Non Metals And Their Compounds | Competence Based Questions With Answers | Form Four

 

FORM FOUR CHEMISTRY: NON-METALS AND THEIR COMPOUNDS

15 Competence-Based Questions with Answers

1. Chlorine is widely used in the treatment of drinking water.

(a) Explain why chlorine is added to drinking water.
(b) Mention one disadvantage of using excess chlorine in water.

Answer:
(a) Chlorine is added to kill harmful microorganisms such as bacteria and viruses.
(b) Excess chlorine can give water an unpleasant taste and may form harmful compounds.

2. A student passes chlorine gas through moist blue litmus paper.

What observations would you expect?

Answer:
The blue litmus paper first turns red and then becomes bleached/white.

3. Hydrogen chloride gas is prepared in the laboratory by reacting sodium chloride with concentrated sulphuric acid.

(a) Write the balanced chemical equation.
(b) Why is the gas not collected over water?

Answer:
(a)
NaCl + H₂SO₄ → NaHSO₄ + HCl

(b) Hydrogen chloride is highly soluble in water, so it cannot be collected over water.

4. Carbon dioxide is produced when calcium carbonate reacts with dilute hydrochloric acid.

(a) Write the balanced equation.
(b) State one test for carbon dioxide.

Answer:
(a)
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

(b) Bubble the gas through limewater. Limewater turns milky.

5. A farmer discovers that the soil on his farm is too acidic. Explain how a compound of a non-metal can be used to help solve this problem.

Answer:
Calcium carbonate can be added to the soil. It reacts with acids and neutralizes the acidity, raising the soil pH.

6. Sulphur dioxide is released into the atmosphere from industries and burning fuels.

(a) State the environmental problem associated with sulphur dioxide.
(b) Explain how it occurs.

Answer:
(a) It contributes to acid rain.
(b) Sulphur dioxide reacts with oxygen and water in the atmosphere to form acidic substances such as sulphuric acid.

7. A student burns sulphur in air and collects the gas produced.

(a) Name the gas formed.
(b) Give one physical property of the gas.

Answer:
(a) Sulphur dioxide (SO₂).
(b) It is a colourless gas with a choking/pungent smell.

8. Ammonia is an important compound of nitrogen used in agriculture.

(a) Why is ammonia important to farmers?
(b) Give one fertilizer made from ammonia.

Answer:
(a) It is used to manufacture nitrogen fertilizers that supply nitrogen needed for plant growth.
(b) Ammonium nitrate / ammonium sulphate.

9. A student accidentally smells ammonia directly from a reagent bottle.

What is the correct laboratory practice that should have been followed?

Answer:
The student should not smell the gas directly. If instructed to identify the smell, the gas should be gently wafted towards the nose.

10. Nitrogen gas makes up a large proportion of air, but it does not readily support burning.

Explain why nitrogen is useful in food packaging.

Answer:
Nitrogen is relatively unreactive and does not readily react with food. It reduces oxidation and helps preserve food.

11. A candle is placed inside a container containing carbon dioxide. The flame goes out.

(a) Explain the observation.
(b) Give one use of this property of carbon dioxide.

Answer:
(a) Carbon dioxide does not support combustion and displaces oxygen around the flame.
(b) It is used in fire extinguishers.

12. During photosynthesis, green plants use carbon dioxide.

(a) Write the word equation for photosynthesis.
(b) Explain why carbon dioxide is important to plants.

Answer:
(a)
Carbon dioxide + Water → Glucose + Oxygen
(in the presence of light and chlorophyll)

(b) Carbon dioxide provides carbon used by plants to manufacture glucose.

13. A student adds dilute hydrochloric acid to a solution containing silver nitrate and observes a white precipitate.

(a) Name the precipitate formed.
(b) Write the ionic equation.

Answer:
(a) Silver chloride.
(b)
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

14. Hydrogen is considered a useful fuel because it produces water when it burns.

(a) Write the balanced equation for the combustion of hydrogen.
(b) State one advantage of hydrogen as a fuel.

Answer:
(a)
2H₂ + O₂ → 2H₂O

(b) Its combustion produces water and does not directly produce carbon dioxide.

15. A school laboratory has bottles labelled CO₂, H₂, O₂ and Cl₂, but the labels have fallen off. Suggest suitable tests that can be used to identify the gases.

Answer:

• CO₂: Turns limewater milky.
• H₂: Burns with a characteristic “pop” sound when tested carefully with a lighted splint.
• O₂: Relights a glowing splint.
• Cl₂: Bleaches moist litmus paper.

Growth - Competence Based Questions With Answers | Form Four

 

15 Competence-Based Questions with Answers

1. What is growth in living organisms?

Answer: Growth is the permanent and irreversible increase in the size, mass, and number of cells of an organism.

2. A farmer notices that a young plant becomes taller and develops more leaves after several weeks. Explain the biological processes responsible for these changes.

Answer: The increase in height and development of new leaves are results of growth. Growth occurs through cell division, followed by cell enlargement and differentiation. Cell division produces new cells, while enlargement increases their size and differentiation allows them to become specialized tissues.

3. Why is cell division important in the growth of organisms?

Answer: Cell division, particularly mitosis, produces new cells. The increase in the number of cells contributes to an increase in the size and mass of an organism. It also replaces old and damaged cells.

4. Two identical seedlings are planted under the same conditions. One is supplied with enough water while the other receives very little water. After two weeks, the first seedling has grown better. Explain why.

Answer: Water is essential for metabolic activities and maintaining cell turgidity. Adequate water allows normal cell expansion and metabolic processes, while water deficiency reduces these processes and therefore slows growth.

5. Explain why nutrients are important for plant growth.

Answer: Plants require mineral nutrients to manufacture proteins, enzymes, chlorophyll and other substances needed for growth. Nutrients also support cell division and the formation of new tissues.

6. Why does a plant growing in darkness usually have weak and elongated shoots?

Answer: In darkness, the plant cannot carry out photosynthesis effectively, so it produces insufficient food for normal growth. The shoot becomes unusually elongated, thin and weak as it grows towards a possible source of light.

7. Mention four factors that affect growth in human beings.

Answer:

i. Genetic factors
ii. Nutrition
iii. Hormones
iv. Diseases

8. Differentiate between growth and development.

Answer: Growth refers to a permanent and irreversible increase in the size, mass or number of cells of an organism. Development refers to progressive changes in the structure, function and abilities of an organism as it becomes mature.

9. A student wants to investigate the effect of water on the growth of seedlings. Describe how the experiment can be carried out.

Answer: The student should use two similar seedlings planted in similar containers containing equal amounts of soil. One seedling should receive adequate water while the other receives a limited amount. Other factors such as light, temperature and soil type should be kept constant. The height of each seedling should be measured regularly and the results compared.

10. Explain how temperature affects growth.

Answer: Temperature affects the activity of enzymes that control metabolic reactions. At very low temperatures, metabolic reactions become slow, reducing growth. At very high temperatures, enzymes may be denatured, also interfering with growth. Therefore, organisms grow best within a suitable temperature range.

11. Why is a balanced diet important for growth in human beings?

Answer: A balanced diet provides the nutrients required for building new tissues, repairing damaged tissues and supplying energy for metabolic activities. Proteins are particularly important for tissue formation and repair, while vitamins and minerals support normal body functions.

12. A child suffers from severe protein deficiency for a long period. Explain how this condition may affect the child's growth.

Answer: Protein deficiency reduces the body's ability to build and repair tissues. As a result, the child may experience stunted growth, poor muscle development and delayed physical development.

13. Mention four hormones that are associated with growth and development in humans.

Answer: i. Growth hormone
ii. Thyroxine
iii. Oestrogen
iv. Testosterone

14. A farmer removes the shoot tip of a young plant, and the plant later stops increasing in height. Explain this observation.

Answer: The shoot tip contains the apical meristem, which consists of actively dividing cells. These cells produce new cells that contribute to the increase in length of the shoot. Removing the shoot tip therefore reduces primary growth in length.

15. “All organisms grow throughout their entire lives.” Do you agree with this statement? Give reasons for your answer.

Answer: No, I do not completely agree. Growth patterns differ among organisms. Many animals reach a maximum size after attaining maturity, whereas plants can continue growing throughout their lives because they possess meristematic tissues capable of continuous cell division.