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Solving Exercise SBT Physics Grade 6 Exercise 19: Thermal Expansion of Liquids
Exercise 19.1 on page 59 of Exercise Book (SBT) Physics 6:
Which of the following phenomena will occur when heating a quantity of liquid?
A. The mass of the liquid increases.
B. The weight of the liquid increases.
C. The volume of the liquid increases.
D. Both the mass, weight, and volume increase.
* Answer:
Choose C.
* Solution:
When heating a quantity of liquid, the liquid expands, resulting in an increase in the volume of the liquid.
Exercise 19.2 on page 59 of Exercise Book (SBT) Physics 6:
What phenomenon will occur with the specific gravity of a liquid when heating a quantity of this liquid in a glass container?
A. The specific gravity of the liquid increases.
B. The specific gravity of the liquid decreases.
C. The specific gravity of the liquid remains unchanged.
D. The specific gravity of the liquid initially decreases, then increases.
* Answer:
Choose B
* Explanation:
When heating a quantity of liquid in a glass container, the specific gravity of the liquid decreases because the volume increases while the mass remains constant.
Exercise 19.3 on page 59 of Exercise Book (SBT) Physics 6
Describe the experiment shown in figure 19.1 and explain
* Solution guide:
When heated, initially the water level in the tube drops slightly, then rises above the initial level. Because the glass container contacts the flame first, expanding and causing the liquid in the tube to contract. Then, the water also heats up and expands. Since water expands more than glass, the water level in the tube rises above the initial level.
Exercise 19.4 on page 59 of Exercise Book (SBT) Physics 6:
Why are 20°C usually marked on standard measuring cylinders?
Answer:
Because the volume of the container depends on temperature. The marking of 20°C on the container means that the volume values marked on the container are only accurate at temperatures above. When measuring liquid at temperatures other than 20°C, the measured values are not entirely accurate. However, this error is very small and insignificant for experiments that do not require high precision.
Exercise 19.5 on page 59 of Exercise Book (SBT) Physics 6:
An plans to fill a glass bottle with water, seal it tightly, and put it in the freezer compartment as an ice pack. The compartment is inaccessible to An due to safety reasons. Explain why?
* Solution guide:
As water freezes into ice, its volume increases, which can cause the glass bottle containing water to crack, posing a danger.
Exercise 19.6 on page 60 of Exercise Book (SBT) Physics 6:
Using precise instruments, one can measure the volume of the same amount of benzene (a flammable liquid) at different temperatures.
1. Calculate the volume increase (compared to V0) based on temperature and fill in the table.
Temperature (°C) Volume (cm3) Volume Increase (cm3)
0 V0 = 1000 AV0 =
10 V1 = 1011 AV1 =
20 V2 = 1022 AV2 =
30 V3 = 1033 AV3 =
40 V4 = 1044 AV4 =
2. Redraw figure 19.2 in your notebook, using a plus sign (+) to indicate the volume increase corresponding to temperature (for example, in the figure, the volume increase AV2 corresponds to a temperature of 20°C).
a) Do the plus signs lie on a straight line?
b) Can you use this representation to predict the volume increase at 25°C? How?
* Solution guide:
1. Calculate the volume increase (compared to V0) based on temperature and fill in the table.
Temperature (°C) Volume (cm3) Volume Increase (cm3)
0 V0 = 1000 AV0 = 0
10 V1 = 1011 AV1 = 11cm3
20 V2 = 1022 AV2 = 22cm3
30 V3 = 1033 AV3 = 33cm3
40 V4 = 1044 AV4 = 44cm3
2. Refer to the image below
a) The plus signs lie on a straight line.
b) This representation can be used to predict the volume increase. Approximately 27cm3.
Exercise 19.7 on page 60 of Exercise Book (SBT) Physics 6
A. initially decreases slightly, then rises higher than the original level.
* Answer:
Choose B
* Explanation:
Initially decreases slightly because the container expands but the water does not, then rises higher than the original level because at this point the water expands, and the expansion of the water exceeds that of the container.
Exercise 19.8 on page 61 of Exercise Book (EB) Physics 6
Two spherical containers 1 and 2 shown in figure 19.4 have the same volume and are both filled with water. The glass tubes inserted into the two containers have inner diameters d1 > d2. When the temperature of both containers is increased equally, then
A. the water level in the glass tube of container 1 rises higher than the water level in the glass tube of container 2.
B. the water level in the glass tube of container 2 rises higher than the water level in the glass tube of container 1.
C. The water level in both glass tubes rises equally.
D. The water level in both glass tubes remains unchanged.
* Answer:
Choose B
* Solution:
When the temperature of both containers is increased equally, the water level in the glass tube of container 2 rises higher than the water level in the glass tube of container 1. Because the volumes increase equally but d1 > d2, hence the height h1 <>
Exercise 19.9 on page 61 of Exercise Book (EB) Physics 6
Three spherical containers 1, 2, 3 (Fig. 19.5a) have the same volume, with glass tubes inserted having the same inner diameter. Container 1 is filled with water, container 2 is filled with alcohol, and container 3 is filled with oil. The temperature of the three containers is increased until the liquid levels in the three glass tubes rise to the same level (Fig. 19.5b). At that point
A. the temperatures of the three containers are the same.
B. container 1 has the lowest temperature.
C. container 2 has the lowest temperature.
D. container 3 has the lowest temperature.
Exercise 19.10 on page 61 of Exercise Book (EB) Physics 6
In which of the following cases does water have the highest density?
A. Liquid state, temperature higher than 4°C.
B. Liquid state, temperature equal to 4°C.
C. Solid state, temperature equal to 0°C.
D. Gaseous state, temperature equal to 100°C.
* Solution:
Choose B
* Solution:
Because for the same mass of water, at the liquid state, at a temperature of 4°C, it has the smallest volume, hence the highest density.
Exercise 19.11 on page 62 of Exercise Book (EB) Physics 6
The density of alcohol at 0°C is 800kg/m3. Calculate the density of alcohol at 50°C, knowing that when the temperature increases by 1°C, the volume of alcohol increases by 1/1000 of its volume at 0°C.
* Solution:
Considering 1m3 of alcohol at 0°C has a mass of 800kg
So the volume at 50°C is:
The density of alcohol at 50°C is:
Exercise 19.12 on page 62 of Exercise Book (EB) Physics 6
The tool shown in figure 19.6 is used to measure the thermal expansion of a liquid. At temperature t1°C, the water level in the graduated tube is at position number 0, while at temperature t2°C, the water level is at position number 5. The distance between two consecutive marks on the tube is 1cm³.
a) When the temperature increases from t1°C to t2°C, by how many cm³ does the volume of the liquid increase?
b) Is the measurement result accurate? Why?
*Solution:
a) When the temperature increases from t1°C to t2°C, the volume of the liquid increases by 1cm³.
b) The measurement result is not perfectly accurate because although the water expands, the container also expands, so the actual expansion of the water must be slightly larger.
Exercise 19.13 on page 62 of Exercise Book (EB) Physics 6
Figure 19.7 illustrates an experiment designed to demonstrate the thermal expansion of water.
Answer the following questions based on the figure:
a) In experiment 19.7a, what temperature is the water brought to?
b) In experiment 19.7b, what temperature is the water brought to? How does the volume of water change from experiment 19.7a to experiment 19.7b?
c) In experiment 19.7c, what temperature is the water brought to? How does the volume of water change from experiment 19.7b to experiment 19.7c?
d) What conclusion can be drawn about the thermal expansion of water from the experiments?
* Solution:
a) In experiment 19.7a, the water is brought to a temperature of 0°C.
b) In experiment 19.7b, the water is brought to a temperature of 4°C. The volume of water decreases from experiment 19.7a to experiment 19.7b.
c) In experiment 19.7c, the water is brought to a temperature of 7°C. The volume of water increases from experiment 19.7b to experiment 19.7c.
d) The conclusion drawn from the experiments is: The thermal expansion of water is peculiar. From 0°C to 4°C, the volume of water decreases as temperature increases. At 4°C, the volume of water decreases to a minimum. Beyond 4°C, the volume of water increases with temperature.
