Chemistry Vocabulary: Part 4

Chemical FormulasA combination of chemical

symbols and numbers to represent a substance

Examples H20: Water

CO2: Carbon Dioxide NaCl: Salt C6H1206: Sugar

Chemical EquationsA representation of a chemical

reaction that uses symbols to show the relationship between the reactants and the products

ExamplesC + O2 CO2

2H2 + O2 2H2O

ReactantsA substance or molecule that

participates in a chemical reaction

ExamplesC + O2 CO2

Reactants

2H2 + O2 2H2O Reactants

ProductsA substance that forms in a

chemical reaction

ExamplesC + O2 CO2

Product

Zn + 2HCl ZnCl2 + H2

Product

SubscriptsA number written below and to

the right of a chemical symbol in a formula

Tells how many atoms of that element are present

Examples CO2

H20

C6H12O6

CoefficientsA number that is placed in front

of a chemical symbol or formulaTells how many molecules of

that substance are presentKeeps reaction balancedExample 2H2 + O2 2H2O

Law of Conservation of MassMass is neither created nor

destroyed in ordinary chemical and physical changes

Must start and end with the same amount

Example

Log + Fire Ashes + Smoke

30 kg 1 kg 28 kg 3 kg