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Q1-3. These questions are about the pressure of air inside a bike tyre:
1. Which of these sentences best explains the change in pressure if the tyre is heated?
2. Which of these rows describes the change in pressure and particle speed if the temperature is kept constant, but more air is pumped into the tyre?
3. When a cyclist sits on the bike, the tyre is compressed. Assuming the temperature remains constant, how does this compression change the volume of the tyre and the pressure in the tyre?
4. As any gas is cooled, the particles slow down. At what temperature do the particles have the least kinetic energy?
5. What is -173 °C in kelvin?
6. What is 400 K in °C?
7. The syringe is pulled out slowly, increasing the volume to 75 cm3 whilst the temperature remains constant.
What is the new pressure in the gas?
8. At what volume would the pressure be 125 kPa?
9. What is the pressure in pascals when the bottle is left in strong sunlight and the temperature reaches 350 K?
10. At what temperature will the pressure be 9 x104 Pa?
Question 1:
When a tyre is heated:
The number of air particles inside doesn’t change (unless it’s leaking or more air is added).
The particles move faster (higher kinetic energy).
Faster movement means they hit the tyre walls harder and more often (since speed increases the collision rate with the walls).
This increases the pressure (from the ideal gas law: P∝T at constant volume).
Correct explanation: B — “The pressure increases because the particles hit the sides harder and more often.”
*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret. Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.
Question 2:
Let’s break this down:
Temperature is constant → average particle speed stays the same.
More air is pumped in → number of particles increases.
Pressure comes from particles hitting the walls. With more particles at the same speed, collisions with the walls happen more often (per unit time), so pressure increases.
That matches: Pressure increases, Particle speed stays the same → option A.
Question 3:
Let’s reason through:
Cyclist sits on bike → weight compresses the tyre → volume decreases.
Temperature constant.
According to Boyle’s law (P×V=constant at constant T), if volume decreases, pressure increases.
So: Volume decreases, Pressure increases → option D.
Question 4:
The particles have the least kinetic energy when they are as cold as possible — that is, at absolute zero.
Absolute zero is:
At this temperature, particle motion (in classical terms) has the minimum kinetic energy.
So the correct choice is: C) -273 °C
Question 5:
To convert from Celsius to kelvin:
Here:
So the answer is A) 100 K.
Question 6:
To convert from kelvin to Celsius:
So the answer is C) 127 °C.
Question 7:
We can use Boyle’s Law at constant temperature:
P1V1=P2V2
Given:
P1=100 kPa, V1=30 cm3, V2=75 cm3
100×30=P2×75
3000=P2×75
P2=3000/75=40 kPa
Correct answer: D) 40 kPa.
Question 8:
We continue with Boyle's Law from the previous setup:
With P1=100 kPa, V1=30 cm3, and P2=125 kPa:
100×30=125×V2
3000=125×V2
V2=3000/125=24 cm3
The correct answer is B) 24 cm³.
Question 9:
We can use the pressure law (Gay-Lussac’s law) for a gas at constant volume:
P1/T1=P2/T2
P1=1×105 Pa, T1=300 K, T2=350 K
P2=P1×T2 / T1
P2=1×105×350/300
P2=1×105×1.167
P2≈1.167×105 Pa
This is closest to 1.2×105 Pa in the options given.
Answer: A) 1.2×105 Pa.
Question 10:
We use the pressure law again at constant volume:
P1=1×105 Pa, T1=300 K ,P2=9×104 Pa
T2=T1×P2 / P1
T2=300×9×104 / 1×105
T2 = 270 K
Now convert to Celsius:
Correct answer: D) -3 °C.