Sample Question For Paper 3

“When lithium metal is put in water, it moves very slowly on the surface of the water. When sodium metal is put in water, it moves quite fast and produces “hiss” sound. When potassium metal is put in water, it moves very fast and produces small explosions”.

Plan an experiment in the laboratory to investigate the reactivity of lithium, sodium and potassium with water. The planning of your experiment must consist of the following:

(a) Aim of experiment

(b) Statement of the hypothesis

(c) All the variables

(d) List of substances and apparatus

(e) Procedure of the experiment

(f) Tabulation of data

[17 marks]

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Sample Answer:

Aim	To determine the reactivity of alkali metals with water.
Problem statement	How do Group 1 elements do reacts with water?
Variables	MV: Different types of alkali metals RV: Reactivity of alkali metals FV: size of alkali metals
Hypothesis	Alkali metals become more reactive in reaction with water when going down Group 1.
Apparatus & Materials	A: forceps, knife M: small piece of lithium, sodium, potassium, filter paper, distilled water.
Procedure	1. Cut a small piece of lithium using forceps and knife. 2. Dry the oil on the surface of lithium with filter paper. 3. Place the lithium on the surface of water in a trough. 4. Record the reactivity of lithium with water. 5. Repeat steps 1 to 4 using potassium and sodium.
Tabulation of data	Types of alkali metals Reactivity with water Lithium Sodium potassium