Question 1

Explain how the specific heats of materials are measured using the technique of calorimetry.

Accepted Answer

The specific heat of a substance can be determined by measuring the masses and temperature changes of the objects involved. Typically a substance of known mass and temperature is put into a quantity of water in a calorimeter. The water is at a different temperature from that of the substance, usually a lower one. The principle of the conservation of energy is then applied to determine the substance's specific heat. This method is called the method of mixtures.

Question 2

Why do you suppose water has been such a popular heat transfer material (steam heat, hot water systems, etc)?

Accepted Answer

It is readily available, but more importantly, it has a relatively large heat capacity and latent heat values. Hence, it can store large quantities of heat to be transferred elsewhere.

Question 3

Glass has more than three times larger thermal conductivity than air. Yet glass-wool (glass fibers and air) air spaces. Why is glass-wool better although glass has larger conductivity than air?

Accepted Answer

Convection is very important, and the glass fibers reduce the convecting air currents.

Question 4

It was once thought that a "black hole" absorbed all the radiation falling upon it and radiated none. If this were true, what would one infer the temperature of a black hole to be? Actually Stephen Hawking discovered that black holes have a VERY small probability of radiating. Modifying your first answer, would you now infer a large or small temperature for a black hole.?

Accepted Answer

The answer of It was once thought that a "black...

Question 5

The mechanical equivalent of heat was first determined by

Accepted Answer

Count Rumford was the first to determine the mechanical equivalent of heat.

Question 6

Which of the following represents the "Mechanical Equivalent of Heat"?

Accepted Answer

The "Mechanical Equivalent of Heat" is a concept that relates the amount of mechanical energy (in joules) to the amount of heat energy (in calories). Choice B, which states that 1.00 Joule is equal to 0.239 calories, directly relates these two units of energy, fitting the concept of the mechanical equivalent of heat.

Question 7

Which of the following is the smallest unit of heat energy?

Accepted Answer

The Joule is the smallest unit of heat energy among the options given. It is the SI unit of energy, representing the amount of energy transferred to an object when a force of one newton acts on it over a distance of one meter.

Question 8

A substance with a greater specific heat ________ has a larger heat capacity.

Accepted Answer

A substance with a greater specific heat always has a larger heat capacity because specific heat capacity is a measure of the amount of heat energy required to change the temperature of a substance per unit mass. Therefore, a higher specific heat means more energy is needed to change the temperature, indicating a larger heat capacity.

Question 9

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater magnitude gain or loss of heat during the time the system takes to reach thermal equilibrium?

Accepted Answer

In a thermally isolated system, the heat lost by one object is equal to the heat gained by the other until thermal equilibrium is reached, regardless of their specific heat capacities.

Question 10

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium?

Accepted Answer

The answer of A thermally isolated system is made up...

Question 11

It is a well-known fact that water has a higher specific heat capacity than iron. Now, consider equal masses of water and iron that are initially in thermal equilibrium. The same amount of heat, 30. calories, is added to each. Which statement is true?

Accepted Answer

Since water has a higher specific heat capacity than iron, it requires more heat to change its temperature by the same amount. Therefore, when the same amount of heat is added to both, the iron, having a lower specific heat capacity, will warm up more than the water, leading to the iron being warmer.

Question 12

The heat required to change a substance from the solid to the liquid state is referred to as the

Accepted Answer

The heat required to change a substance from solid to liquid is called the heat of fusion.

Question 13

Steam will burn the skin more severely than boiling water because of water's relatively large

Accepted Answer

Steam causes more severe burns than boiling water because of its high latent heat, which is the energy released during the phase change from gas to liquid, resulting in more heat being transferred to the skin.

Question 14

A substance with a greater specific heat will ________ have a large latent heat.

Accepted Answer

Specific heat and latent heat are two different properties. A substance with a greater specific heat does not necessarily have a large latent heat, as these properties depend on the material's physical characteristics and phase change behavior.

Question 15

The specific heat of ice is about ________ the specific heat of liquid water.

Accepted Answer

The specific heat of ice is about half that of liquid water. This means it requires less energy to change the temperature of ice by one degree Celsius compared to the same mass of liquid water.

Question 16

When a vapor condenses into a liquid, its temperature

Accepted Answer

When a vapor condenses into a liquid, its temperature stays the same. Condensation is a phase change that occurs at a constant temperature, similar to boiling or melting.

Question 17

At higher altitudes water boils at ________ temperature as/than at sea level.

Accepted Answer

At higher altitudes, atmospheric pressure is lower than at sea level, causing water to boil at a lower temperature.

Question 18

Phase changes occur with an attendant

Accepted Answer

During a phase change, the temperature of a substance remains constant as the energy is used to change the phase rather than changing the temperature.

Question 19

At higher altitudes it takes ________ time to bring water to a boil on a stove.

Accepted Answer

At higher altitudes, atmospheric pressure is lower, which causes water to boil at a lower temperature. Therefore, it takes less time to bring water to a boil on a stove.

Question 20

Which of the following best explains why sweating is important to humans in maintaining suitable body temperature?

Accepted Answer

Sweating helps regulate body temperature through the process of evaporation. When sweat (which is mostly water) evaporates from the skin, it takes a significant amount of heat with it, cooling the body down. This is a key mechanism in thermoregulation, especially in hot conditions or during physical activity.

Quiz 11: Heat