A student investigated the insulating properties of different materials.
Figure 4 shows some of the equipment used by the student
This is the method used:
1. Wrap insulating material around the can.
2. Put a fixed volume of boiling water in the can.
3. Place the lid on the top of the can.
4. Measure the time taken for the temperature of the water to decrease by a fixed amount.
5. Repeat steps 1–4 using the same thickness of different insulating materials.
i- Identify the independent variable and the dependent variable in this investigation.
[2 marks]
SOLUTION
Take the help of the following flash card.
In the question, it is given that the time taken for the temperature of the water to decrease by a fixed amount has to be measured, meaning thereby time is depending. Whereas, the type of insulating material is the one that can be changed by you, therefore, it is independent variable.
Independent variable: Insulating materials
Dependent variable: Time taken
The student used two different types of thermometer to measure the temperature changes.
Figure 5 shows a reading on each thermometer.
ii- What is the resolution of thermometer B?
[1 mark]
SOLUTION
Take the help of the following flashcard.
Thermometer A is more likely to be misread.
iii- Give one reason why.
[1 mark]
SOLUTION
Parallax error is mostly like to occur .
For one type of insulating material, the temperature of the water decreased from 85.0 °C to 65.0 °C.
The energy transferred from the water was 10.5 kJ.
specific heat capacity of water = 4200 J/kg °C
iv- Calculate the mass of water in the can.
Use the Physics Equations Sheet.
[3 marks]
SOLUTION
or
Table 2 shows the results for two insulating materials.
v- Explain how the results in Table 2 can be used to compare the thermal conductivity of the two materials.
[2 marks]
SOLUTION
At same temperature difference, but in a shorter time means X has a higher thermal conductivity.
Rate of energy transfer of X is higher than Y.
