Thermal Energy: Understanding Heat and Energy Changes

What is the specific heat content of a substance?

• The amount of heat required to change the temperature of 1 kg of the substance by 1°C.

• The amount of heat required to melt 1 kg of the substance.

• The amount of heat required to vaporize 1 kg of the substance.

• The amount of heat required to change the temperature of 1 g of the substance by 1°C.

Answer explanation

The specific heat content of a substance is defined as the amount of heat required to change the temperature of 1 kg of the substance by 1°C, making the first choice the correct answer.

Which formula is used to calculate the heat content of a substance?

Answer explanation

The correct formula to calculate the heat content of a substance is Q = mCT, where Q is the heat energy, m is the mass, C is the specific heat capacity, and T is the change in temperature.

• Mass of the substance

• Temperature change

• Specific heat capacity

• Heat content

Answer explanation

In the formula Q = mCT, the symbol C represents the specific heat capacity of the substance. It quantifies the amount of heat required to change the temperature of a unit mass of the substance by one degree Celsius.

How do you calculate the energy input or released using specific heat content?

Answer explanation

The correct formula to calculate energy input or released using specific heat is Q = mCT, where Q is the heat energy, m is the mass, C is the specific heat capacity, and T is the temperature change.

What is latent heat?

• The heat required to change the temperature of a substance.

• The heat required to change the state of a substance without changing its temperature.

• The heat required to increase the kinetic energy of a substance.

• The heat required to decrease the potential energy of a substance.

Answer explanation

Latent heat is the energy needed to change a substance's state, such as from solid to liquid, without altering its temperature. This distinguishes it from heat that changes temperature or kinetic energy.

Which formula is used to calculate latent heat?

Answer explanation

The formula for calculating latent heat is Q = ml, where Q is the heat absorbed or released, m is the mass, and l is the latent heat. This formula specifically applies to phase changes without temperature change.

What is the distinction between latent heat of fusion and latent heat of vaporization?

• Fusion involves melting, vaporization involves freezing.

• Fusion involves freezing, vaporization involves melting.

• Fusion involves melting, vaporization involves boiling.

• Fusion involves boiling, vaporization involves melting.

Answer explanation

The latent heat of fusion refers to the energy required for a substance to melt (solid to liquid), while the latent heat of vaporization refers to the energy needed for boiling (liquid to gas). Thus, fusion involves melting, and vaporization involves boiling.

What type of energy is involved in latent heat?

• Kinetic energy only

• Potential energy only

• Both kinetic and potential energy

• Neither kinetic nor potential energy

Answer explanation

Latent heat involves the energy required to change a substance's state (e.g., melting or boiling) without changing its temperature. This energy is stored as potential energy, making 'Potential energy only' the correct choice.

During the latent heat part of a heating curve, what happens to the temperature of the substance?

• It increases.

• It decreases.

• It remains constant.

• It fluctuates.

Answer explanation

During the latent heat phase, the substance absorbs heat to change its state without a temperature increase. Therefore, the temperature remains constant while the phase change occurs.

How is the energy added to a substance during the latent heat part of a heating curve calculated?

Answer explanation

The energy added during the latent heat phase is calculated using the formula Q = ml, where m is the mass and l is the latent heat. This formula accounts for the energy required for phase changes without temperature change.