Aim: To investigate how the concentration affects the rate of diffusion of hydrochloric acid through agar blocks
Research Question: To determine how will different concentrations (0.1M, 0.2M, 0.3M, 0.4M, 0.5M) of hydrochloric acid affect the rate of diffusion of sodium chloride through agar blocks?
Introduction-include prediction; information you have researched before
Diffusion refers to the passive movement of molecules along the concentration gradient. In this case we will be looking at the diffusion of acid in agar blocks. Agar is a jelly like substance and the indicator methyl orange is added which will turn red in the presence of acid. Hence we can measure the time taken for the colour change to calculate the rate of diffusion of hydrochloric acid in agar blocks.
Variables
Independent variable
Concentration of hydrochloric acid
Range
0.1M, 0.2M, 0.3M, 0.4M, 0.5M
Dependent variable
Time taken for agar blocks to fully change colour
How it is measured/units
Using a stopwatch the time will be recorded for the change in colour in seconds.
Controlled variables (min 3)
Controlled variables
1. Volume of hydrochloric acid
2. Temperature of surroundings
3. Type of acid used
4. Type of agar blocks used
List of materials/equipment
Uncertainty of apparatus
No.
Apparatus/equipment
Quantity
Uncertainty(±)
1
10.0cm³ measuring cylinder
1
0.1 cm³
2
25.0cm³ measuring cylinder
1
0.5cm³
3
100cm³ measuring cylinder
1
1 cm³
4
Ruler
1
0.05cm
5
Stopwatch
1
1s
6
Beaker
5
-
7
Thermometer
5
0.2°C
8
Bunsen Burner
5
-
9
Scalpel
1
-
Procedure
Control of variables
Independent variable
Concentration of hydrochloric acid
Range
How it is monitored
0.1M, 0.2M, 0.3M, 0.4M, 0.5M
Controlled by using 0.1M, 0.2M, 0.3M, 0.4M, 0.5M respectively. The different concentration of acid is made by mixing hydrochloric