Many students are uncertain of what sources of error are and what to write during practical exam. This article will give your child more confidence when he has some examples of sources of error in his mind when he sits for the practical exam.
What are sources of error?
Sources of error are errors that are inherent in an experiment due to the DESIGN of the experiment. We need to suggest IMPROVEMENT to reduce the sources of error in the experiment.
What are NOT sources of error?
Sources of error are not due to the mistakes made by the student conducting the experiment.
Today, I am going to share with you 3 aspects of design which can cause sources of error to occur.
There are times when an apparatus is chosen due to the ease of use. Hence, the degree of accuracy may be compromised and this can be a source of error for the experiment.
When a measuring cylinder is used to measure 25 cm^3 of a solution instead of a pipette, we can state the source of error this way -> The measuring cylinder used to measure the volume of solution is not as precise as a pipette. It can only measure accurately to 1 cm^3.
The improvement will be -> Use a pipette instead of a measuring cylinder to measure the 25.0 cm^3 volume.
The stability of the reagent used can be a possible source of error if
Hydrogen peroxide decomposes slowly into water and oxygen at room temperature even when no catalyst is added. The rate of decomposition increases with light and heat. Hence, the source of error will be -> Since hydrogen peroxide decomposes into water and oxygen at room temperature, there will be a loss of reagent before and during the experiment.
The improvement will be -> Store hydrogen peroxide in a dark glass bottle, away from light and heat.
3. Dependent variables
When the dependent variable is temperature change, the source of error can be caused by the inherent inaccuracy when temperature is measured.
Heat is always being lost to the surrounding when the surrounding is cooler compared to the reacting mixture. The source of error can be written as -> Heat lost to the surrounding is caused by the poor insulation of the reactants, hence the temperature measured will be lower than expected.
The suggested improvement will be -> Use a polystyrene cup with a cover to minimise heat lost to the surrounding.