Study Notes
Physical changes involve changes in the state of matter without forming new substances, while chemical changes result in new substances with different properties.
- Physical Change — a change where no new substances are formed, and the change is often reversible. Example: Ice melting into water.
- Chemical Change — a change where new substances are formed, often irreversible, and may involve energy changes. Example: A candle burning involves combustion.
- Combustion — a chemical reaction where a substance reacts with oxygen to produce heat and light. Example: Burning of a candle wax.
- Endothermic Reaction — a chemical reaction that absorbs heat from the surroundings. Example: Photosynthesis in plants.
- Exothermic Reaction — a chemical reaction that releases heat. Example: Combustion of fuels.
Exam Tips
Key Definitions to Remember
- Physical Change: A change in state without forming new substances.
- Chemical Change: A reaction that forms new substances with different properties.
- Combustion: A reaction with oxygen that produces heat and light.
Common Confusions
- Confusing physical changes with chemical changes.
- Thinking all changes are irreversible.
Typical Exam Questions
- What is a physical change? A change where no new substances are formed and is often reversible.
- What happens during a chemical change? New substances are formed with different properties.
- Is melting ice a physical or chemical change? It is a physical change.
What Examiners Usually Test
- Understanding the difference between physical and chemical changes.
- Identifying examples of physical and chemical changes.
- Recognizing energy changes in chemical reactions.