Answer to Written Practical Question

Bread is made from a mixture of flour, yeast, sugar and water. The dough is kneaded and left to rise before baking. The time taken for the dough to double its size depends on the amount of yeast used.

Plan a laboratory experiment to study the relationship between the amount of yeast used and the time taken for the dough to double its size. The planning of the experiment should include the following aspects:

· Aim of investigation

· Problem statement

· Hypothesis

· Variables

· List of apparatus and materials

· Technique used

· Experimental procedures or methods

· Presentation of data

· Conclusion

ANSWERS

Aim of investigation

To study the relationship between the amount of yeast used and the time taken for the dough to double its size.

Problem statement

What is the effect of the amount of amount of yeast used on the time taken for the dough to double its size?

//How does the amount of yeast used affect the time taken for the dough to double its size?

Hypothesis

The more the amount of yeast used, the faster the time taken for the dough to double its size.

Variables

Manipulated variables: Amount of yeast used

Responding variables: Time taken for the dough to double its size

Fixed variables: Amount of flour// sugar// water (write only one)

Materials

3 g of yeast, 15 g of sugar, 150 g of flour, 150 g of water

Apparatus:

Weighing machine, beakers, mixing bowls, stopwatch

Technique used

Measure and record the time taken for the dough to double its size using a stopwatch.

Procedure

1. Mix 50 g of flour and 5 g of sugar thoroughly in a mixing bowl. Labeled as P. Repeat for mixing bowls Q and R.

2. Mix 0.5 g, 1.0 g and 1.5 g of yeast to mixing bowls P, Q and R respectively.

3. Add 50 ml of water to each mixing bowl and knead for 5 minutes.

4. Place each of the kneaded dough in a beaker and press down the dough. Note the initial level of the dough.

5. Each beaker is covered with a clean cloth and placed in a warm spot.

6. Start the stopwatch and record the time taken for the dough to double its size.

7. The time taken for the dough to double its size for P, Q and R is recorded in a table.

Presentation of data

Mixing bowl	Amount of yeast (g)	The time taken for the dough to double its size (minutes)
P	0.5
Q	1.0
R	1.5

Conclusion

The hypothesis is accepted. The more the amount of yeast used, the faster the time taken for the dough to double its size.