Diffusion

Question 1

Define diffusion including key terms.

Answer 1

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient due to random movement. Net movement means overall movement, and a concentration gradient is the difference between high and low concentration.

Question 2

Explain diffusion using particle theory and an example.

Answer 2

Particles move randomly and collide. For example, hydrogen sulfide gas from a rotten egg spreads from a high concentration area to fill a room evenly.

Question 3

State the factors affecting diffusion.

Answer 3

Surface area, temperature, concentration gradient, distance, molecule size.

Question 4

Surface Area Experiment
Equipment for surface area experiment

Answer 4

Agar jelly (cresol red + alkali), knife, ruler, forceps, test tubes, dilute hydrochloric acid, stopwatch.

Question 5

Method for surface area experiment.

Answer 5

Cut agar into one large cube (1 cm) and four small cubes (0.5 cm). Place in test tubes, add equal acid, and time colour change.

Question 6

Explain results of surface area experiment.

Answer 6

Smaller cubes have higher surface area to volume ratio → faster diffusion → quicker colour change.

Question 7

Errors in the surface area experiment.

Answer 7

Unequal cube sizes, timing inaccuracies, cubes added at different time

Question 8

Equipment for temperature experiment.

Answer 8

Beakers, hot water, cold water, food colouring/potassium permanganate.

Question 9

Method for temperature experiment.

Answer 9

Add dye to hot and cold water without stirring and observe diffusion rate.

Question 10

Explain results of temperature experiment.

Answer 10

Hot water → faster diffusion due to increased kinetic energy (particles have more kinetic energy so they move faster and collide more often).

Question 11

Equipment for ammonia + HCl experiment.

Answer 11

Glass tube, cotton wool, ammonia solution, hydrochloric acid.

Question 12

Method.

Answer 12

Place ammonia at one end, HCl at the other, observe white ring.

Question 13

Explain result.

Answer 13

.Ammonia diffuses faster (ammonia particles are lighter) → ring forms closer to HCl.

Question 14

Describe gas exchange in leaves.

Answer 14

CO₂ diffuses into leaf via stomata for photosynthesis; O₂ diffuses out. Both move down concentration gradients.

Question 15

Describe gas exchange in lungs.

Answer 15

Oxygen diffuses from alveoli to blood; carbon dioxide diffuses from blood to alveoli and is exhaled.

Question 16

Describe absorption in the small intestine.

Answer 16

Villi increase surface area; glucose diffuses into blood from high to low concentration.