Define mechanical energy, calculate potential energy, distinguish between alkali and base, and name sources of bases.

$$PE = mgh$$ $$PE = (10 \text{ kg})(10 \text{ m/s}^2)(2 \text{ m})$$ $$PE = 200 \text{ J}$$

The potential energy possessed by the body is $\boxed{\textbf{200 J}}$.

Question 2(c)(i): Distinguish between an alkali and a base.
A base is a substance that can accept hydrogen ions or donate a pair of valence electrons. An alkali is a soluble base that dissolves in water to produce hydroxide ions ($\text{OH}^-$). All alkalis are bases, but not all bases are alkalis.

Question 2(c)(ii): Name one natural source of each of the following bases:

• (α) Ammonia: Decomposition of organic matter (e.g., urea in urine).
• (β) Calcium oxide: Limestone (calcium carbonate, which is heated to produce calcium oxide).
• (γ) Potassium hydroxide: Wood ash.

Question 2(d)(i): Explain the term mulching.
Mulching is the practice of covering the soil surface with a layer of material (mulch) to conserve soil moisture, suppress weed growth, regulate soil temperature, and improve soil health.

Question 2(d)(ii): List three materials used for mulching.

1. Straw
2. Wood chips
3. Leaves

Question 4(a)(i): Differentiate between pest and parasite.
A pest is an organism that causes damage or nuisance to humans, their crops, livestock, or property. A parasite is an organism that lives on or in a host organism, obtaining nutrients from the host and often causing harm, but typically not killing the host immediately.

Question 4(a)(ii): Name the stages in the life cycle of a weevil.
The stages in the life cycle of a weevil (complete metamorphosis) are:

1. Egg
2. Larva
3. Pupa
4. Adult

Question 4(b)(i): Calculate the concentration of the solution in mol dm⁻³.
Given: Mass of KOH $= 25$ g, Volume of solution $= 250$ cm³, Molar masses: K $= 39.0$, O $= 16$, H $= 1$.

$$\text{Concentration} = \frac{\text{moles}}{\text{volume}} = \frac{0.4464 \text{ mol}}{0.250 \text{ dm}^3} \approx 1.7856 \text{ mol/dm}^3$$

The concentration of the solution is approximately $\boxed{\textbf{1.79 mol/dm}^3}$.

Question 4(b)(ii): Calculate the concentration of the diluted solution in mol dm⁻³.
Given: Initial concentration $C_1 = 1.7856$ mol/dm³ (from part i), Initial volume $V_1 = 125$ cm³, Final volume $V_2 = 1000$ cm³.

$$C_2 = \frac{(1.7856 \text{ mol/dm}^3)(125 \text{ cm}^3)}{1000 \text{ cm}^3}$$ $$C_2 = \frac{223.2}{1000} \text{ mol/dm}^3$$ $$C_2 = 0.2232 \text{ mol/dm}^3$$

The concentration of the diluted solution is approximately $\boxed{\textbf{0.223 mol/dm}^3}$.

Question 4(c): Name the discrete electronic component described by each of the following statements:

• (i) It stores electric charge: Capacitor
• (ii) It stores magnetic field when electric current flows through it: Inductor (or Coil)
• (iii) It opposes the flow of electric charge: Resistor
• (iv) It is made of two parallel plates separated by an insulator: Capacitor
• (v) It allows electric current to flow in one direction only: Diode