Summary
Diffusion is the process where particles move from an area of high concentration to an area of low concentration, occurring in gases and liquids due to the random motion of particles. It requires no energy input but happens faster at higher temperatures.
- Diffusion in liquids — movement of particles in a liquid until evenly distributed. Example: Potassium manganate(VII) in water spreads evenly over time.
- Diffusion in gases — faster than in liquids due to higher energy and speed of particles. Example: Bromine gas spreads evenly in air within minutes.
- Molecular mass and diffusion — lighter gases diffuse faster and further than heavier gases. Example: Ammonia diffuses faster than hydrogen chloride, forming ammonium chloride closer to the HCl source.
Exam Tips
Key Definitions to Remember
- Diffusion: Movement of particles from high to low concentration.
- Molecular mass: Affects the rate of diffusion; lighter gases diffuse faster.
Common Confusions
- Diffusion does not require energy input.
- Diffusion is faster in gases than in liquids due to particle speed.
Typical Exam Questions
- Which process is described by particles moving from high to low concentration? Answer: Diffusion.
- What affects the rate of diffusion in gases? Answer: Molecular mass.
- Which example illustrates diffusion? Answer: The smell of cooking spreads through a house.
What Examiners Usually Test
- Understanding of diffusion in different states of matter.
- The effect of molecular mass on the rate of diffusion.