Invest8gat8ng ph

Created by

sntiger

Cards (7)

Equipment
A 5 cm³ measuring cylinder or syringe
Dimple spotting tile
Starch solution
Buffer solutions with a range of pH values
Test tubes, to mix the starch solution and buffer solutions in
Amylase solution, to add to the starch and buffer solutions and start the reaction
Distilled water, to use as a control
A water bath (electrical or a Bunsen burner and beaker) at 35 °C
A thermometer, to measure the temperature of the water bath and make sure it's constant
Pipettes, to sample the test tube mixtures
lodine solution, to test the samples for starch
A stopwatch, to time when to take samples
Method
1. Set up a water bath at 35°C
2. Put one drop of iodine solution into each dimple in the spotting tile
3. Measure 5 cm³ of starch solution and 2 cm³ of a buffer solution into 2 test tubes
4. Record the pH of the buffer solution you are using
5. Place both test tubes in the water bath and allow a few minutes for them to reach the same temperature as the water bath
6. Add 5 cm³ of amylase solution to one of the test tubes and 2 cm³ of distilled water to the other
7. Start the stopwatch
8. After 30 seconds, use 2 pipettes to transfer a few drops of each test tube mixture onto the spotting tile
9. Observe if the iodine on the spotting tile turns blue-black
10. Repeat steps 5-7 every 30 seconds until the mixture with amylase stops turning iodine blue-black
11. Record the time it took for the iodine to stop turning blue-black in your results table
12. Repeat the method for the remaining buffer solutions
The test tube with distilled water will act as a control.
If the mixture with amylase turns iodine blue-black, the amylase still has starch to break down.
The control mixture will always turn iodine blue-black, if it doesn't your results won't be valid (as something other than amylase may be breaking down the starch).
What is the independent variable()
Ph of buffer solution
What is dependent variable(measure) 
Rate of starch breakdown