Experimental Controls
For the experiment to be considered fair, it was very important to minimise the effect of external factors and variables. These were known as controlled variables. Controlled variables, which were not kept consistent amongst all testings and throughout the entire investigation, would compromise the accuracy and precision of the experiment.
As such, it was important to keep these consistent throughout the experiment, and ensure that the only change was the independent variable. Controlled variables included:
· Material of the glasses (different material glasses could potentially interfere with the rate of heat absorption, so identical material glasses were used)
· Shape of the glasses (different shapes may be able to absorb heat at a faster rate than others, so an attempt was made to use similar/identically shaped glasses)
· Rate of cooling (although all glasses began at the same temperature, different rates of cooling, would also affect the rates of heating, so the initial temperature of the water in the refrigerator was made the same temperature as the refrigerator, so that the rate of cooling was virtually nothing)
· Positioning (it was important to place the glasses in the exact same position every time, under the same exposure to light)
· Temperature of room (the experiment was done at a time when the temperature was relatively stable, so as to not introduce an external heat factor)
· Amount of water (this was kept constant by using a measuring cylinder)
To ensure that the results of the experiment accurately reflected the effect that colour has on the rate at which heat is absorbed, an experimental control had to be run. An experimental control is run when there is an absence of the independent variable. In this case, the experimental control was run, with the clear glass, to see the normal rate at which heat is absorbed under identical condition, with the absence of colour.
This is done, so that a comparison can be done between when there is an absence of colour and when colour is present. The contrast, or difference in results, can be used to determine the extent to which colour has an effect on heat absorption and is useful as it provides a starting point or ‘original value’ to refer to.
As such, it was important to keep these consistent throughout the experiment, and ensure that the only change was the independent variable. Controlled variables included:
· Material of the glasses (different material glasses could potentially interfere with the rate of heat absorption, so identical material glasses were used)
· Shape of the glasses (different shapes may be able to absorb heat at a faster rate than others, so an attempt was made to use similar/identically shaped glasses)
· Rate of cooling (although all glasses began at the same temperature, different rates of cooling, would also affect the rates of heating, so the initial temperature of the water in the refrigerator was made the same temperature as the refrigerator, so that the rate of cooling was virtually nothing)
· Positioning (it was important to place the glasses in the exact same position every time, under the same exposure to light)
· Temperature of room (the experiment was done at a time when the temperature was relatively stable, so as to not introduce an external heat factor)
· Amount of water (this was kept constant by using a measuring cylinder)
To ensure that the results of the experiment accurately reflected the effect that colour has on the rate at which heat is absorbed, an experimental control had to be run. An experimental control is run when there is an absence of the independent variable. In this case, the experimental control was run, with the clear glass, to see the normal rate at which heat is absorbed under identical condition, with the absence of colour.
This is done, so that a comparison can be done between when there is an absence of colour and when colour is present. The contrast, or difference in results, can be used to determine the extent to which colour has an effect on heat absorption and is useful as it provides a starting point or ‘original value’ to refer to.