Question 1: Define diffusion in your own words.

Answer: Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration, until evenly distributed.

Question 2: Explain how the size and type of particles influence the rate of diffusion.

Answer: Smaller particles diffuse faster than larger ones, and particles that are soluble in lipids diffuse more readily through cell membranes. The type of particle also affects how easily it passes through the membrane.

Question 3: List three factors that affect the rate of diffusion.

Answer: Temperature, concentration gradient, surface area of the membrane, and particle size.

Question 1: A gas diffuses across a membrane at a rate of 5 cm per minute. How long will it take for the gas to diffuse a distance of 20 cm?

Answer: 4 minutes

Question 2: If the concentration difference of a solute across a membrane is doubled, how does this affect the rate of diffusion?

Answer: The rate of diffusion doubles, as it is directly proportional to the concentration gradient.

Question 1: Describe a simple experiment to demonstrate diffusion using agar jelly and food colouring.

Answer: Place drops of food colouring on the surface of agar jelly and observe how the colour spreads through the jelly over time, demonstrating diffusion from an area of higher to lower concentration.

Question 2: Identify three variables that should be controlled in this experiment.

Answer: Temperature, size of the food colouring drops, and the type of agar used.

Question 3: What safety precautions should be taken when handling food colouring and agar jelly?

Answer: Wear gloves to prevent staining and avoid ingestion. Handle agar carefully to prevent cuts or burns if heated.

Question 1: A student observes that the food colouring spreads faster in warm agar compared to cold agar. Explain the scientific reason for this observation.

Answer: An increase in temperature increases the kinetic energy of particles, resulting in a higher diffusion rate.

Question 2: In an experiment, the concentration of solute was higher on one side of the membrane. Over time, the concentration equalised. Describe what this indicates about diffusion.

Answer: It indicates that diffusion is a natural process that moves particles from an area of higher concentration to lower concentration until equilibrium is reached.

Question 1: Describe how the structure of a cell membrane facilitates diffusion of small, non-polar molecules, and explain why this process is vital for cell function. (6 marks)

Answer: The cell membrane is composed of a phospholipid bilayer with embedded proteins, which provides a semi-permeable barrier. Small, non-polar molecules like oxygen and carbon dioxide can diffuse directly through the phospholipid bilayer because they are lipid-soluble and do not require transport proteins. This process is vital for providing cells with oxygen for respiration and removing waste gases, maintaining homeostasis.

Question 1: Explain how understanding diffusion is important in the design of artificial lungs or oxygenators used in medicine.

Answer: Artificial lungs rely on diffusion principles to transfer oxygen into the blood and remove carbon dioxide across a semi-permeable membrane, mimicking natural lung function. Understanding diffusion ensures efficient gas exchange, improving patient outcomes.

Question 2: Describe one technological advancement that utilises diffusion to improve food preservation or packaging.

Answer: Vacuum packaging reduces oxygen availability around food, slowing down diffusion of oxygen into food items and thus inhibiting microbial growth, which extends shelf life.