Scientists can use a number of methods to determine the concentration of a solution. One way is to make visual comparisons with solutions of known concentrations i.e. ( "Standards")

AimTo determine the concentration of coloured solutions.

Your group will set up a series of standard solutions. You will then be provided with solutions of unknown concentrations. You will attempt to determine how concentrated the unknown solutions are by comparing them to your standards.

Test tube rack
6 large test tubes (> 20 mL)
Water distilled
Food colouring
Solutions of unknown concentration
Burette 50 mL
Retort stand and clamp
Read the method outlined below. Complete a risk assessment prior to performing the experiment
Collect your apparatus.
Set up the test tube rack with the 6 test tubes.
Place a label a number from 1- 6 on the outside of each test tube.
Fill each test tube with 15 mL of water delivered using a burette.
Add 3 drops of food colouring to the second test tube and shake to ensure thorough mixing.
To the remaining test tubes add 5, 7, 9 and 10 drops of food colouring respectively.
Shake each test tube to ensure thorough mixing.
Record observations about the test tubes. You may take a photo of the test tubes but you must also write a description of what you observe.
Collect the test tubes containing solutions of unknown concentration. Compare them to your set of standards and record your results.
Compare your results with another group who used the same food colouring.

Risk Assessment:
Level of risk
Control measures
What to do

Consider the method used in this experiment to determine the concentrations of the unknown solutions. State how reliable you think your method was and justify your decision.

Make a list of possible errors that might have occurred in this experiment that could have affected your results.

Suggest some advantages of the method used in this activity to determine the concentration of the solutions

Suggest some disadvantages of the method used. i.e. Limitations of this method

Suggest some improvements /alternative method that could be used in order to determine the concentrations of unknown solutions.