Q: Which equation correctly expresses the energy released by a hot object cooling down?

$$q = m_{\text{hot}} C \Delta T_{\text{hot}}$$

Q: Given 90.0 grams of hot water at $$90.0^\circ\mathrm{C}$$ and 10.0 grams of cold water at $$10.0^\circ\mathrm{C}$$, what is the correct expression for the energy absorbed by the cold water?

$$q = m_{\text{cold}} C \Delta T_{\text{cold}}$$

Q: If $$q_{\text{released}} = -q_{\text{absorbed}}$$, which equation would you use to solve for the final temperature $$x$$ when mixing two water samples?

$$m_{\text{hot}} C (T_{\text{final}} - T_{\text{hot}}) = -m_{\text{cold}} C (T_{\text{final}} - T_{\text{cold}})$$

Q: A 175 g piece of aluminum at $$100.0^\circ\mathrm{C} is $$placed in 40.0 mL of water at $$0.0^\circ\mathrm{C}. If $$the specific heat of aluminum is $$0.900 \ \mathrm{J/g\cdot ^\circ C}$$, which of the following is the correct setup to find the final temperature $$x$$?

$$m_{\text{Al}} C_{\text{Al}} (x - 100.0) = -m$$_{\text{H}$$_2\text{O}} C$$_{\text{H}$$_2\text{O}} (x - 0.0)$$

Question 1

When two objects at different temperatures are placed in contact, what is the direction of heat flow?

Accepted Answer

From the object with higher temperature to the object with lower temperature.

Question 2

Which of the following best describes thermal equilibrium?

Accepted Answer

Both objects reach the same temperature and there is no net heat flow between them.

Question 3

At the molecular level, what happens when a hot object is placed in contact with a cold object?

Accepted Answer

Faster-moving particles in the hot object collide with slower-moving particles in the cold object, transferring energy.

Question 4

Which equation correctly expresses the energy released by a hot object cooling down?

Accepted Answer

$$q = m_{	ext{hot}} C \Delta T_{	ext{hot}}$$

Question 5

Given 90.0 grams of hot water at $$90.0^\circ\mathrm{C}$$ and 10.0 grams of cold water at $$10.0^\circ\mathrm{C}$$, what is the correct expression for the energy absorbed by the cold water?

Accepted Answer

$$q = m_{	ext{cold}} C \Delta T_{	ext{cold}}$$

Question 6

If $$q_{	ext{released}} = -q_{	ext{absorbed}}$$, which equation would you use to solve for the final temperature $$x$$ when mixing two water samples?

Accepted Answer

$$m_{	ext{hot}} C (T_{	ext{final}} - T_{	ext{hot}}) = -m_{	ext{cold}} C (T_{	ext{final}} - T_{	ext{cold}})$$

Question 7

A 175 g piece of aluminum at $$100.0^\circ\mathrm{C} is $$placed in 40.0 mL of water at $$0.0^\circ\mathrm{C}. If $$the specific heat of aluminum is $$0.900 \ \mathrm{J/g\cdot ^\circ C}$$, which of the following is the correct setup to find the final temperature $$x$$?

Accepted Answer

$$m_{	ext{Al}} C_{	ext{Al}} (x - 100.0) = -m$$_{	ext{H}$$_2	ext{O}} C$$_{	ext{H}$$_2	ext{O}} (x - 0.0)$$

Question 8

Which of the following statements about the molecular motion in the image is correct as thermal equilibrium is approached?

Accepted Answer

The average kinetic energy of particles in both blocks becomes equal.

Question 9

Why is it important to use an insulated cup in calorimetry experiments like the aluminum and water example?

Accepted Answer

To prevent heat exchange with the surroundings, ensuring all energy transfer occurs between the substances measured.

Question 10

If 90.0 g of hot water at $$90.0^\circ\mathrm{C} is $$mixed with 10.0 g of cold water at $$10.0^\circ\mathrm{C}$$, and the specific heat capacity of water is $$4.184 \ \mathrm{J/g\cdot ^\circ C}$$, which of the following best describes the final temperature?

Accepted Answer

It will be closer to $$90.0^\circ\mathrm{C}$$ because there is much more hot water than cold water.

Question 11

Which of the following is a correct statement about the conservation of energy in thermal energy transfer?

Accepted Answer

The total energy lost by the hot object equals the total energy gained by the cold object.

Question 12

A student mixes 50.0 g of copper at $$80.0^\circ\mathrm{C}$$ with 100.0 g of water at $$20.0^\circ\mathrm{C} in an $$insulated container. The specific heat of copper is $$0.385 \ \mathrm{J/g\cdot ^\circ C}$$ and for water is $$4.184 \ \mathrm{J/g\cdot ^\circ C}. $$Which equation should be used to solve for the final temperature $$x$$?

Accepted Answer

$$m_{	ext{Cu}} C_{	ext{Cu}} (x - 80.0) = -m$$_{	ext{H}$$_2	ext{O}} C$$_{	ext{H}$$_2	ext{O}} (x - 20.0)$$

Question 13

Which real-life scenario best illustrates the concept of thermal equilibrium?

Accepted Answer

A metal spoon left in a cup of hot tea eventually becomes the same temperature as the tea.

Question 14

Which of the following is NOT a correct assumption when applying the calorimetry equations in a closed system?

Accepted Answer

There is significant heat loss to the surroundings.

Thermal Energy Transfers and Thermal Equilibrium

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