Question 20
Think like a scientist: Making different concentrations of a solution
You will need: safety glasses; test tubes; test tube rack; pipette; two measuring cylinders, suitable for measuring 10 cm³; concentrated solution of food dye; beaker of water.
Method
1 Carefully measure out 10 cm³ of the concentrated food dye solution. When you have added about the correct volume you can use the pipette to add or remove the final amount drop-by-drop, so that your measurement is as accurate as possible. Place it in a test tube and leave it in the test tube rack. This is solution A.
2 Carefully measure another 8 cm³ of the concentrated food dye solution. Pour it into a test tube.
3 Measure out 2 cm³ water and add it to the 8 cm³ of food dye. Leave it in the test tube rack. This is solution B.
4 Use the table below to make up food dye solutions C, D and E. Place the solutions in the test tube rack, in order, from A–E.
| Solution | Volume of concentrated food dye solution in cm³ | Volume of water in cm³ | Total volume in cm³ |
|---|---:|---:|---:|
| A | 10 | 0 | 10 |
| B | 8 | 2 | 10 |
| C | 6 | 4 | 10 |
| D | 4 | 6 | 10 |
| E | 2 | 8 | 10 |
5 Look carefully at the solutions you have made.
Compare the number of particles of food dye in the most concentrated solution of food dye and the most dilute solution.
You will need: safety glasses; test tubes; test tube rack; pipette; two measuring cylinders, suitable for measuring 10 cm³; concentrated solution of food dye; beaker of water.
Method
1 Carefully measure out 10 cm³ of the concentrated food dye solution. When you have added about the correct volume you can use the pipette to add or remove the final amount drop-by-drop, so that your measurement is as accurate as possible. Place it in a test tube and leave it in the test tube rack. This is solution A.
2 Carefully measure another 8 cm³ of the concentrated food dye solution. Pour it into a test tube.
3 Measure out 2 cm³ water and add it to the 8 cm³ of food dye. Leave it in the test tube rack. This is solution B.
4 Use the table below to make up food dye solutions C, D and E. Place the solutions in the test tube rack, in order, from A–E.
| Solution | Volume of concentrated food dye solution in cm³ | Volume of water in cm³ | Total volume in cm³ |
|---|---:|---:|---:|
| A | 10 | 0 | 10 |
| B | 8 | 2 | 10 |
| C | 6 | 4 | 10 |
| D | 4 | 6 | 10 |
| E | 2 | 8 | 10 |
5 Look carefully at the solutions you have made.
Compare the number of particles of food dye in the most concentrated solution of food dye and the most dilute solution.
