied by electrons with different amounts of energy |
| compound | a pure substance made of two or more elements |
| chemical reactions | when chemical bonds are broken and atoms recombine and form new bonds |
| chemical bonds | attachments that atoms form with each other |
| covalent bond | atoms combine by sharing electrons |
| molecule | 2 or more atoms combined covalently |
| ionic bonds | atoms attract each other to form compounds by transferring electrons |
| free energy | energy in a system available for work |
| reactants | all substances going into a chemical reaction |
| products | all substances coming out of a chemical reaction |
| exergonic reactions | release more energy than goes into starting it |
| endergonic reactions | take more energy to keep it going than what comes out |
| activation energy | the energy it takes to get a chemical reaction going |
| catalysts | substances that reduce activation energy |
| enzymes | catalysts in living things made of proteins |
| oxidation reaction | a reactant loses one or more electrons and becomes more positive |
| reduction reaction | a reactant gains one or more electrons to become more negative |
| dissociation | the breaking apart of water molecules into two ions of opposite charge |
| hydroxide ion | OH- |
| hydronium ion | H+ |
| acid | a solution in which hydronium ions outnumber hydroxide ions |
| base | a solution in which hydroxide ions outnumber hydronium ions |
| pH scale | ranges from very acidic 0 to very basic 14 |
| buffers | chemicals substances that neutralize small amounts of either acidic or basic solutions |
