Chapter 7 (Physics)

Describe how a boiling liquid can be used to cool something (IE, a refrigerator ) .

A low boiling liquid absorbs heat energy, dropping the temperature.

Water is most dense at

+4 degree C.

What happens to the boiling temperature of water as atmospheric pressure increases?

The boiling temperature goes up.

Why does evaporation cool a liquid?

The departing gas molecule takes some kinetic energy with it as it leaves the surface.

If you add heat energy to water molecules in the form of ice, where does the energy go?

The energy is used to break hydrogen bonds.

Why does liquid water expands slightly at low temperatures

The molecular vibrations start to slow and the molecules move farther apart due to directional hydrogen bonds.

What happens when you increase the temperature of a substance?

The molecules start to vibrate and move farther apart.

What happens when you increase the temperature of water ?

The molecules start to vibrate and move farther apart.

Why won't a paper cup filled with water burn if held to a flame?

The paper cannot become much hotter than the water it contains.

Unlike freshwater, ocean water contracts as it is cooled all the way down to its freezing point, which is about -18 degrees C. Why?

The presence of a solute disrupts the rate of ice microcrystal formation.

Why can you determine wind direction by wetting your finger and holding it up in the air?

The wind hitting your finger cools the water down, slowing down evaporation. So the cooler side of your finger is windward.

How many grams of 100° C steam I required to melt one gram of 0 degree C ice?

0.125 gram.

How many calories are required to heat 50 g of liquid water by 2 degrees C?

100 calories.

How many calories are needed to change 10 G of ice at 0 degrees C to steam at 100 degree C?

7200 cal

How many grams of 0 degree C ice can be melted by 1 gram of 100° C steam ?

8 grams

In what color metal pot will cold water warm to room temperature faster ?

A black pot.

If a material is a good conductor of heat ,how good of an insulator might it be?

A poor insulator.

When should you add cream to your hot coffee so that's coffee is the hottest when you are ready to drink it within a few minutes or right after it's served

Add the cream right when the coffee is served.

Will wrapping a bottle and wet cloth produce a cooler bottle then placing a bottle and a bucket of cold water?

As evaporation progresses, the average temperature of the liquid left behind can easily drop below the temperature of the cool water that wet it in the first place.

Why are metals good conductors of both heat and electricity ?

Because of the looseness of outer electrons in metal atoms.

Which glows with electromagnetic waves: the Sun or the Earth?

Both the Sun and the Earth

Why does warm air rise?

Faster-moving molecules tend to move to regions of less density and less pressure.

Why does condensation have the tendency to raise temperature of a liquid

Hydrogen bonding leads to an increase in the overall amount of kinetic energy in the water vapor.

Inside a balloon there are three gases in equal proportion: hydrogen, oxygen, and nitrogen. The molecules of which gas has the greatest average speed?

Hydrogen.

Ice floats in room temperature water, but does it float in boiling water? Why or why not?

If boiling water is less dense than ice, the ice cube should sink.

Does a liquid release or absorb energy as a transforms to a solid phase

It absorbs energy.

What effect does melting snow have on the surrounding air

It cools the surrounding air.

Why is food cooked quicker within a pressure cooker?

It has a higher temperature.

With an increase in air pressure over the surface of a cup of water, what happens to the tendency of the water to boil ?

It prevents boiling.

How long does it take to boil water on a Mountaintop compared to at sea level

It takes less time than at sea level.

What happens to the surrounding air as snow forms in a cloud ?

It warms.

What would happen to the nighttime environment if Air were a better conductor of heat?

It would be considerably colder.

: If You Were Somehow able to sit at the surface of an ice cube and were able to blow the movement of water molecules from the solid to the liquid phase, what would eventually happen to the Ice Cube?

It would increase in size.

Describe what happens when a given mass of liquid starts to expand?

Its density decreases.

What happens to the internal energy of an object as it radiates more energy than it absorbs?

Its internal energy decreases.

As the temperature of a piece of metal increases, what happens to the wavelength of its radiation?

Radiation wavelengths get shorter.

Primarily, how does Earth lose its heat?

Radiation.

What happens to the boiling temperature of water as salt is added?

Salt raises the boiling point of water

Which involves more energy: transforming 100 degrees C stream to 100° C liquid water, Or transforming 100 degree C liquid water to -273 degree C solid ice?

The 100 degree C steam to 100 degree C liquid water.

Why does the Sun have shorter wavelengths of radiant energy than Earth?

The Sun has a higher temperature than the Earth.

Your instructor hands you a closed flask of a room temperature water. When you hold it, the heat from your bare hand causes the water to boil. Quite impressive! How is this accomplished?

The air in the flask is very low in pressure, so that the heat from your hand (not the pressure from your hanwill produce boiling at this reduced pressure.

After a sunny day which will be warmer a Black or White Road surface?

The black surface.

Where is the boiling point of water the greatest: at the bottom of a pot of water or just below the surface ?

The boiling point of water is greatest where the water pressure is least, which is just below the surface.

Water coming out of volcanic sea vents at the bottom of the ocean can reach temperatures in excess of 300 degrees C without boiling. How is this possible ?

The extreme pressure exerted by the miles of ocean water above prevent the formation of any bubbles of water vapor.

It takes longer to cook food in boiling water at high elevation. But if you were to increase the heat supplied to the boiling water, then how would that impact the time to cook?

The food would cook at the same slow rate.

why does evaporation of a liquid also cool the gas above it ?

The gas molecules need to transfer their kinetic energy to the new slower gas molecule.

A sample of hydrogen gas and a sample of oxygen gas have the same temperature. How do the average speeds of molecules compare?

The hydrogen molecules will have the same kinetic energy, but greater average speed.

What happens to the heat causing a block of 0 degrees C ice to melt ?

The ice absorbs this heat but does not change its temperature.

Describe what happens to an ice cube and some water at 0 degree C if you increase the rate of water formation?

The ice cube melts.

Why doesn't the temperature of boiling water increase as heat is added?

The increased heating produces increased boiling, and therefore increased cooling.

Walking barefoot over red-hot wooden coals is possible for what reason?

The low thermal conductivity of the coals.

What would happen to the oceans if the atmosphere suddenly disappeared?

The missing air would be replaced by water vapor as the upper layers of the ocean began to boil.

What normally describes what happens when you decrease the temperature of a typical liquid ?

The molecular vibrations start to slow and the molecules move closer together, increasing the density.

What normally describes what happens when you decrease the temperature of water?

The molecular vibrations start to slow and the molecules move farther apart, decreasing the density.

A weighted wire passes through ice through a process called regelation, which depends upon what?

The open-structured nature of ice crystals.

Like water, hydrogen fluoride,HF, and ammonia,N, have relatively high boiling points. Explain.

The polar molecules of each of these materials have relatively strong attractions for themselves, which translates to relatively high boiling points.

For an ice/water mixture at 0 degrees Celsius, which is true?

The rate at which ice melts and freezes are both equal.

Why does a rug feel warmer than a stone floor at the same temperature ?

The rug is a better insulator than stone.

What happens to the temperature of boiling water as heat is added to it

The temperature does not change.

What happens to the temperature of a volume of air being compressed?

The temperature increases

what happened to the average speed of helium atoms when you double their absolute temperature? (assume a non ideal gas)

The temperature less than doubles.

What is the molecules of a gas never collided with each other. What would happen to the temperature of the gas?

The temperature would stay the same.

Why does a sweet potato only freeze at temperatures below 0 degrees C and not exactly at 0 degrees C?

The water in them contains dissolved salts and sugars.

Why does sweat cool you off ?

The water molecules leaving the skin as vapor absorb the heat from your skin.

You have a glass of ice cold water with ice in it and a glass of ice cold water with no ice in it. Which warms up faster on a warm day?

The water with no ice warms up faster.

After a clear night sky, which will be warmer: a Black or White Road surface

The white surface.

How do the radiation waves emitted by the Earth compare to the waves emitted by the Sun?

They're the same except for their frequencies and wavelengths.

Does Newton's law of cooling apply to Heating ?

To both of cooling and heating.

Suppose that water is used in a thermometer instead of Mercury. If the temperature is at 4 degrees C and then changes, why can't the thermometer indicate whether the temperature is rising or falling?

Water is most dense at 4 degree C. The water in a water-filled thermometer at 4 degree C would expand as the water was cooled or heated

If a friend dared you to walk on super hot cool in your bare feet, would you want your feet to be : Wet, dry, or cold?

Wet

Do objects that release radiation well also absorb radiation well ?

Yes

Condensation is

always a warming process.

Why does a lake Freeze from the top down?

as cold water cools towards freezing it gets less dense

Power pressure and the boiling point of a compound related

as the pressure decreases the boiling point decreases

How does a material absorb heat ?

conduction. Convection. Radiation. (All of these)

What must you add to 0 degrees C ice to transform it to 0 degrees C water?

energy.

What phase of matter holds convection as a significant mechanism for heat transfer?

fluids.

If an object absorbs radiation well, then it is also a

good emitter of radiation.

it is easier to cool off on a dry day vs. a humid day because the rate of evaporation is

greater on a dry day and more heat is lost.

What do you know about the boiling temperature of a pot of water at the top of a mountain?

it boils at a lower temperature than at sea level.

Is the density of near-freezing water, which contains microscopic ice crystals, greater or less than the density of liquid water containing no microscopic ice crystals?

less dense

How many calories are required to melt 50g of 0° C ice?

none of these (on conceptual academy) Answer: (4,000 cal)

If an object reflects radiation well, then it is also a

poor absorber of radiation.

Does gas release or absorb energy as it transforms to a liquid phase?

releases

The formation of hydrogen bonds between water molecules

releases heat energy.

What happens to the temperature of something while it's boiling?

temperature stays the same

Boiling is when the

vapor pressure of a liquid equals the atmospheric pressure.

In what color metal pot will hot water cool faster ?

A black pot.

Is your eye's pupil a net absorber or emitter?

A net absorber of radiant energy.

If an evaporating liquid cools, then does something else warm? If so what?

All around, evaporation is a cooling process. Nothing is warmed by the process of evaporation.

Evaporation is ...

Always a cooling process.

In super cold weather with only a candle to keep you warm, you would best be in: an igloo, a tent, a wooden house, or a car?

An igloo

What happens to the freezing temperature of a saltwater solution as it becomes more concentrated?

As salt water becomes more concentrated, the temperature at which it freezes become lower because fewer water molecules of the liquid phase in contact with the ice.

Why are polar oceans most fertile in the autumn?

As the oxygen rich surface waters cool in the autumn, they sink to the bottom displacing the layer of decomposing organic matter, forcing it to rise, adding nutrients to the surface of the polar oceans.

Describe what is happening at the surface of liquid water?

At the surface there is a constant exchange of liquid and gaseous water. Fast moving water molecules leave the surface and become gas molecules. Slow moving gas molecules are captured by the liquid water. The gas molecules exchange with the liquid molecules. (All of these)

How can you effectively cook a hard-boiled egg on a Mountaintop?

Boil the eggs for a longer time.

What is the boiling temperature of a single water molecule? Does this question make sense?

Boiling involves the separation of many molecules (plural). With only one molecule, the concept of boiling is meaningless.

Why do Ice Cube's get smaller when left in the freezer for a long time?

Both of these occur: The ice cubes melt during the brief warming cycles of auto-defrost and freezer access, thus leaving the ice cubes smaller and making them stick together in clumps. & The water molecules of the ice sublime from the solid to gaseous phase without ever entering a liquid phase.

How does a refrigerator work?

By removing internal energy from inside the refrigerator.

How is food in the refrigerator cooled?

By vaporization of the refrigerating fluid.

How is the cooling inside the refrigerator produced?

By vaporizing the refrigeration liquid.

Why is calcium chloride, more effective at melting ice and sodium chloride, NaCI?

Calcium chloride produces three ion particles while sodium chloride produces only two. Greater numbers of ions are more effective at decreasing the number of water molecules entering the solid phase.

Why is condensation a warming process? What does condensation warm?

Condensation transfers slower, lower kinetic energy vapor molecules to the liquid state, thus raising the overall temperature of both the gas and liquid molecules in the process.

How can ice within a cooler be made to cool the contents of the cooler faster?

Cover the ice with salt.

Why does adding heat to ice water disfavor the rate of ice formation?

Heat increases the vibration of the water molecules, which breaks the hydrogen bonds. When heat is added, the water molecules are moving too fast to form hydrogen bonds, which gives it the structure that we call ice. Adding heat favors the rate of melting, as more hydrogen bonds are broken than formed by the ice in the ice-water (all the above)

Does a solid release or absorb energy as it transforms to a liquid phase?

It absorbs energy.

A warmed volume of air expands. What happens to an expanding volume of air?

It cools

Consider a lake that is uniformly 10 degree C. What happens to the oxygen rich surface water as it cools down to 4 degreesC?

It grows more dense and sinks towards the bottom.

What would happen to temperature of an object being a poor absorber but a good emitter

Its temperature would become less than its surroundings.

Given the same temperature, which moves faster. Light gaseous molecules or heavy gaseous molecules?

Light gaseous molecules move faster.

How does geyser work?

Like a coffee percolator.

How many calories are required to boil 50 grams of water?

More calories than are required to bring 50 grams of ice at absolute zero to the boiling point.

Water will boil spontaneously in a vacuum. Could you cook an egg in this boiling water?

No, because food is cooked by the transfer of thermal energy from the water to the food, and water at room temperature does not have enough thermal energy to cook an egg.

What do you know about the internal energy of an object behaves as a net radiator ?

Not much because internal energy is not temperature.

If you keep a mixture of water and ice at 0 degrees Celsius what will happen?

Nothing, the ice and water will stay the same.

How can you protect vegetables from freezing in an unheated basement on a super cold winter night ?

Place large tubs of water in the basement.

How does a solute such as salt or sugar affect the melting and freezing of water ?

Solutes slow the rate of ice formation.

Your inventor friend proposes a design of cookware that will allow boiling to take place at a temperature less than a hundred degrees so that food will be cooked with less energy comment on this idea.

This idea would not be very profitable because it is the high temperature and the resulting thermal energy given to the food that is responsible for cooking_if the water boils at a low temperature insufficient energy is given to cook the food.

At the molecular level, when a piece of ice is slowly melting water molecules are being

Two of these are correct.

Why does ice form at the surface of a body of freshwater instead of at the bottom ?

Water near the freezing point of 0 degree C is less dense than warmer water, and the colder water will "float" on the warmer water. This allows ice to form at the surface.

What is the gas found within a bubble of boiling water?

Water vapor

Under what conditions will an object be a net radiator of energy?

When its temperature is higher than its surroundings.

Why does water not freeze at 0 degrees C when either ions or molecules other than 0 are present ?

When molecules or ions are dissolved in the water, these solute molecules both take up space and inhibit the formation of the solid phase, thus lowering the freezing point temperature below 0 degree C.

Why does blowing over hot soup cool the soup?

When you blow over the top of a bowl of hot soup, you remove the warm vapor which tends to condense and reduce net evaporation above the bowl. When you blow over the top of a bowl of hot soup, the moving air reduces pressure atop the soup and increases the rate of evaporation. When you blow over the top of a bowl of hot soup, you increase net evaporation. (All of these)

Does putting a lid over a pot of water on a stove shorten the time it takes for the water to come to a boil? After the water is boiling, does use of the lid shorten the cooking time of food ?

Yes, the trapped heat quickens boiling; the lid also increases pressure on the boiling water which raises its boiling temperature, cooking food in a shorter time.

It is commonly thought that a can beverage will cool faster in the coldest part of a refrigerator. Knowledge of Newton's Laws of cooling. Will a can of soda cool fastest in the coldest part of the refrigerator?

Yes. Newton's Law of Cooling supports this common knowledge.

To lower the temperature of a burning material most efficiently, how does the fire fire apply water?

braids as a fine mist