Question 1

A kettle containing water is heated on a stove as shown in the first image. Which of the following best describes the energy flow diagram for the water as it is heated from 10°C to 100°C, but before it boils?

Accepted Answer

The thermal energy ($$E_{th}) $$increases, but the phase energy ($$E_{ph}) $$remains constant.

Question 2

When water at 100°C is boiling, what happens to the temperature and the energy flow diagram as heat continues to be added?

Accepted Answer

The temperature remains constant while the phase energy ($$E_{ph}) $$increases.

Question 3

Which equation correctly describes the heat required to raise the temperature of a mass $$m of $$water from $$T_i to$$ $$T_f ($$with no phase change)?

Accepted Answer

$$Q = mc\Delta T$$

Question 4

A 0.5 kg sample of water at 10°C is heated to 100°C and then completely boiled away. Which set of equations would you use to calculate the total heat required?

Accepted Answer

$$Q_{total} = mc\Delta T + mL_v$$

Question 5

During a calorimetry experiment, a hot piece of copper is placed in cooler water. Which of the following best describes the energy flow diagrams for the two substances?

Accepted Answer

The water gains thermal energy while the copper loses thermal energy.

Question 6

Which equation expresses conservation of energy for a calorimetry problem involving water and copper, assuming no heat loss to the environment?

Accepted Answer

$$Q_{water} + Q_{copper} = 0$$

Question 7

A 0.2 kg sample of water at 22°C is placed in a freezer at -18°C. How many thermodynamic processes are involved in cooling the water to ice at -18°C?

Accepted Answer

Three: cooling water to 0°C, freezing at 0°C, cooling ice to -18°C.

Question 8

Which of the following best describes the temperature vs. heat transfer ($$T vs$$. $$Q) $$graph for water as it is heated from ice at -20°C to steam at 100°C?

Accepted Answer

The graph has sloped regions for temperature changes and flat regions for phase changes.

Question 9

Which of the following statements about specific heat is correct?

Accepted Answer

The specific heat is the amount of heat required to raise the temperature of 1 kg of a substance by 1 K.

Question 10

In the context of thermal expansion, which equation describes the change in length $$\Delta L of a $$rod of initial length $$L_{initial}$$ when its temperature changes by $$\Delta T$$?

Accepted Answer

$$\Delta L = \alpha L_{initial} \Delta T$$

Question 11

A bi-metallic strip is made of brass and steel. When heated, which way will the strip bend?

Accepted Answer

Toward the steel, because brass expands more than steel.

Question 12

Which of the following best explains why an alcohol thermometer works when the air temperature increases?

Accepted Answer

The alcohol expands more than the glass, causing the liquid level to rise.

Question 13

In a Galileo thermometer, what happens to the density of the liquid in the column as the temperature increases?

Accepted Answer

The density decreases due to thermal expansion.

Question 14

Which of the following is true about the densities of the bulbs in a Galileo thermometer?

Accepted Answer

The bulb labeled with the greatest temperature has the smallest density.

Question 15

Which equation describes the rate of heat transfer by conduction through a material of area $$A$$, thickness $$L$$, and thermal conductivity $$k$$, with a temperature difference $$\Delta T$$?

Accepted Answer

$$\frac{Q}{\Delta t} = \frac{kA\Delta T}{L}$$

Question 16

Why does an ice cube melt faster on an aluminum block than on a wood block, even if both are at the same temperature?

Accepted Answer

Aluminum has a much higher thermal conductivity than wood.

Question 17

Which of the following best describes heat transfer by convection?

Accepted Answer

Transfer of thermal energy by the movement of a fluid (liquid or gas).

Question 18

Which equation describes the rate of heat transfer by radiation from an object with surface area $$A$$, temperature $$T$$, and emissivity $$e$$?

Accepted Answer

$$P = e\sigma A T^4$

Question 19

Why do infrared thermometers not accurately measure the temperature of shiny substances like polished metals?

Accepted Answer

Shiny substances have low emissivity and emit less infrared radiation.

Thermal Properties of Matter, Calorimetry, and Simple Harmonic Motion

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