EVERYDAY SCIENCE - MATTER
Question 1

Leavening agents are used to make breads and cakes rise during the baking process. They work by producing gases. A common leavening agents is yeast.

Besides yeast, chemical leavening agents such as sodium bicarbonate may also be used.

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Ace wanted to bake a cake. He conducted an experiment with three chemical leavening agents, A, B and C to see which is most suitable for baking a cake.

He placed 3 conical flasks with water and leavening agent on a hot plate set at 80°C. The volume of gas collected in the cylinder was measured over time.

He also prepared a control set-up that is similar to the other three set-ups, except that no leavening agent was added.

The results are shown in this table:

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Answer 1

Fill in the blanks with the keywords provided below.
[gained heat] • [fungi] • [pushed down] • [expanded] • [measuring cylinder] • [occupied space] • [carbon dioxide]

a) State the group of living things that yeast belong to.

Answer:


b) When yeast is added to flour and water, they produce a gas. What gas is produced?

Answer:


c) Explain why the water level in the trough increased over time.

Answer:

The gas produced by the leavening agent travelled into the and at the top. Water was and out into the trough.


d) Based on the results in the table, which leavening agent will cause the cake to expand the most and have the fluffiest texture? (Answer either A, B or C)

Answer:

Using leavening agent will cause the cake to have the fluffiest texture.


e) After 5 minutes, 6 cm3 of gas was collected in the control set-up. Explain why there was gas collected in the cylinder even though no leavening agent was added.

Answer:

The air in the flask from the hot plate and . Air escaped from the flask and occupied space at the top of the cylinder.




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“One tiny yeast grain can contain a million yeast cells.
Watch the video to see millions of yeast cells under a microscope!”