Grade 10 physics – Temperature and Thermal Expansion Quiz
1. Which temperature scale has its zero point at absolute zero and is commonly used in physics calculations?
The Kelvin scale sets 0 K at absolute zero (−273.15 °C) and is used in physics because it is an absolute thermodynamic temperature scale.
2. What is the Kelvin temperature equivalent of 27 °C?
Convert °C to K by adding 273.15: 27 + 273.15 = 300.15 K.
3. Which statement best describes thermal equilibrium between two bodies?
Thermal equilibrium means equal temperatures and no net heat transfer between the bodies.
4. A metal rod of length 2.0 m has coefficient of linear expansion 1.2 × 10^-5 K^-1. What is its increase in length when heated by 50 °C?
Use ΔL = α L ΔT = (1.2×10^-5)(2.0)(50) = 1.2×10^-3 m = 0.0012 m.
5. Which of the following materials will expand most for the same rise in temperature per unit length?
A larger coefficient of linear expansion α means more expansion per unit length for the same temperature rise; aluminium has the largest α listed.
6. A brass lid on a jar is difficult to remove. Which practical method based on thermal expansion will help remove it?
Heating the metal lid causes it to expand slightly, increasing its diameter and making it easier to remove; cooling would make it tighter.
7. If a steel railway line is laid without gaps and the temperature rises significantly, what is the likely danger?
When rails are constrained and heat causes them to expand, the lack of room for expansion can cause buckling and bending.
8. The coefficient of volume expansion β of a solid is approximately related to its coefficient of linear expansion α by which relation?
For isotropic solids small linear expansions in three directions lead to β ≈ 3α for volume expansion coefficient.
9. A mercury-in-glass thermometer is unsuitable for measuring very low temperatures below −39 °C because:
Mercury solidifies (freezes) at about −38.83 °C, so mercury thermometers cannot read temperatures below this point reliably.
10. Which instrument determines temperature by the thermal expansion of a bimetallic strip and is commonly used in thermostats?
A bimetallic strip of two metals with different α values bends when heated; this bending is used in thermostats to switch heating/cooling devices.
11. Which of the following correctly describes absolute zero in Celsius?
Absolute zero, the lowest possible temperature, corresponds to 0 K which equals −273.15 °C.
12. When a liquid is heated at constant pressure, which kind of expansion primarily takes place?
Liquids cannot be described by a single linear dimension; they expand by increasing volume when heated at constant pressure.
13. A 0.5 m length of copper (α = 1.7×10^-5 K^-1) is heated from 20 °C to 70 °C. What is the change in length?
ΔL = αLΔT = (1.7×10^-5)(0.5)(50) = 4.25×10^-4 m = 0.000425 m.
14. Why are expansion gaps left between concrete slabs or railway tracks in Kenya’s roads and railways?
Gaps accommodate expansion when temperature rises; without them, thermal stresses can cause cracking or buckling.
15. Which of these substances shows the largest fractional change in volume for the same temperature increase?
Gases have much larger coefficients of volume expansion than solids or liquids, so they expand most for a given temperature rise when allowed to change volume.
16. Which relation correctly gives the change in length ΔL of a rod when its temperature changes by ΔT?
The linear expansion formula is ΔL = α L ΔT, where α is the coefficient of linear expansion.
17. A metal ring fits tightly over a metal cylinder. To remove the ring without damage, one should:
Cooling the ring reduces its diameter slightly due to contraction, making it loose; heating the cylinder would make the cylinder larger and make removal harder.
18. If two rods of different metals are rigidly joined end-to-end and the temperature increases, what happens if they expand differently but cannot move?
Constrained rods that would like to expand but cannot produce internal thermal stresses due to the mismatch in expansion.
19. Which thermometer is most suitable for measuring very low temperatures in a Kenyan school lab (below −80 °C)?
Mercury freezes near −38.8 °C and standard alcohol thermometers have limits; a properly designed electronic thermistor or low-temperature digital probe is suitable for very low temperatures.
20. Why does heating a sealed metal container increase pressure inside it (if volume cannot change)?
Raising temperature increases the average kinetic energy of molecules, causing more frequent and forceful collisions with the walls and thus higher pressure if volume is fixed.
21. Which of the following is a practical application of differential thermal expansion?
Bimetallic strips exploit different thermal expansions of two metals; they bend with temperature change and are widely used in thermostats.
22. What happens to the density of a metal rod when it is heated (and free to expand)?
Heating increases volume (expansion) while mass is unchanged, so density (mass/volume) decreases.
23. Which temperature is equivalent to 0 K on the Celsius scale?
0 Kelvin is absolute zero, which is −273.15 °C on the Celsius scale.
24. A metal beam 4.0 m long has α = 1.0×10^-5 K^-1. If the beam warms by 40 °C, what is its new length?
ΔL = α L ΔT = (1.0×10^-5)(4.0)(40) = 1.6×10^-3 m, so new length = 4.0 + 0.0016 = 4.0016 m.
25. Why is aluminium used for cooking pots in Kenya despite its relatively large thermal expansion coefficient?
Aluminium is chosen for cookware because it conducts heat well and is light; its thermal expansion is manageable in this use.
26. Which conversion is correct for converting 100 °C to Fahrenheit?
Use F = (9/5)C + 32: (9/5)×100 + 32 = 180 + 32 = 212 °F.