The provided text appears to be a solution set to a biology or general science test. The original question would likely have been a series of short-answer questions covering excretion, plant propagati

Here are the solutions to all the questions:

1 (a) (i) Name three substances that are excreted from human body.

• Urea
• Carbon dioxide
• Sweat

1 (a) (ii) Name two organs in humans which perform excretory function.

• Kidneys
• Lungs

1 (b) (i) What is grafting used in crop production?
Grafting is a horticultural technique where tissues of plants are joined so as to continue their growth together as one plant. It is used to combine desirable characteristics from two different plants, such as a strong rootstock with a high-yielding scion.

1 (b) (ii) State three benefits of grafting.

• Allows for the propagation of plants that do not root easily from cuttings.
• Can impart disease resistance or pest resistance from the rootstock to the scion.
• Enables faster fruiting or flowering compared to growing from seed.

1 (c) (i) State two ways in which scientific methods is important.

• It provides a systematic approach to problem-solving and understanding the natural world.
• It allows for the development of new technologies and innovations based on empirical evidence.

1 (c) (ii) Give one reason for each of the following laboratory rules:

• (α) do not wear rubber slippers to the laboratory: To protect feet from chemical spills, broken glass, or electrical hazards and provide better grip.
• (β) close all taps before leaving the laboratory: To prevent flooding and conserve water.
• (γ) spilled liquids must be cleaned immediately: To prevent slips and falls, and to avoid contamination or damage to equipment/surfaces.

1 (d) (i) Explain briefly the term earthing as used in household wiring.
Earthing is a safety measure in electrical wiring where the metal casing of an appliance is connected to the ground via a low-resistance wire. This provides a safe path for fault current to flow directly into the earth, preventing electric shock if a live wire touches the casing.

1 (d) (ii) Name two sources of electric power generation.

• Hydroelectric power
• Thermal power (e.g., from coal, natural gas)

2 (a) Give four reasons why farmers should be discouraged from using chemical fertilizers.

• They can lead to water pollution (eutrophication) when runoff enters rivers and lakes.
• Overuse can cause soil degradation, reducing its natural fertility and microbial activity over time.
• They can be expensive, increasing production costs for farmers.
• Improper handling or application can pose health risks to farmers and consumers.

2 (b) (i) What is temporary hard water?
Temporary hard water is water that contains dissolved calcium hydrogen carbonate (Ca(HCO$_3$)$_2$) and/or magnesium hydrogen carbonate (Mg(HCO$_3$)$_2$). It can be softened by boiling, which precipitates the carbonates.

2 (b) (ii) Write a chemical equation to show how temporary hard water can be softened by heating.

$$\text{Ca(HCO}_3\text{)}_2\text{(aq)} \xrightarrow{\text{heat}} \text{CaCO}_3\text{(s)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}$$

2 (c) (i) What is a lever?
A lever is a simple machine consisting of a rigid bar or beam that pivots around a fixed point called a fulcrum, used to multiply force or change the direction of force.

2 (c) (ii) Explain each of the following terms as applied to simple machines:

• (α) mechanical advantage: The ratio of the load (resistance force) to the effort (applied force). It indicates how much a machine multiplies the input force.
• (β) velocity ratio: The ratio of the distance moved by the effort to the distance moved by the load in the same amount of time. It is a theoretical value determined by the machine's design.

2 (d) (i) What is food processing?
Food processing is the transformation of raw ingredients into food, or of food into other forms, through physical or chemical means. It involves various techniques to prepare food for consumption, storage, or marketing.

2 (d) (ii) State:

• (α) two advantages of food processing:
  • Increases shelf life and prevents spoilage, making food available for longer periods.
  • Enhances convenience for consumers, reducing preparation time.
• (β) one disadvantage of food processing:
  • Can lead to a loss of essential nutrients (e.g., vitamins) during processing.