Summary
The rate of reaction refers to how quickly reactants are converted into products in a chemical reaction. It can be measured by the change in concentration of reactants or products over time.
- Rate of Reaction — the speed at which reactants are converted into products. Example: Measuring the volume of gas produced over time.
- Activation Energy — the minimum energy required for a reaction to occur. Example: Energy needed for particles to collide successfully.
- Catalyst — a substance that speeds up a reaction without being consumed. Example: Enzymes in biological processes.
- Exothermic Reaction — a reaction that releases energy to the surroundings. Example: Combustion reactions.
- Endothermic Reaction — a reaction that absorbs energy from the surroundings. Example: Thermal decomposition.
Exam Tips
Key Definitions to Remember
- Rate of Reaction: Speed at which reactants turn into products.
- Activation Energy: Minimum energy needed for a reaction.
- Catalyst: Substance that speeds up a reaction without being used up.
Common Confusions
- Exothermic reactions release heat and feel hot, while endothermic reactions absorb heat and feel cold.
- Bond breaking is endothermic, and bond forming is exothermic.
Typical Exam Questions
- Which is a correct definition of rate of reaction? Increase in amount of products against time
- In which of the chemical reactions can the rate be determined by measuring the change in the gas volume? Calcium carbonate with dilute hydrochloric acid
- In an endothermic reaction the products have ........ ? More energy than the reactants
- If the energy required to break the bonds is less than the energy given out by making new bonds the reaction is ...........? Exothermic
What Examiners Usually Test
- Understanding of how changes in concentration, temperature, and surface area affect reaction rates.
- Ability to identify exothermic and endothermic reactions based on energy changes.