IB myp 4-5 physics – Practice Questions- All Topics
Topic :Heat,Light and Sound- Condensation and Evaporation
Topic :Heat– Weightage : 21 %
All Questions for Topic : Condensation and Evaporation,Pressure,Thermal Physics,Heat Transfer
Question (21 marks)
The paragraph is about , how the particles in a liquid leave the surface and become gas particles when the liquid evaporates.
Water can exist as both a liquid and a gas commonly known as water vapour. The mist we often see at the top of a hot cup of tea is not water vapour or steam, as water is invisible, but tiny droplets of condensed water.
To see water vapour we must leave the large-scale world we are familiar with and view the surface of the liquid at the microscopic scale.
If we could zoom in, one model of particle physics tells us this is what we would see at the surface of the water.
Evaporation takes place when one of the particles in the liquid escapes the liquid and enters the gas above the surface.
Over time all of the particles in the liquid will escape in this way, leaving behind an empty container.
Many different factors affect the rate at which a liquid evaporates. You have been asked to investigate the effect that surface area has on the mass of liquid evaporated in an hour.
Question a (1 mark)
State the question that could be answered in this scientific investigation.
▶️Answer/Explanation
Ans:
How does the surface area of a liquid affect the mass of liquid evaporated in an hour?
Question b (3 mark)
If $0.25 \mathrm{~g}$ of water evaporates from a container in 12 minutes, calculate the rate of evaporation. Give your answer in $\mathrm{g} \mathrm{h}^{-1}$.
▶️Answer/Explanation
Ans:
To calculate the rate of evaporation, we need to convert the given time of 12 minutes to hours and then determine how much water evaporates in one hour.
First, let’s convert the time from minutes to hours:
12 minutes $\div$ 60 minutes $/$ hour $=0.2$ hours
Now, we can calculate the rate of evaporation:
Rate of evaporation $=$ (Amount of water evaporated $) \div$ (Time in hours $)$
Rate of evaporation $=0.25 \mathrm{~g} \div 0.2$ hours $=1.25 \mathrm{~g} / \mathrm{h}$
Therefore, the rate of evaporation is $1.25 \mathrm{~g} / \mathrm{h}$.
Question c (3 mark)
Formulate and explain the hypothesis that this question would test.
▶️Answer/Explanation
Ans:
The hypothesis that could be tested based on the given question is:
“An increase in the surface area of a liquid will result in a higher rate of evaporation, leading to a greater mass of liquid evaporated in a given time period.”
Explanation:
The hypothesis suggests that there is a relationship between the surface area of a liquid and the rate of evaporation. It proposes that as the surface area of the liquid increases, more particles at the surface will have the opportunity to escape and enter the gas phase, resulting in a higher rate of evaporation. Consequently, this higher rate of evaporation would lead to a greater mass of liquid evaporated within a specific time frame.
By conducting experiments with different surface areas while keeping other factors constant (e.g., temperature, humidity, etc.), scientists can test this hypothesis. They can measure and compare the masses of liquid evaporated in a fixed time period for different surface areas. If the hypothesis holds true, they would expect to observe a positive correlation between the surface area of the liquid and the mass of liquid evaporated, supporting the idea that an increased surface area enhances the rate of evaporation.