Study the following statement
An alloy and a pure metal have a different corrosive resistance characteristic
You are given an iron nail, a steel nail and sodium chloride solution.
a) Suggest a hypothesis to investigate the above statement. (1 m)
An alloy such as a steel nail and a pure metal such as iron nail have different corrosive resistance to sodium chloride solution.
b) Describe an experiment to test your hypothesis in (a) based on the following criteria.
i) Aim of the experiment (1 m)
ii) Identification of variables (2 m)
iii) List of apparatus and materials (1 m)
iv) Procedure or method (4 m)
v) Tabulation of data (1 m)
i) Aim of the experiment : To compare the corrosive resistance of a steel nail and an iron nail to sodium chloride solution
ii) Identification of variables :
Manipulated variable : Purity of the metal – pure metal or alloy
Responding variable : Corrosive resistance of the metal
Fixed variable : Concentration an d volume of sodium chloride solution, length of time the metal is immersed in the sodium chloride solution
iii) Apparatus and materials : Test tubes, test tube rack, sodium chloride solution, iron nail, steel nail
1. Set up the apparatus, immerse the steel nail and iron nail in two different test tube filled with same volume and concentration of sodium chloride.
2. Observe the nails every day for 5 consecutive days and record whether the nails have rusted.
v) Tabulation of data
Type of nail Day 1 Day 2 Day 3 Day 4 Day 5
Steel nail No rust No rust No rust No rust Rust
Iron nail No rust Rust Rust Rust Rust