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Solving Exercise SBT Physics Grade 6 Exercise 18: Thermal Expansion of Solids
Exercise 18.1 Page 57 Physics Exercise Book (SBT) Grade 6
When heating a solid object, which of the following phenomena occurs?
A. The mass of the object increases.
B. The mass of the object decreases.
C. The density of the object increases.
D. The density of the object decreases
* Answer:
Choose D
* Explanation:
When a solid object is heated, its mass remains constant while its volume increases, leading to a decrease in its density.
Exercise 18.2 on page 57 of the Physics Exercise Book (SBT) Grade 6
A glass bottle is sealed with a glass stopper. The stopper is stuck. How should you open the stopper from the following options?
A. Heat the stopper. B. Heat the neck of the bottle.
* Answer:
Choose B
* Solution:
A glass bottle is sealed with a glass stopper. If the stopper is stuck, we can open it by heating the neck of the bottle. When heated, the neck expands, loosening the stopper, allowing us to open it.
Exercise 18.3 on page 57 of the Physics Exercise Book (SBT) Grade 6
Based on the expansion coefficient table, calculate the millimeters of various 1-meter-long bars made of different substances when the temperature increases by 1°C to answer the following questions:
Thủy tinh chịu lửa | Thủy tinh thường | Hợp kim pla-ti-ni | Sắt | Nhôm | Đồng |
3 | Từ 8 đến 9 | 9 | 12 | 22 | 29 |
1. Which material should be used as the electrical conductor passing through the neck of an ordinary glass bulb to ensure the joint remains sealed?
A. Iron. B. Copper.
C. Platinum alloy. D. Aluminum.
* Answer:
Choose C
* Explanation:
One must use a platinum alloy conductor passing through the neck of an ordinary glass bulb to ensure the joint remains sealed, because the expansion of platinum and ordinary glass is equivalent.
2. Why does a glass cup made of heat-resistant glass not break when hot water is poured into it, while a cup made of ordinary glass is more likely to break when hot water is poured into it?
Insightful Solution:
Fire-resistant glass, with its minimal expansion capacity, ensures that the inner layer of the cup experiences minimal expansion when in contact with hot water, hence reducing the risk of breakage.
Exercise 18.4 on page 57 of the Physics Exercise Book (PEB) for Grade 6
Figure 18.1 depicts the experimental apparatus validating the phenomenon of elongation in solid objects. The horizontal bar snugly fits into the measuring device when both are at room temperature (Fig. 18.1).
a) Why is it impossible to insert the heated bar into the measuring device?
b) Propose a method to insert the heated bar into the measuring device without cooling it down.
Insightful Solution:
a) When heating the horizontal bar, it becomes impossible to insert it into the measuring device due to its expansion.
b) To insert the heated horizontal bar into the measuring device without cooling it down, both the measuring device and the bar can be heated simultaneously.
Exercise 18.5 on page 58 of the Physics Exercise Book (PEB) for Grade 6
When solid objects are cooled, their density increases because
A. the mass of the object increases while its volume decreases.
B. the mass of the object decreases while its volume decreases.
C. the mass of the object remains constant while its volume decreases.
D. the mass of the object increases while its volume remains constant.
Answer:
Option C
Explanation:
When solid objects are cooled, their mass remains constant while their volume decreases. Thus, the density of the object increases.
Exercise 18.6 on page 58 of the Physics Exercise Book (PEB) for Grade 6
When heating the metal ring depicted in Figure 18.2, the following changes occur:
A. Radius R1 increases, radius R2 decreases.
B. Radius R2 increases, radius R1 decreases.
C. Length d decreases.
D. Both R1, R2, and d increase.
Answer:
Option D
Explanation:
When heating the metal ring depicted in Figure 18.2, both R1, R2, and d increase.
Exercise 18.7 on page 58 of the Physics Exercise Book (PEB) for Grade 6
When temperature changes, reinforced concrete columns do not crack because
A. concrete and steel do not expand due to heat.
B. concrete expands more than steel due to heat.
C. concrete expands less than steel due to heat.
D. both concrete and steel expand equally due to heat.
Answer:
Option D
Explanation:
When temperature changes, reinforced concrete columns do not crack because concrete and steel expand equally due to heat.
Exercise 18.8 on page 58 of the Physics Exercise Book (PEB) for Grade 6
Three rods, one made of copper, one made of aluminum, and one made of iron, have equal lengths at 0°C. When the temperature of the three rods increases to 100°C, then
A. the lengths of the three rods remain equal.
B. the length of the aluminum rod is the smallest.
C. the length of the iron rod is the smallest.
D. the length of the copper rod is the smallest.
Answer:
Option C.
* Explanation:
If three rods, one made of copper, one made of aluminum, and one made of iron, have equal lengths at 0°C. When the temperature of the three rods increases to 100°C, then the length of the iron rod is the smallest because iron expands the least due to heat.
Exercise 18.9 on page 58 of the Physics Exercise Book (PEB) for Grade 6
A aluminum sphere is stuck inside an iron ring. To separate the sphere from the ring, a student heats both the sphere and the ring. Will the student be able to separate the sphere from the ring? Why?
* Solution Guide:
Cannot separate because the aluminum sphere expands more than iron due to heat, so when heated, it becomes even more tightly squeezed into the iron ring.
Exercise 18.10 on page 58 of the Physics Exercise Book (PEB) for Grade 6
There are two glass cups stuck together. A student intends to use hot water and ice to separate the two cups. What should the student do?
* Solution Guide:
The student should proceed as follows: pour ice water into the inner cup, immerse the outer cup in hot water. By doing so, the inner cup contracts, while the outer cup expands, causing them to separate.
Exercise 18.11 on page 58 of the Physics Exercise Book (PEB) for Grade 6
When the temperature increases by 1°C, the length of a copper wire, originally 1m long, increases by 0.017mm. If the increase in length due to thermal expansion is proportional to the original length and the temperature increase of the object, what will be the length of a copper wire, originally 50m long at 20°C, at 40°C?
* Solution Guide:
The length of the wire at 40°C is:
l = l0 + l0(40 -20). 0.017.10^-3 = 50 + 50.20.0.017.10^-3 = 50.017m
