Colour mixing:Materials
Introduction It is designed to develop the children's ability to measure volumes of liquid, interpret data and follow directions. Although this activity for older pupils develops measuring to a high level of precision it can be adapted for younger children by scaling up quantities and using larger containers or measuring cylinders with larger divisions / graduations. |
Lesson organisation
Children work in pairs.
Equipment and materials
For each group of 2:
• Challenge sheet (see note 1)
• Red, yellow and blue liquid (see note 2)
• Beakers, 3 (to hold red, yellow and blue liquid)
• Large test-tubes (boiling tubes) (50 ml), 6 (see note 3)
• Test tube rack
• Graduated measuring cylinder (25 ml) (see note 4)
• Graduated measuring cylinder (10 ml) (see note 4)
• Plastic pipette, 1 (see note 5)
• Plastic cup, 1, for rinsing between colours
• Water wash bottles (optional) (Some equipment may be borrowed from a local secondary school)
Technical notes and safety
1 The challenge sheet is the student worksheet. It has the
'challenge', procedure, and results table. See the procedure for details.
2 Fizzy colour tablets, like those from TTS are good as they do not stain.
3 For younger children, or if large test-tubes (boiling tubes) are not available, use small plastic cups.
Test tubes and boiling tubes are glass but are generally robust. However, explain to the children what to do if a tube becomes broken e.g. by being dropped onto a hard fl oor. Explain that they must not try to pick up any broken glass themselves but must report the breakage to the teacher.
4 Use plastic graduated cylinders.
5 Inexpensive disposable type plastic pipettes can be washed.
Click here to see a full list of Health and Safety procedures
Procedure
a Children are read the 'challenge' from the challenge sheet:
'I would like to take this opportunity to welcome you to the Southside Medical Technology Company. If you pass this stage, you will be offered employment at SMTC. As part of our selection process to find the very best candidate possible for employment in our company, we give each applicant who reaches the third round in our selection process a test. This test is based on a person's ability to measure different substances, interpret data and follow directions. Below you will find
the directions to this test. We wish you the best of luck and hope you
have the abilities we are looking for in our employees.'
(OPTIONAL - if you have water wash bottles:)
'Any time you want to "rinse" a piece of equipment use a water wash bottle. Your teacher will tell you how.
Contaminated liquid is disposed of in the plastic cup.'
b Pupils then follow the procedure (also on the challenge sheet):
1 Label 6 test tubes in order: A, B, C, D, E & F.
2 Measure 22 ml of RED liquid from the beaker and pour it into test tube A.
3 Measure 14 ml of YELLOW liquid from the beaker and pour in into test tube C.
4 Measure 18 ml of BLUE liquid from the beaker and pour in into test tube E.
5 From test tube C, measure 3 ml and pour into test tube D.
6 From test tube E, measure 6 ml and pour into test tube D. Swirl test tube D.
7 From test tube E, measure 3 ml and pour into test tube F.
8 From test tube A, measure 6 ml and pour into test tube F. Swirl test tube F.
9 From test tube A, measure 7 ml and pour into test tube B.
10 From test tube C, measure 2 ml and pour into test tube B. Swirl test tube B.
11 Record the colours you have made on the worksheet table.
12 If time permits measure each coloured liquid and record in the table.
c The children record their results in a table where they can record the final colour and the amount of liquid in each test tube.
Teaching notes
Pre-lesson:
Before starting the scientific skills challenge children need to become familiar with graduated cylinders
and the various scales on 25 ml and 10 ml graduated cylinders. Scale markings can be drawn on the board. Children also need to know how to use a pipette.
Simple challenges can help children develop the skills to use a pipette: making a line of single drops on a plastic container lid or piece of cling film, picking up drops using the pipette, adding one drop to an existing drop.
Similar challenges can be set using graduated cylinders: using the 10 ml cylinder can they make exactly
25 ml using 10 ml +10 ml +5 ml (the amount in the 25 ml cylinder will act as a self check), can they fill the 25 ml cylinder with 17 ml of water (the pipette can be used to take away or add liquid and this will be useful in the main activity)?
During the main activity:
How will they label their test tubes (small pieces of paper on the table)? Why is marking or covering the test tubes with paper labels not a good idea (labels could hide the contents)? What strategies can they use to keep track of where they are in the challenge (mark off numbers as they go)?
Children collect the equipment they need but are not allowed to start until the teacher does an equipment
check. Read through the list and when finished let groups get anything they are missing.
Children work independently to complete the challenge. Encourage rinsing of equipment to decrease cross contamination of colours.
At the end the teacher can do a quick accuracy check, each test tube should end up with the same amount, 9 ml. A more precise
'quick check' can be done by pouring all the colours in a graduated cylinder. The total should add to 54 ml. Alternatively, the teacher can get the children to check each others
test tubes and totals.
Click here to download this activity as a Microsoft Word document
Click here to download Graduated Cylinder Activity as a Microsoft Word document
