State any two physical properties of sodium chloride.

Here are the answers to the questions:

4. (a) (i) State any two physical properties of sodium chloride.

1. It is a white crystalline solid.
2. It has a high melting point.

4. (a) (ii) Indigestion is caused by too much dilute hydrochloric acid in the stomach. It is cured by ingesting anti-acid tablets. State, with a reason, the acid-base nature of the chemical present in the anti-acid tablet.
The chemical present in the anti-acid tablet is basic.
Reason: It neutralizes the excess hydrochloric acid in the stomach.

4. (b) Iron is extracted from an iron compound found in haematite. Name the iron compound in haematite.
The iron compound in haematite is iron(III) oxide (or ferric oxide).

5. (a) (i) Two other solid raw materials are fed into the blast furnace together with haematite. Name the two raw materials and state a function for each of these materials.

1. Raw material: Coke Function: Acts as a fuel to provide heat and produces carbon monoxide for reduction.
2. Raw material: Limestone Function: Acts as a flux to remove acidic impurities by forming slag.

5. (a) (ii) Fig. 5.1 shows a stroke in the operation of an engine. Identify, giving two reasons, the stroke shown.
Stroke: Power stroke (or expansion stroke)
Reasons:

1. Both the inlet valve and exhaust valve are closed.
2. The piston is moving downwards due to the expansion of hot gases after combustion.

5. (b) (i) State the role of a fuel injector in a petrol engine.
The role of a fuel injector is to atomize and spray a precise amount of fuel into the engine's intake manifold or combustion chamber.

5. (b) (ii) State the role of a carburettor.
The role of a carburettor is to mix air and fuel in the correct ratio for combustion in an internal combustion engine.

5. (b) (iii) Explain the advantage of a fuel injector over a carburettor.
Fuel injectors provide more precise control over the air-fuel mixture, leading to better fuel efficiency and reduced emissions compared to carburettors.