Planning of experiment (Sample 1)

Reactivity of Alkali Metals with water

"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 (2)            (b) Statement of the hypothesis (3)             (c) All the variables(3)            (d) List of substances and apparatus(3)            (e) Procedure of the experiment(3)            (f) Tabulation of data (3)                                         [17 marks]

Suggested Answer:

a)	To compare the reactivity of lithium, sodium and potassium based on the reaction with water. (2 marks)
b)	When going down Group 1, the reactivity towards water increase .
c)	a)       Manipulated variable : type of alkali metals b)       Responding  variable :  reactivity with water c)   Constant variable :        size of alkali metals
d)	M: Lithium, sodium and potassium metals, water, A: basin, knife, forceps.
e)	1.        Lithium metal is cut into a small piece 2.        The paraffin oil on the surface of the metal is wiped with the filter. 3.        A basin is filled with water. 4.   Lithium metal is put on the surface of the water with a pair of forceps. 5.   Reactivity of the reaction/movement of the metals on the water surface is observed and recorded. 6.   The experiment is repeated with sodium and potassium metals.
f)	Metals Observations Lithium Sodium Potassium