Formative Practice 2.3 – Form 5 Science (KSSM) Chapter 2

Question 1:
What is nitrogen cycle?

Answer:
Nitrogen cycle is a natural cycle that recycles nitrogen between plants and animals, and the atmosphere, soil and water.

Question 2:
(a) Name three processes in the nitrogen cycle which increase nitrate ions in the soil.
(b) Name three processes in the nitrogen cycle which remove nitrate ions from the soil.

Answer:
(a) Lightning or volcanic eruptions, nitrogen fixation, nitrification.

(b) Absorption of nitrate ions from the soil, denitrification, nitrate leaching

Question 3:
How does the planting of legume plants increase the fertility of the soil?

Answer:
Nitrogen-fixing bacteria in the nodules of legume plants use nitrogen from the air to form nitrate ions through nitrogen fixation. Therefore, the fertility of the soil is increased through the addition of nitrate ions to the soil.

Question 4:
What happens to the content of nitrate ions in the soil during rainy season?
Explain your answer.

Answer:
During rainy season, the content of nitrate ions in the soil usually decreases.
Nitrate ions in the soil dissolve in rainwater and flow out from the soil into rivers, underground water or the sea.