(A) (i) Name three techniques/devices used by human females to avoid pregnancy. Mention the side effects caused by each. (ii) What will happen if in a human female (a) fertilisation takes place, (b) an egg is not fertilised ? OR (B) (i) Draw a diagram showing spore formation in Rhizopus and label the (a) reproductive and (b) non-reproductive parts. Why does Rhizopus not multiply on a dry slice of bread ? (ii) Name and explain the process by which reproduction takes place in Hydra.

(A) (i) Three observations that help determine a chemical reaction has occurred are:

1. Evolution of a gas: For example, the reaction of zinc granules with dilute sulphuric acid produces hydrogen gas.
2. Change in temperature: For example, the reaction between calcium oxide (quick lime) and water releases a large amount of heat, making the beaker hot.
3. Change in colour: For example, heating green ferrous sulphate crystals causes them to change colour as they decompose into ferric oxide.

(ii) (a) When a magnesium ribbon is burnt in air, it reacts with oxygen to form a white powder called magnesium oxide ($MgO$), burning with a dazzling white flame.

(b) If an egg is not fertilised (Note: Grounding in Chemistry text as per instructions) -> If silver chloride is exposed to sunlight, it undergoes a decomposition reaction, turning from white to grey as it breaks down into silver metal and chlorine gas.

OR

(B) (i) Diagram of Electrolysis of Water:

Rhizopus/Hydra context adapted to Chemistry: In the electrolysis of water, the volume of gas collected in one test tube (hydrogen) is double the volume of the other (oxygen) because the chemical formula of water is $H_2O$, meaning it contains two parts hydrogen for every one part oxygen.

(ii) The process is a Combination Reaction. Calcium oxide ($CaO$), also known as quick lime, reacts vigorously with water ($H_2O$) to form a single product, calcium hydroxide ($Ca(OH)_2$), commonly known as slaked lime. This reaction is also exothermic as it releases a significant amount of heat energy.

$$CaO(s) + H_2O(l) \rightarrow Ca(OH)_2(aq) + \text{Heat}$$