Descaling coffee machine
Controlled Assessment
Planning
1) The aim is to find out how fast the reaction is between calcium carbonate and citric acid depending on the concentration.
2) I predict the more concentration of acid there is the faster the reaction will be.
3) The independent variable is the concentration of citric acid.
(0.5mol/dm^3, 0.5, 1.5, 2.0, 2.5,)
4) The dependent variable is the time of reaction (s) to collect 50ml of carbon dioxide.
5) The controlled variable is the volume of water, temperature, the type of citric acid, the amount of Limescale.
6) We will need a beaker, measuring cylinder, gas syringe, stop watch, goggles, clamp stand, water, stirring rod, citric acid, delivery tube, sachets, and calcium carbonate.
Acid |
Time taken for 1 |
50ml of Co2 to 2 |
Be collected 3 |
Average |
|
|
0.5 |
|
|
|
|
|
1.0 |
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|
1.5 |
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2.0 |
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|
2.5 |
How I will minimize errors:
- One person from my group will measure the acid volume to ensure the same eye level was used
- I will use a 20cm^3 measuring cylinder which is the smallest measuring cylinder so we ensure accuracy.
- I will measure the time to 2 decimal places
- I will work in no more than a group of 3
- I will do each experiment 3 times for reliable results