A 100 W heater is connected to a 240 V mains supply. Calculate: the current drawn; (ii) the resistance of the heater. b. (i) List three compounds that have electrovalent bonds. (ii) Give two characteristics of electrovalent compounds. C. (i) What is the rhesus factor? (ii) Briefly explain how the rhesus factor in humans could result in miscarriage. a. (i) Explain briefly how solar energy is used to generate electricity. (ii) State two other uses of solar energy. b. State five ways of conserving water in the home. C. (i) State three management practices that ensure high yield in maize production. (ii) Explain how two of the practices stated in (i) help to ensure high yield of maize. d. (i) State two effects of air masses on the environment. (ii) State three ways by which global warming can be reduced. a. (i) Explain why aluminium resists corrosion but iron does not. (ii) State two methods of preventing iron from rusting. b. (i) Explain the term culling as used in livestock management. (ii) State three benefits of practising culling. C. (i) Distinguish between grafting and budding. (ii) Give three reasons for grafting and budding. d. (i) State the principle of conservation of energy. (ii) State the energy transformations that occur in each of the following devices: a moving motorcycle; a television set in operation. a. (i) What are secondary colours of light? (ii) Name the colour that results from combining each of the following pairs of colours of light: red and green; blue and green; red and blue. b. (i) Define the mole of a substance. (ii) Calculate the number of atoms in 18 g of magnesium metal. [Mg = 24, Avogadro number = 6.023 × 10²³] C. (i) Differentiate between bone and cartilage. (ii) Name three parts of the human body where cartilages are found. d. (i) Explain the term deep litter system as used in poultry. (ii) Give three advantages of the deep litter system.

4. a. (i) Secondary colours of light are colours formed by mixing two primary colours of light in equal proportions. The primary colours of light are red, green, and blue. 4. a. (ii) (a) Red and green combine to form yellow. (b) Blue and green combine to form cyan. (c) Red and blue combine to form magenta. 4. b. (i) The mole of a substance is the amount of substance that contains as many elementary entities (atoms, molecules, ions, etc.) as there are atoms in 12 grams of carbon-12. This number is Avogadro's number, approximately 6.023 × 10^23. 4. b. (ii) Step 1: Calculate the number of moles of magnesium. Moles = MassMolar mass Moles of Mg = 18 g24 g/mol = 0.75 mol Step 2: Calculate the number of atoms. Number of atoms = Moles × Avogadro number Number of atoms = 0.75 mol × 6.023 × 10^23 atoms/mol Number of atoms = 4.51725 × 10^23 atoms The number of atoms in 18 g of magnesium metal is 4.51725 × 10^23 atoms. 4. c. (i) • Bone is a hard, rigid connective tissue that forms the skeleton, providing structural support and protection. It is highly vascularized and contains calcium salts. • Cartilage is a flexible, elastic connective tissue that is softer than bone. It provides cushioning, reduces friction in joints, and maintains the shape of certain body parts. It is avascular. 4. c. (ii) Cartilages are found in the following parts of the human body: Nose Ears Trachea (windpipe) Between vertebrae (intervertebral discs) Ends of long bones (articular cartilage) 4. d. (i) The deep litter system in poultry is a method where poultry are kept on a thick layer of absorbent material (such as wood shavings, straw, or rice hulls) that accumulates over time. This litter is allowed to build up and decompose, providing insulation and reducing the need for frequent cleaning. 4. d. (ii) Three advantages of the deep litter system are: It provides insulation, keeping the birds warm in cold weather. The decomposition of litter generates heat and produces organic fertilizer. It reduces labor costs associated with frequent cleaning and waste removal. That's 2 down. 3 left today — send the next one.