Hypothesis
Group 2 metal ions cause hardness in water
Equipment
- 6 samples of water each containing different metal ions
- Soap solution
- Conical flask (small)
- Pipette
- Measuring cylinder
Method
Take the first sample and pour 10 centimetres cubed of it into the conical flask. Add 1 cm cubed of soap solution using the pipette, put a stopper in the top of the conical flask and shake the flask for 10 seconds. Observe the lather that's formed on the top of the water - if it lasts for longer than 1 minute then we can consider it to be a permanent lather and we can record that. If the lather fades away after less than a minute add another centimetre cubed and repeat. Keep doing this until the lather does persist for at least a minute. Record how much soap solution was required to produce a permanent lather with that metal ion present and repeat the whole process for the remaining metal ions.
Variables
Independent variable - type of metal ion
Dependent variable - Volume of soap solution required to produce a permanent lather
Control variable - Amount of shaking, type of soap solution used, type of flask used
Risk Assessment
This is a very safe experiment (i.e. low risk). Care must be taken with spillages and they must be wiped up immediately.