Physics 101

Melting is a _______ ______ that requires energy ________ for the melting system. A) phase transition; input B) chemical change; input C) phase transition; release D) chemical change; release

A) phase transition; input

A quality perfume is a mixture of essential oils and has a scent that changes with time and skin temperature. Explain the gradual change of the perfume's scent with time in terms of evaporation. A. Different oils in the perfume evaporate at different rates. B. As more of the perfume evaporates, the scent changes. C. The perfume's scent changes as time passes. D. When the perfume is all evaporated, the scent will be gone.

A. Different oils in the perfume evaporate at different rates.

If you were laying steel track for a railroad, what influence would thermal expansion have on your work? A. I would need to account for the steel rail changing its size as the temperature rises and falls. B. It would not be a problem, as any changes in the size of the steel rail would be negligible. C. None, since thermal expansion does not occur with steel. D. It would not be a problem, since any temperature-related change in size of the rails would also apply to the wheels of the trains.

A. I would need to account for the steel rail changing its size as the temperature rises and falls.

If you add a little hot tea to ice water at 0 °C, the mixture will end up at 0 °C as long as some ice remains. Where does the tea's extra thermal energy go? A. It melts some of the ice. B. It is absorbed. C. It cools off. D. It warms up.

A. It melts some of the ice.

If you put a warm bottle of wine in a container of ice water, the wine will cool but the ice water won't become warmer. Where is the wine's thermal energy going? A. It melts some of the ice. B. It is absorbed. C. It cools off. D. It heats up.

A. It melts some of the ice.

An icy sidewalk gradually loses its ice even when the weather stays cold. Where does the ice go? A. It sublimes into the air. B. The sun melts it. C. Putting salt on the sidewalk will cause the ice to melt. D. It evaporates into the air.

A. It sublimes into the air.

Some air fresheners are solid materials that have strong odors. If you leave these air fresheners out, they slowly disappear. What happens to the solid material? A. It sublimes into the surrounding air. B. It evaporates into the surrounding air. C. It melts. D. It dissolves.

A. It sublimes into the surrounding air.

Your body is presently converting chemical potential energy from food into thermal energy at a rate of about 100 J/s, or 100 W. If heat were flowing out of you at a rate of about 200 W, what would happen to your body temperature? A. It would decrease. B. It would increase. C. It would remain constant. D. More information is needed to be able to answer.

A. It would decrease.

Use the concept of convection to explain why firewood burns better when it's raised above the bottom of a fireplace on a grate. A. Raising the wood allows convection to cause air to circulate around the wood, giving it more oxygen. B. Convection pulls in cooler air to the bottom. C. Convection causes warmer air to rise. D. Raising the wood allows convection to carry away the heat better.

A. Raising the wood allows convection to cause air to circulate around the wood, giving it more oxygen.

The molecules of antifreeze dissolve easily in water. Why does adding antifreeze to the water in a car radiator keep the water from freezing in the winter and boiling in the summer? A. The antifreeze lowers the freezing temperature and raises the boiling temperature of the water. B. It increases the pressure in the radiator, which keeps the water from freezing or boiling. C. The presence of the antifreeze chemically changes the water into a different compound, which cannot freeze. D. The antifreeze bonds with the radiator to keep the water from freezing.

A. The antifreeze lowers the freezing temperature and raises the boiling temperature of the water.

You have a roll of papered foil that is shiny on one side and black on the other. You wrap a cold potato salad in that foil. Which side should be facing outward to keep the salad cold longest? A. The foil side. B. The black side. C. It doesn't matter which side.

A. The foil side.

A difficult-to-open jar may open easily after being run under hot water for a moment. Explain. A. The heat from the water makes the lid expand and loosen. B. The water lubricates the lid. C. The heat from the water causes the air inside the jar to expand, exerting pressure on the lid. D. This doesn't really work; the effect is really an old wives' tale.

A. The heat from the water makes the lid expand and loosen.

A doctor can study a patient's circulation by imaging the infrared light emitted by the patient's skin. Tissue with poor blood flow is relatively cool. What changes in the infrared emissions would indicate such a cool spot? A. The infrared emissions from the cool spot would be less bright and shifted toward longer wavelengths. B. The infrared emissions from the cool spot would be less bright and shifted toward shorter wavelengths. C. The infrared emissions from the cool spot would be less bright. D. The infrared emissions from the cool spot would be shifted toward longer wavelengths.

A. The infrared emissions from the cool spot would be less bright and shifted toward longer wavelengths.

Explain how convection contributes to the shape of a candle flame. A. The rising warm air causes the flame to elongate upward. B. The warm air rises. C. Cooler air comes in at the bottom. D. The flame radiates heat upward.

A. The rising warm air causes the flame to elongate upward.

On a bitter cold day, the snow is light and powdery. This snow doesn't begin melting immediately when you bring it into a warm room. Why? A. The snow's temperature needs to rise to 0 °C before it can start melting. B. The snow needs to come up to room temperature before it can start melting. C. The snow needs some time before it can start melting. D. The warmth of the room takes a while to penetrate the snow.

A. The snow's temperature needs to rise to 0 °C before it can start melting.

Why are concrete sidewalks divided into individual squares rather than being left as continuous concrete strips? A. The space between the squares gives the concrete room to expand on a hot day. B. It is easier to pour concrete in squares than as a continuous strip. C. The space between the squares gives the concrete room to expand on a cold day. D. If a square is damaged it is cheaper to replace than if an continuous strip were damaged.

A. The space between the squares gives the concrete room to expand on a hot day.

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun sets near the seashore. A. The surface wind will blow from the land toward the water. B. The surface wind will blow alternately back and forth along the shore, parallel to the boundary between land and water. It will reverse directions every few minutes. C. The surface wind will blow steadily in one direction along the shore, parallel to the boundary between land and water. D. The surface wind will blow from the water toward the land.

A. The surface wind will blow from the land toward the water.

Astronomers can tell the surface temperature of a distant star without visiting it. How is this done? A. They use the color temperature of the star's light. B. They determine how much heat the star gives off. C. They use the red shift of the light. D. They determine the distance to the star.

A. They use the color temperature of the star's light.

How can water and ice coexist in a glass?

At 32°F (0°C), both phases are stable.

Wind is one of nature's ways of transferring energy through A. conduction. B. convection. C. transmission. D. radiation.

B. convection.

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because A. conduction carries heat downward toward the fire fighter and the aluminum tent conducts that heat harmlessly into the ground. B. radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation. C. convection carries heat downward toward the fire fighter and the aluminum tent blocks most of the heat carried by convection. D. both conduction and radiation carry heat downward toward the fire fighter and the aluminum tent blocks most of that heat.

B. radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation.

Housing and natural animal insulation works because A. the insulating materials are poorer heat conductors than air. B. the insulating materials trap air and prevent convection. C. the insulating materials prevent radiation. D. the insulating materials reflect radiation.

B. the insulating materials trap air and prevent convection.

Why do greenhouse gases warm the Earth?

By increasing altitude of Earth's radiating surface

Why does an ice cube feel cold? A) Heat from your hand enters the cube by convection. B) Cold from the cube enters your hand by convection. C) Heat from your hand enters the cube by conduction. D) Cold from the cube enters your hand by conduction.

C) Heat from your hand enters the cube by conduction.

Ice is A) amorphous B) very disordered C) crystalline D) just like liquid water only it move slower

C) crystalline

Why does the handle of a metal spoon submerged in boiling soup feel hot ? A. from the soup is transferred through the spoon by convection. B. The spoon has given up all its cold to the soup. C. Heat from the soup is transferred through the spoon by conduction. D. Heat from the soup is transferred through the spoon by radiation.

C. Heat from the soup is transferred through the spoon by conduction.

Freezing is a ____________ that requires energy ________ for the melting system. A. phase transition; input B. chemical change; input C. phase transition; release D. chemical change; release

C. phase transition; release

When cooking a potato in a conventional oven it is useful to stick a nail in it, which makes it cook faster. This is because A. the nail is a good radiator of heat. B. the nail promotes convection in the potato. C. the nail is a good conductor of heat. D. the nail gets much hotter than anything in the oven.

C. the nail is a good conductor of heat.

Which temperature scale has 373 as the boiling point of water? A) Fahrenheit B) Celsius C) Centigrade D) Kelvin

D) Kelvin

You are watching a science fiction movie where people on a space ship are traveling around the universe observing stars with different temperatures. Which of the following stars has the lowest surface temperature? A. A bluish star B. A yellowish star C. The sun D. A reddish star

D. A reddish star

Doctors use an infrared camera to look for inflammation, which appears as a hot patch on otherwise cooler skin. What differences would the camera observe at this hot patch? A.The hot patch would appear brighter than light from the surrounding skin. B.The light from the hot patch would be brighter and have a longer wavelength than light from the surrounding skin. C.The light from the hot patch would have a shorter wavelength than light from the surrounding skin. D.The light from the hot patch would be brighter and have a shorter wavelength than light from the surrounding skin.

D. The light from the hot patch would be brighter and have a shorter wavelength than light from the surrounding skin.

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun rises near the seashore. A. The surface wind will blow from the land toward the water. B. The surface wind will blow alternately back and forth along the shore, parallel to the boundary between land and water. It will reverse directions every few minutes. C. The surface wind will blow steadily in one direction along the shore, parallel to the boundary between land and water. D. The surface wind will blow from the water toward the land.

D. The surface wind will blow from the water toward the land.

You are a mechanic in a garage and are working on a carburetor that is made of metal, has a glass inspection window and plastic gears for the choke. If all three types of material are at the same temperature and each type of material is in contact with the other two, then A. heat will flow from the plastic to the glass, and from the glass to the metal. B. heat will flow from the metal to the glass, and from the glass to the plastic. C. heat will flow from the glass to both the plastic and the metal. D. no heat will flow between any parts.

D. no heat will flow between any parts.

Is salt the only chemical that helps melt ice?

No, any chemical that dissolves in water works.

Where do ice cubes go in a frostless freezer?

The ice sublimes directly into steam.

Can steam exist below 212°F (100°C)?

Yes, but its pressure is less than atmospheric.