Chemical Reactions

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A chemical reaction is a change in matter in which one or more substances change into new substances with entirely different properties. General form: Reactant(s) → Product(s).

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Reactants are the substances that take part in a chemical reaction and undergo change. Products are the new substances formed after the reaction.

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Balanced equation: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + heat and light. Methane and oxygen are reactants. Carbon dioxide and water are products. This is a reaction with release of energy.

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A chemical bond is the attractive force that holds atoms or ions of a molecule together.

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Chemical bonds in the reacting substances break, atoms rearrange, and new bonds form to make new substances. Energy may be absorbed or released during this process.

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Effervescence is the formation of gas bubbles in a liquid during a chemical reaction. Example: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g).

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Balanced equation: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g). Hydrogen gas is evolved with effervescence.

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Balanced equation: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s). The blue solution turns light green and reddish brown copper is deposited. Iron displaces copper because it is more reactive.