Edexcel iGCSE Physics (4PH1) 5.1 Units Exam Style Question Paper 1B - New Syllabus
Question
A student wants to determine the density of air using an irregularly-shaped balloon made of metal foil. The balloon has a label stating that the volume of the balloon when full is \(490\,\mathrm{cm^3}\). This is part of the student’s method.
Step 1 measure the mass of the empty balloon
Step 2 fill the balloon with air
Step 3 measure the mass of the full balloon
Step 4 subtract the mass of the empty balloon from the mass of the full balloon.
(a)(i) Name the equipment the student could use to measure the mass of the balloon.
(ii) Suggest how the student could improve the reliability of their data.
(b) The table shows the student’s results.
Calculate the density of air to 2 significant figures. Give the unit.
(c) Describe how the volume of the balloon full of air could be measured using a large beaker and some water. You may use a diagram to help your answer.
Syllabus Topic Codes (Edexcel International GCSE Physics 4PH1):
• 5.4: Core Practical: Density Measurements — parts (a) and (c)
▶️ Answer/Explanation
(a)(i) Equipment for measuring mass [1 mark]
The student could use a balance to measure the mass of the balloon.
(a)(ii) Improving reliability [1 mark]
The student should repeat the measurements and calculate a mean. Any anomalous result should be identified and, where appropriate, excluded from the calculation.
(b) Density of air [4 marks]
First calculate the mass of the air by subtracting the mass of the empty balloon from the mass of the full balloon:
\(\mathrm{mass\ of\ air}=15.61-15.00\)
\(\mathrm{mass\ of\ air}=0.61\,\mathrm{g}\)
Use the density equation:
\(\rho=\dfrac{m}{V}\)
Substitute \(m=0.61\,\mathrm{g}\) and \(V=490\,\mathrm{cm^3}\):
\(\rho=\dfrac{0.61}{490}\)
\(\rho=0.001244\ldots\,\mathrm{g\,cm^{-3}}\)
To 2 significant figures:
Therefore: \(\boxed{\rho=0.0012\,\mathrm{g\,cm^{-3}}}\)
(c) Measuring the volume using water [3 marks]
The volume can be measured using the water displacement method.
- Measure and record the original volume of water in the large beaker.
- Fully submerge the inflated balloon in the water, ensuring that it is completely underwater.
- Measure the new volume of water and subtract the original volume from the new volume. The difference is the volume of the balloon.
Thus:
\(\mathrm{volume\ of\ balloon}=\mathrm{final\ water\ volume}-\mathrm{initial\ water\ volume}\)
Questions
The drawing shows a camel and a person in a desert.
(a) Describe a method you could use to find the pressure a person exerts on the ground when standing on two feet. (4)
(b) The total area of contact of the camel’s feet with the ground is \(1300\,\mathrm{cm^2}\). The mass of the camel is \(660\,\mathrm{kg}\). Calculate the pressure this camel exerts on the ground. (3)
Syllabus Topic Code (Edexcel International GCSE Physics 4PH1):
▶️ Answer/Explanation
(a) Method to determine pressure [4 marks]
- Measure the total area of contact of the person’s two feet with the ground.
- One method is to draw around the feet on squared or grid paper and use the grid to determine the total area.
- Measure the person’s mass using a balance or scales, then calculate their weight using \(W=mg\).
- Calculate the pressure using \(P=\dfrac{F}{A}\), where \(F\) is the weight of the person and \(A\) is the total contact area.
Thus:
\(\boxed{P=\dfrac{F}{A}}\)
(b) Pressure exerted by the camel [3 marks]
1. Calculate the weight of the camel:
\(W=mg\)
\(W=660\times10\)
\(W=6600\,\mathrm{N}\)
2. Calculate the pressure:
\(P=\dfrac{F}{A}\)
\(P=\dfrac{6600}{1300}\)
\(P\approx5.1\,\mathrm{N\,cm^{-2}}\)
\(\boxed{P\approx5.1\,\mathrm{N\,cm^{-2}}}\)
The area is given in \(\mathrm{cm^2}\), so the pressure is appropriately expressed in \(\mathrm{N\,cm^{-2}}\). If expressed in SI units, the area would first need to be converted to \(\mathrm{m^2}\).