Physical Science / Unit 5: Chemical Reactions
5.1 Chemical Equations
Notes
A chemical reaction rearranges atoms into new substances. A chemical equation shows it with symbols.
- Reactants are on the left, products on the right, with an arrow meaning "yields": $\text{C} + \text{O}_2 \rightarrow \text{CO}_2$.
- State symbols: (s) solid, (l) liquid, (g) gas, (aq) dissolved in water.
- Coefficients are the numbers in front of formulas; subscripts are never changed when balancing.
- Signs a reaction occurred: gas bubbles, color change, precipitate, temperature change, light.
Practice
In the equation $\text{2H}_2 + \text{O}_2 \rightarrow \text{2H}_2\text{O}$, what are the reactants?
Reactants are the substances on the left of the arrow.
In an equation, the number in front of a formula is called a:
Coefficients tell how many units of the substance are involved.
What does the symbol (aq) mean after a formula?
(aq) stands for aqueous.
Ready for more? Take the Unit 5 test.