Study Guide Chp 21, 22, 23

Study Guide chp 21, 22, 23

Name ______

A cup of tea with a temperature of 80°C is placed on a table in a 20°C room. What happens to the thermal energy and molecular motion of the tea when it is left on the table?

A. / The thermal energy increases and the molecules move faster.
B. / The thermal energy decreases and the molecules move faster.
C. / The thermal energy increases and the molecules move more slowly.
D. / The thermal energy decreases and the molecules move more slowly.

A small body of water contains 2,000 kg of water. The specific heat of water is4,180J/kg•°C.If the temperature of the water changes from 25°C to 20°C, approximately how much heat moves from the water to the surroundings?

A. / 8,400,000 J
B. / 42,000,000 J
C. / 168,000,000 J
D. / 210,000,000 J

Popcorn is made by heating corn kernels. Different methods may be used to heat the kernels.Which of the following methods uses radiation as the primary means of transferring energy to the corn kernels?

A. / heating corn kernels in a hot air popper
B. / heating corn kernels in a microwave oven
C. / heating corn kernels in a foil pan on a hot plate
D. / heating corn kernels in oil in a pot on an electric stove

A can of juice at 20°C is completely submerged in a closed, insulated container filled with water at 4°C, as shown in the diagram below.

1. Describe what happens to the temperature of the can of juice and the temperature of the water in the container within the first few minutes after the can is submerged. Explain your answer.

1. After four hours, will the can and the water have the same temperature or different temperatures? Explain your answer.

1. Estimate the numerical value(s) of the final temperatures of the can of juice and the water after four hours. Explain your answer.

A student touches a metal sink with her finger and notices that her finger feels cold. Which of the following statements explains this observation?

A. / Heat energy flows from the student’s finger to the metal sink.
B. / Heat energy flows from the metal sink to the student’s finger.
C. / The student’s finger was originally at the same temperature as the sink.
D. / The student’s finger was originally at a lower temperature than the sink.

The molecules in which of the following have the greatest average molecular kinetic energy?

A. / air in a person’s lungs
B. / ice cubes in a glass of iced tea
C. / raindrops collecting in a puddle
D. / water boiling in a pot on a stove

Two blocks of zinc with different masses are at room temperature. Each block then absorbs the same amount of heat over 10 minutes. When the temperature of each block is then measured, block 1 is at a higher temperature than block 2.Which of the following statements most likely describes the zinc blocks?

A. / The mass of block 1 is less than the mass of block 2.
B. / The mass of block 1 is greater than the mass of block 2.
C. / The specific heat of block 1 is less than the specific heat of block 2.
D. / The specific heat of block 1 is greater than the specific heat of block 2.

In which of the following examples is heat transferred primarily by radiation?

A. / A fan blows warm air around a room.
B. / A hot water bottle warms a person’s feet.
C. / Water vapor from a shower warms the room.
D. / A spoon held near the side of a flame gets warm.

A large container of cold water is moved from a refrigerator to a table. A hot piece of metal is placed into the water. Which of the following best describes the final temperature of the metal?

A. / higher than the final temperature of the water
B. / the same as the final temperature of the water
C. / lower than the initial temperature of the water
D. / the same as the initial temperature of the water

Which of the following is an example of heat transfer by conduction?

A. / sunlight heating a floor
B. / an electric stove heating an iron pan
C. / a wood stove heating nearby objects through electromagnetic waves
D. / an electric heater heating air, which rises and is replaced with cooler air

On a hot day, a student places a glass of cold lemonade on a table outdoors. After a few minutes, water droplets have formed on the outside of the glass.

1. Is energy absorbed or released by the cold lemonade? Explain your answer.

1. Compare average kinetic energy for the air molecules and lemonade molecules when the student first places the lemonade outdoors. Explain your answer.

1. Explain how and why the water droplets form on the outside of the glass.

A cup containing 25 mL of hot water and a similar cup containing 25 mL of cold water are placed on a table in a room at . Which of the following graphs shows the most likely change in temperature for each cup from 0 min to 40 min?

A. / / C /
B. / / D. /

A balloon is inflated with room-temperature air and then put in a sunny place. The balloon expands slightly due to a rise in temperature. Which of the following best describes the molecules of air inside the balloon when the balloon is left in the sunlight as compared to when it was first inflated?

A. / The molecules are moving faster.
B. / There are more molecules in the balloon.
C. / There are fewer interactions between the molecules.
D. / The molecules stop colliding with the walls of the balloon.

A car’s brakes absorb a large amount of energy and heat up as the car slows down and stops. Several materials with different thermal properties have been used for car brakes. In the table below, the specific heat capacities of three of these materials are shown.

Material / Specific Heat
Capacity
aluminum / 0.897
carbon-ceramic / 1.123
steel / 0.449

In an experiment, 500 g each of aluminum, carbon-ceramic, and steel are heated and their temperature changes are recorded. The amount of heat absorbed and the temperature change for the 500 g sample of steel are shown in the graph below.

• Draw a line on your graph to show the relationship expected for the 500 g sample of aluminum.
• Draw a line on your graph to show the relationship expected for the 500 g sample of carbon-ceramic.
• Identify each line on your graph, and explain why you drew each line where you did.

1. If brake materials get too hot they soften or melt, resulting in loss of braking power. Of the three materials in the table, which is best suited to resist large changes in temperature? Explain your answer.

The specific heat of wood is about 1,700. How much energy is required to heat a 12 kg piece of wood from 20°C to 30°C?Show all steps

A. / 1,400 J
B. / 17,000 J
C. / 204,000 J
D. / 612,000 J

Two full 2 L bottles of water are placed on a table. Bottle 1 was just removed from a refrigerator; bottle 2 is at room temperature. Which of the following statements describes the average molecular kinetic energy and the speed of the molecules in each bottle?

A. / Bottle 1 has the same average molecular kinetic energy as bottle 2, and the molecules have the same average speed in both bottles.
B. / Bottle 1 has a smaller average molecular kinetic energy than bottle 2, and the molecules have the same average speed in both bottles.
C. / Bottle 1 has a smaller average molecular kinetic energy than bottle 2, and the molecules have a slower average speed in bottle 1 than in bottle 2.
D. / Bottle 1 has a larger average molecular kinetic energy than bottle 2, and the molecules have a slower average speed in bottle 1 than in bottle 2.

Which of the following statements best explains why there is no change in temperature once thermal equilibrium between two objects in contact is reached?

A. / Heat can flow between two objects in contact.
B. / Heat does not flow between objects in contact at the same temperature.
C. / Heat does not flow spontaneously from a cooler object to a warmer object.
D. / Heat flows by conduction, convection, and radiation when the temperatures are the same.

The table below shows data from a heating experiment.

Metal / Heat
Added
(J) / Mass
of Metal
(g) / Change in
Temperature
(°C)
copper / 3000 / 100 / 77
iron / 3000 / 100 / 64
lead / 3000 / 100 / 231
silver / 3000 / 100 / 130

Which of the following conclusions is supported by the data in the table?

A. / A given mass of silver requires less heat to change its temperature 1°C than an equal mass of iron.
B. / A given mass of silver requires less heat to change its temperature 1°C than an equal mass of lead.
C. / A given mass of copper requires less heat to change its temperature 1°C than an equal mass of lead.
D. / A given mass of copper requires less heat to change its temperature 1°C than an equal mass of silver.

Which of the following statements best explains why drops of liquid form on the outside of a glass of ice water on a hot day?

A. / Water molecules in the air are attracted to the surface of the glass.
B. / Water molecules in the ice water lose energy as they transfer heat to the air.
C. / Water molecules in the air lose energy as they transfer heat to the cold glass.
D. / Water molecules in the ice water move through the glass pores to the outside of the glass.

student places an identical piece of wax on top of each block, as shown in the diagram below.

The student measures the time it takes for the piece of wax on each block to melt. Which of the following questions is being studied in this experiment?

A. / What is the melting point of the wax?
B. / What is the melting point of each metal?
C. / Which metal radiates heat the best?
D. / Which metal conducts heat the best?

The figure below represents water in a flask being heated by a hot plate.

Which of the following actions will slow down the rate of temperature increase of the water in the flask?

A. / covering the flask with a piece of foil
B. / adding more water at room temperature
C. / increasing the temperature of the hot plate
D. / reducing the amount of water being heated

In a room at 21°C, 60 mL of water is poured into each of three cups. The water in cup 1 is at 15°C, the water in cup 2 is at 25°C, and the water in cup 3 is at 45°C.

1. Describe what happens to the temperature of the water in each cup over a one-hour period.

1. Describe what happens to the energy present in each cup over the one-hour period and explain why.

1. Explain how equilibrium is reached in the cups.

A recycling plant manager needs to melt 1500 kg of scrap copper to sell to a wire manufacturer. The copper is at 15°C and
its melting point is 1083°C. The copper has a specific heat of 385 J/kg • K. How much heat is required to raise
the temperature of the copper to its melting point? Show all steps and formula

A. / 6.2 × 108J
B. / 6.3 × 108J
C. / 7.7 × 108J
D. / 7.9 × 108J

Measurements inside a sealed container show that the pressure exerted by a gas increases as the thermal energy of the gasincreases.

Which of the following best explains this pressure increase?

A. / The gas molecules stick to the walls of the container.
B. / The gas molecules radiate energy in the form of nuclear particles.
C. / The gas molecules begin to bond together into heavier molecules.
D. / The gas molecules move faster and strike the container walls more frequently.