1. A student performed an experiment to compare the energy content of dry broad beans and dry soybeans.
The student followed the method below.

a. Explain why the dry beans were crushed in step 2 of the experimental method. 2 marks
Solution
b. Identify the dependent variable in this experiment. 1 mark
Solution
c. Identify one step in the experimental procedure that is designed to manage safety hazards. Explain how this step reduces the risks associated with the experiment. 2 marks
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d. When the experiment was undertaken with 1.11 g of dry broad-bean powder, the following results were obtained.

Use the experimental results to calculate the energy content of the dry broad bean in kJ /g. 4 marks

Solution

e. The typical nutrition content of dry soybeans is provided in the table below.

i. Use the nutrition information from the table to calculate the heat of combustion of a typical dry soybean in kJ /g. 2 marks
When the experiment was performed with a dry soybean, the heat of combustion was found to be 35 kJ /g.

Solution

ii. Suggest an experimental error that could have caused the experimental value to be different to the heat of combustion of a typical dry soybean. Explain how this error could have caused thedifference between the experimental result and the expected result. 2 marks

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f. Suggest one improvement to the experimental method using the apparatus and method shown above that would produce more accurate results. Explain how this improvement would improve the
accuracy of the results. 2 marks

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g. Write a valid conclusion for the experiment based on the experimental results. 1 mark

Solution

A student investigated the viscosity of several biofuels.
The flow rate of each biofuel through a narrow glass tube was measured. The results are presented in the tables below.

Table 1: Flow rate (mL /min) of biodiesels produced using sodium hydroxide, NaOH(aq), catalyst

Table 2: Flow rate (mL /min) of biodiesels produced using potassium hydroxide, KOH(aq), catalyst

2. How many independent variables are there in this investigation?
A. 1
B. 3
C. 4
D. 6
3. Select the most valid conclusion that can be drawn from the student’s results presented in Table 1 and Table 2.

A. Biodiesels made from sunflower oil have a higher viscosity than biodiesels made from canola oil.
B. Biodiesels made from methanol have a lower viscosity than biodiesels made from ethanol.
C. Biodiesels are unsuitable for use in cold climates because they have a higher viscosity than petrodiesels.
D. Biodiesels made using NaOH(aq) catalyst have a lower viscosity than biodiesels made using KOH(aq) catalyst.

Solution