Physics - Chapter 15: Temperature, Heat, and Expansion

Hot sand cools off faster at night than do plants and vegetation. This indicates that the specific heat capacity for sand is ______

less than that of plants

Does a substance that heats up quickly have a high or a low specific heat capacity?

low specific heat capacity

temperature

measure of the average translational kinetic energy per molecule of a substance; measured in degrees Celsius or Farenheit or in kelvins. temperature = (average translational KE) / particle

thermometer

measures temperature; invented by Galileo in 1602.

Which warms up faster when heat is applied - iron or silver?

silver

______ is proportional to the average "translational" kinetic energy of random molecular motion (motion that carries the molecule from one place to another).

temperature

The temperature of absolute zero is stated as _______

−273°C

Both heat and work are "energy in motion"

energy being transferred from one substance to another. Both are measured in energy units, usually joules.

Heat is ________ from a body of higher temperature to one of lower temperature.

energy in transit Once transferred, the energy ceases to be heat

Most materials _____ when they are heated.

expand

Ice is slippery because

its crystalline structure is not easily maintained at the surface.

When an iron ring is heated, the hole becomes

larger.

The direction of spontaneous energy transfer is always from a _____ object to a neighboring ____ object.

warmer to cooler

All matter is composed of continuously moving molecules. Because of this random motion, the atoms and molecules in matter have kinetic energy. The average kinetic energy of the individual particles produces an effect we can sense --- _______.

warmth.

Liquid water is more dense than ice because

water molecules in a liquid are closer together than water molecules frozen in ice, where they have an open crystalline structure.

Ice is less dense than water because

water molecules in ice crystals take up more space than water molecules in liquid water. Ice has a crystalline structure, with open-structured crystals. Water molecules in this open structure occupy a greater volume than in the liquid phase

Coriolis effect

(physics) an effect whereby a body moving in a rotating frame of reference experiences the Coriolis force acting perpendicular to the direction of motion and to the axis of rotation The effect of Earth's rotation on the direction of winds and currents.

Which of these is the largest amount of energy? 100 calories 5 joules 10 calories 1 Calorie

1 Calorie

The amount of heat needed to raise the temperature of 1 gram of water by 1°C is _______.

1 calorie

If you add 1 calorie of heat to 1 gram of water, you'll raise its temperature by

1° C

Water is most dense at _______.

4 degrees Celsius

What was the precise temperature at the bottom of Lake Michigan, where the water is deep and the winters long, on New Year's Eve in 1901?

4°C because the temperature at the bottom of any body of water containing any 4°C water has a bottom temperature of 4°C, for the same reason that rocks are at the bottom. Rocks are more dense than water, and 4°C water is more dense than water at any other temperature. So both rocks and 4°C water sink to the bottom. Water is also a poor heat conductor, so if the body of water is deep and in a region of long winters and short summers, the water at the bottom likely remains a constant 4°C year-round.

If a fast marble hits a random scatter of slow marbles, does the fast marble usually speed up or slow down? Of the initially fast-moving marble and the initially slow ones, which lose(s) kinetic energy and which gain(s) kinetic energy? How do these questions relate to the direction of heat flow?

A fast-moving marble slows when it hits slower-moving marbles. It transfers some of its kinetic energy to the slower ones. Likewise with the flow of heat. Molecules with more kinetic energy that are in contact with molecules that have less kinetic energy transfer some of their excess energy to the less energetic ones. The direction of energy transfer is from hot to cold. For both the marbles and the molecules, however, the total energy before and after contact is the same.

Between 0°C and 4°C, the volume of liquid water decreases as the temperature increases.

Above 4°C, water behaves the way other substances do: Its volume increases as its temperature increases.

calorie

Amount of energy needed to raise temperature 1 gram of water 1 degree C 1 calorie = 4.19 joules

When we speak about heat, we refer to _______.

Energy in transit.

True or false? Temperature is a measure of the total kinetic energy in a substance.

False. Temperature is a measure of the average (not total!) translational kinetic energy of molecules in a substance. For example, there is twice as much total molecular kinetic energy in 2 L of boiling water as in 1 L—but the temperatures of the two volumes of water are the same because the average translational kinetic energy per molecule is the same in each.

Suppose you apply a flame to 1 L of water for a certain time and its temperature rises by 2°C. If you apply the same flame for the same time to 2 L of water, by how much will its temperature rise?

Its temperature will rise by only 1°C because there are twice as many molecules in 2 L of water, and each molecule receives only half as much energy on average.

As water is cooled at the surface, it sinks until the temperature of the entire lake is 4°C.

Only then can the surface water cool to 0°C without sinking. Once ice has formed, temperatures lower than 4°C can extend down into the lake.

Q=cmΔT

Quantity of heat transferred = specific heat capacity x mass x temperature change

Why do fish benefit from water being most dense at 4°C?

Since water is most dense at 4°C, colder water rises and freezes on the surface, which means that fish remain in relative warmth!

Because water has a high specific heat capacity and is transparent, it takes more energy to warm the water than to warm the land.

Solar energy incident on the land is concentrated at the surface, but because sunlight on water extends beneath the surface, it is "diluted."

Why is it advisable to allow telephone lines to sag when stringing them between poles in summer?

Telephone lines are longer in summer, when they are warmer, and shorter in winter, when they are cooler. They therefore sag more on hot summer days than in winter. If the telephone lines are not strung with enough sag in summer, they might contract too much and snap during the winter.

If water were most dense at 0°C, it would settle to the bottom of a pond or lake. Water at 0°C, however, is less dense and "floats" at the surface.

That's why ice forms at the surface.

An iron thumbtack and a big iron bolt are removed from a hot oven. Both are red-hot and have the same temperature. When dropped into identical containers of water of equal temperature, which one raises the water temperature more?

The big iron bolt has more internal energy to impart to the water and warms it more than the thumbtack. Although both objects have the same initial temperature (the same average kinetic energy per molecule), the more massive bolt has more molecules and therefore more total energy—internal energy. This example underscores the difference between temperature and internal energy.

When the temperature of a substance is increased, its molecules or atoms jiggle faster and move farther apart, on the average.

The result is an expansion of the substance.

farenheit scale

The temperature scale on which water freezes at 32 degrees and boils at 212 degrees

celcius scale

The temperature scale on which zero and 100 are the temperatures at which water freezes and boils

kelvin scale

The temperature scale on which zero is the temperature at which no more energy can be removed from matter

internal energy

The total energy stored in the atoms and molecules within a substance. Changes in internal energy are of principal concern in thermodynamics. The grand total of all the energies inside a substance.

very deep ponds and lakes are normally not ice covered even in the coldest of winters

This is because all the water must be cooled to 4°C before lower temperatures can be reached. For deep water, the winter is not long enough to reduce an entire pond to 4°C. Any 4°C water lies at the bottom. Because of water's high specific heat capacity and poor ability to conduct heat, the bottom of a deep body of water in a cold region remains at a constant 4°C year-round. Fish should be glad that this is so.

Different materials require different quantities of heat to raise the temperature of a given mass of the material by a specified number of degrees.

This is partly due to different materials absorbing energy in different ways. The energy may be spread around among several kinds of energy, including molecular rotation and potential energy, which raises the temperature less. Except for special cases such as helium gas, the energy is always shared among different kinds of motion, but in varying degrees.

Which of these has the highest specific heat capacity? Iron Silver Soil Water

Water

Which has a higher specific heat capacity: water or sand?

Water has a higher specific heat capacity. Water has greater thermal inertia and takes a longer time to warm in the hot sunlight and a longer time to cool on a cold night. Sand has a low specific heat capacity, as evidenced by how quickly the surface warms in the morning sunlight and how quickly it cools at night. (Walking or running barefoot across scorching sand in the daytime is a much different experience than walking on cool sand in the evening.)

Why is ice water less dense than slightly warmer water?

When ice melts, not all the open-structured crystals collapse. Some microscopic crystals remain in the ice-water mixture, making up a microscopic slush that slightly "bloats" the water, increasing its volume slightly (Figure 15.19) As the temperature of water at 0°C is increased, more of the remaining ice crystals collapse. The melting of these crystals further decreases the volume of the water. The water undergoes two processes at the same time—expansion and contraction. Volume tends to increase due to greater molecular motion with increased temperature, while volume at and near 0°C decreases as ice crystals collapse upon melting. The collapsing effect dominates until the temperature reaches 4°C. After that, expansion overrides contraction because most of the microscopic ice crystals have melted by then.

If a certain material heats up quickly and cools down quickly, the material has _______.

a low specific heat

When the temperature of a strip of iron is increased, the length of the strip _______.

also increases

How does a thermostat work?

because of the thermal expansion of a bimetallic strip The back-and-forth bending of the bimetallic coil opens and closes an electric circuit. When the room becomes too cold, the coil bends toward the brass side, which activates an electrical switch that turns on the heat. When the room becomes too warm, the coil bends toward the iron side, which activates an electrical switch that turns off the heating unit. Refrigerators are equipped with thermostats to prevent them from becoming either too warm or too cold.

Most materials ____ when they are cooled.

contract

matter does not contain ___; instead it contains molecular kinetic energy and possibly potential energy.

heat

What's inside the open spaces of the water crystals shown in Figures 15.18 and 15.19? Is it air, water vapor, or nothing?

here's nothing at all in the open spaces. It's empty space—a void. If there were air or vapor in the open spaces, the illustration should show molecules there—oxygen and nitrogen for air and H2O for water vapor.

The moderate temperatures of islands throughout the world has much to do with water's

high specific heat.

Cold is the absence of ________

internal energy

thermal energy =

internal energy

A substance does not contain heat, it contains ___.

internal energy (thermal energy).

Which of the following normally warms up fastest when heat is applied?

iron

heat

the energy that "flows" from one object to another by virtue of a difference in temperature; measured in calories or joules.

absolute zero

the lowest possible temperature that any substance can have; the temperature at which the atoms of a substance have their minimum kinetic energy. The temperature of absolute zero is -273.15 C, which is -459.7 F, and 0 K.

specific heat capacity

the quantity of heat required to raise the temperature of a unit mass of a substance by 1 degree Celsius (or equivalently, by 1 kelvin); often simply called specific heat