Procedure:

 

• Heat 150 ml of deionised (DI) water to boiling.

 

• Add approximately 25 g frozen peas.

 

• Bring the water to boil, continue heating for 7 minutes.

 

• Remove the sample from the water and place in the weighing boat.

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• Add 10 ml of vinegar to about 150 ml DI water and determine the pH of the solution. Boil the solution and repeat steps 2 to 4.

 

• Add 10 ml 1 M NaOH to 150 ml DI water and determine the pH of the solution. Boil the solution and repeat steps 2 to 4.

 

• Expose a fourth 25 g sample of peas to a cold mixture of 10 ml vinegar and 150 ml DI water for 7 minutes without cooking. Remove the sample and place in the weighing boat.

 

• Expose a fifth 25 g sample of peas to a cold mixture of 2 g NaHCO3 and dissolve in 150 ml DI water without cooking. Remove the sample and place in the weighing boat.

 

• Set up a sixth weighing boat with canned peas.

 

• Compare all the samples for colour and texture.

 

Common Mistakes Made:

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• Students tend to start the timer for 7 minutes even before the water has started boiling.

 

• Students tend to record the pH of the solution before the pH stabilises. Ensure that the pH stabilises before proceeding to the next step.