Mastering Biology Sba Workbook Answers

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Suggested answers to Practical Workbook for SBA

Ch 1Introducing biology

Practical 1.1Design an investigation of the effect of fresh pineapple on the setting of jelly

Propose a hypothesis (p. 1-2)
It is the fresh pineapple that causes the jelly to remain in liquid form.

Design and perform an experiment (p. 1-2)
1(Answer varies with Ss. The recommended quantity of jelly powder and water is stated on the packet of the jelly powder. Jelly will not set if it is too dilute.)

2Method II. This makes sure the concentrations of the jelly solutions in different containers are the same.

AIdentifying variables
|Independent variable |Dependent variable |Controlled variables |Control | |(What will you change?) |(What will you measure?) |(What will you keep constant?) |(What is the control in this | | | | |experiment?) | |The presence of fresh pineapple. |Whether the jelly set or not. |The amount of jelly solution in |The jelly without fresh | | | |each container, the size and |pineapple. | | | |shape of the containers, the | | | | |cooling temperature, the time | | | | |allowed for setting, etc. | |

BDesigning the set-up
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CCollecting data
1(Answer varies with Ss.)
2Repeat the experiment a few more times.

DRisk assessment and safety precautions
1During the preparation of jelly solution, the hot water may burn our body. The knife used to cut the pineapple is very sharp and may cut our fingers. 2Wear a pair of thick gloves when handling hot water.

Handle the knife with care.

Write an experimental report (p. 1-4)

Objective
To investigate the effect of fresh pineapple on the setting of jelly.

Hypothesis
It is the fresh pineapple that causes the jelly to remain in liquid form.

Apparatus and materials
|1 electronic balance |2 glass rods | |1 refrigerator |1 knife | |2 beakers (500 cm3) |fresh pineapple | |1 measuring cylinder (100 cm3) |hot water | |2 plastic containers |jelly powder |

Procedure
1Cut a fresh pineapple into small pieces.
2Add 50 g of jelly powder and 200 cm3 of hot water to a beaker. Stir the mixture with a glass rod until all the jelly powders dissolve. 3Pour 100 cm3 of jelly solution into two containers respectively. Leave the jelly solutions at room temperature for one hour. 4Put the small pieces of fresh pineapple into one of the containers. Then, refrigerate two containers overnight. 5Observe any changes of jelly solutions in the two containers on the next day.

Results
The jelly without fresh pineapple set.
The jelly with fresh pineapple does not set.

Analysis and discussion
1It is used to confirm that the presence of fresh pineapple is the only factor that prevents the jelly from setting. 2(Answer varies with the design.)

Conclusion
The presence of fresh pineapple prevents the jelly from setting.

Ch 2The...
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