Physics Chapter 21
Describe two ways a substance can change when it absorbs heat.
a) The molecules of the substance may jostle faster and the temperature of the substance will increase. b) The substance can change phase, and its temperature will not increase.
T/F: Heal always flows from a substance with more total molecular kinetic energy to a substance with less.
false
Identify where the Fahrenheit scale is primarily used.
used commonly in the United States
The high specific heat of ocean water near the west coast of North America causes the winters there to be ___ and the summers to be ___ than the east coast.
warmer; cooler
In order to quantify heat, we must specify the ___ and ___ of substance affected.
mass and kind
Why do most forms of matter expand when they are heated?
As the temperature of a substance is increased, its molecules jiggle faster and normally tend to move farther apart.
Why does ice float on water?
At 0 degrees Celsius, ice is less dense than water, and so ice floats on water.
T/F: Heat never flows on its own from a cooler substance into a hotter substance.
true
absolute zero on the Celsius scale
-273
what mass of copper will give up 240 calories when its temperature drops from 90.0 degrees Celsius to 30 degrees Celsius? (The specific heat capacity of copper is 0.092 cal/g degrees Celsius)
43 grams
Explain how a common liquid thermometer works.
A common thermometer indicates that expansion and contraction of a liquid in a glass tube using a scale.
Explain this statement: we can think of specific heat capacity as thermal inertia.
Inertia signifies the resistance of an object to a change in its state of motion. Specific heat capacity signifies the resistance of a substance to a change in its temperature.
___ is the grand total of all energies inside a substance.
Internal energy
Why does water have a higher specific heat capacity than iron?
Iron atoms primarily shake back and forth when they absorb energy, but water molecules soak up a lot of energy in rotations, internal vibrations, and bond stretching.
Why is it important for a thermometer to be small in comparison to the substance it is measuring?
It should not appreciably alter the temperature of the substance being measured.
How does matter change when heated or cooled?
Most forms of matter - solids, liquids, and gases - expand when they are heated and contract when they are cooled.
What is the title of section 21.6?
Specific Heat Capacity
Explain why Europe is much warmer than northeastern Canada, even though they are at similar latitudes.
The Gulf Stream brings warm water from the Caribbean. The water holds its internal energy long enough to reach the coast of Europe. Here the water warms the air, and the winds warm Europe.
How can you determine the amount of heat transferred to a substance?
The amount of heat transferred can be determined by measuring the temperature change of a known mass of a substance that absorbs the heat.
Why do different substances have different capacities to store heat?
The capacity of a substance to store heat depends on its chemical composition.
What is the title of section 21.7?
The high specific heat capacity of water
What is the relationship between the temperature of a substance and the speed of its molecules?
The higher the temperature of a substance, the faster is the motion of its molecules.
Define specific heat capacity?
The quantity of heat required to raise the temperature of a unit mass of the material by 1 degree.
Define Fahrenheit scale.
The temperature scale most widely used in the United States. The number 32 designates the temperature at which water freezes, and the number 212 is assigned to the temperature at which water boils (at 1 atm). The Fahrenheit scale will become obsolete if and when the United States goes metric.
Define thermostat.
a practical application of the bimetallic strip that is used to control temperature.
If concrete sidewalks and highway paving were laid down in one continuous piece, cracks would appear as the materials ___ on hot summer days and ___ on cold winter days.
expanded; contracted
Roadways on bridges often have tongue and grove type gaps called ___ to allow for thermal expansion.
expansion joints
T/F: A cup of hot water contains more heat than a cup of cold water.
false
Define calorie.
the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius
Define heat.
the energy that transfers from one object to another because of a temperature difference between them
Define absolute zero.
the lowest possible temperature at which a substance has no kinetic energy to give up
What is specific heat capacity?
the quantity of heat required to raise the temperature of a unit mass of the material by 1 degree
The capacity of a substance to store heat depends on its ___.
chemical composition
Define kilocalorie.
1000 calories (the heat required to raise the temperature of 1 kilogram of water by 1 degree Celsius).
After objects in thermal contact with each other reach the same temperature, the objects are in ___.
thermal equilibrium
Describe the spontaneous energy transfer that occurs when you touch a cube of ice.
Because your hand is warmer, energy moves from your hand into the colder ice.
Concept Check - What cause heat to flow?
Heat flows when two substances of different temperatures are in thermal contact.
Water boils on the Celsius scale
100
Define calorie.
The heat required to raise the temperature of 1 K of water by 1 degree Celsius.
What are two ways the internal energy of a substance can change?
by taking in or giving off heat
Divisions on the Celsius and Fahrenheit scales are called ___, but the divisions on the Kelvin scale are called ___.
degrees, Kelvins
T/F: For solids and liquids, temperature is unrelationed to the average kinetic energy of molecular translational motion.
false
A Calorie, used to describe the energy of ___, is equivalent to one ___.
food, kilocalorie
When a thermometer is in contact with a substance, heat flows between them until ____
they have the same temperature.
T/F: Water takes longer to heat to a certain temperature than most substances, and it take longer to cool.
true
Identify where the Kelvin scale is primarily used.
used in scientific reseach
Describe one way that each of the following handles the different rates of thermal expansion in materials. Dentist:
uses filling material that has the same rate of expansion as teeth
Describe one way that each of the following handles the different rates of thermal expansion in materials. civil engineer:
uses steel having the same expansion rate as concrete for reinforcing concrete
Define thermal contact.
when objects or substance are in contact such that heat flows from one to the other.
A 35 gram piece of silver is dropped into a container of water. As it cools, the silver's temperature change? (The specific heat capacity of silver is 0.056 cal/g degrees Celsius)
-92 degrees Celsius
Water freezes on the Celsius scale
0
Specific Heat Capacities: Material (J/g degrees C) (cal/g degrees C) Aluminum 0.900 0.215 Copper 0.386 0.092 Lead 0.128 0.031 ___ calorie(s) of heat are needed to raise the temperature of 1 gram of aluminum by 1 Celsius degree.
0.215
Specific Heat Capacities: Material (J/g degrees C) (cal/g degrees C) Aluminum 0.900 0.215 Copper 0.386 0.092 Lead 0.128 0.031 ___ joule(s) of heat are needed to raise the temperature of 1 gram of lead by 2 Celsius degrees.
0.256
Specific Heat Capacities: Material (J/g degrees C) (cal/g degrees C) Aluminum 0.900 0.215 Copper 0.386 0.092 Lead 0.128 0.031 ___ joule(s) of heat are needed to raise the temperature of 2 grams of copper by 1 Celsius degree.
0.772
Water boils on the Fahrenheit scale
212
A 50 gram strip of aluminum is heated to 100 degrees Celsius. It is then dropped into a container of water where it gives off 753 calories of heat. What is the final temperature of the aluminum? (The specific heat capacity of aluminum is 0.215 cal/g degrees Celsius.)
30 degrees Celsius
Water freezes on the Fahrenheit scale
32
Water is the most dense at a temperature of ___.
4 degrees Celsius
One calorie is equivalent to ___ joules, the SI unit for all forms of energy.
4.186
Define thermal equilibrium.
After object in thermal contact with each other reach the same temperature, the objects are said to be in thermal equilibrium.
There is a figure of a pond. On the surface of the pond, it is -10 degrees Celsius. There is a layer of ice. Just below the ice is it 0 degrees Celsius. There is a fish and at the bottom of the pond it is 4 degrees Celsius. What must be true in order for ice to begin forming at the surface of the pond?
All the water below it must be at 4 degrees Celsius.
There is a figure of a pond. On the surface of the pond, it is -10 degrees Celsius. There is a layer of ice. Just below the ice is it 0 degrees Celsius. There is a fish and at the bottom of the pond it is 4 degrees Celsius. What must be true in order for the water at 4 degrees Celsius to remain at the surface?
All the water below it must have at least an equal density, for example, all the water below must be at 4 degrees Celsius.
Describe how the thermal expansion and contraction of water is different from most other materials.
Almost all liquids expand when they are heated. Between the temperatures of 0 degrees Celsius and 4 degrees Celsius, water's volume decreases.
Concept check: Why does ice float on water?
Ice floats on water because at 0 degrees Celsius, isce is less dense than water so ice floats on water.
How can you determine the amount of heat transferred from one substance to another?
Measure the temperature change of a know mass of the substance that absorbs the heat.
Complete the table by writing increase or decrease to describe how the volume and density of water changes during teach temperature change. Temperature Change Change in Volume Change in Density 0 to 4 degrees Celsius 4 to 10 degrees Celsius
Temperature Change Change in Volume Change in Density 0 to 4 degrees Celsius decrease increase 4 to 10 degrees Celsius increase decrease
Explain how the bimetallic strip in the figure above (see book with figure of ice on strip of brass/iron and candle under strip of brass/iron) is affected in each case: Heated by a flame:
The brass becomes longer than the iron, causing the strip to bend toward the iron.
Explain how the bimetallic strip in the figure above (see book with figure of ice on strip of brass/iron and candle under strip of brass/iron) is affected in each case: Cooled by ice:
The brass becomes shorter than the iron, causing the strip to bend toward the brass.
Explain the meanings of the terms thermal energy and internal energy.
The energy that results from heat flow is thermal energy. Scientists prefer to call the energy that results from heat flow internal energy.
What is the relationship between the temperature of a substance and the rate of motion on its molecules?
The faster the motion of the molecules, the higher the temperature of a substance.
Define internal energy.
The grand total of all energies inside a substance.
Define Celsius scale.
The most widely used temperature scale where the number 0 is assigned to the temperature at which water freezes, and the number 100 to the temperature at which water boils (at standard atmospheric pressure). The gap between freezing and boiling is divided into 100 equal parts, called degrees.
What is the effect of water's high specific heat capacity on climate?
The property of water to resist changes in temperature improves the climate in many places.
Define Kelvin scale.
The temperature scale used in scientific research is the SI scale - the Kelvin scale. Its degrees are the same size as the Celsius degree and are called Kelvins. On the Kelvin scale, the number 0 is assigned to the lowest possible temperature - absolute zero. At absolute zero, a substance has no kinetic energy to give up.
Suppose you have a 2 liter pot of boiling water, and you pour out 1 liter of the water. Explain whether the average kinetic energy and the temperature of the water in the pot has changed.
The total kinetic energy is half the original value, but the average kinetic energy, and thus the temperature, is unchanged.
When two substance of different temperature are in thermal contact, heat flows from the ___ substance into the ___ substance.
higher temperature, lower temperature
There is a figure of a pond. On the surface of the pond, it is -10 degrees Celsius. There is a layer of ice. Just below the ice is it 0 degrees Celsius. There is a fish and at the bottom of the pond it is 4 degrees Celsius. What determines whether the water will float at the surface?
The water will float only if it is as dense or less dense than the water below.
What is the title of this chapter?
Thermal Energy
Define bimetallic strip.
Two strips of different materials, such as one of brass and one of iron, welded or riveted together into one strip. Because the two substances expand at different rates, when heated or cooled, the strip bends.
Explain why water has such an unusual thermal expansion and contraction behavior.
Water molecules in their crystal form have an unusual open structure. Water molecules in this open structure occupy a greater volume than they do in the liquid state.
What happens to the internal energy of a substance that takes in or gives off heat?
When a substance takes in or gives off heat, its internal energy changes.
How does a thermometer measure temperature?
When a thermometer is in contact with a substance, heat flows between them until they have the same temperature.
What is the big idea of Chapter 21: Temperature, Heat and Expansion?
When matter gets warmer, the atoms or molecule in the matter move faster.
Describe how a thermostat uses a bimetallic strip.
When the room becomes too cold, the bimetallic coil bends toward the brass side and closes an electric switch that turns on the heat. When the room becomes too warm, the coil bends toward the iron side and opens the electric switch, turning off the heat.
What causes heat to flow?
When two substance of different temperatures are in thermal contact, heat flows from the higher-temperature substance into the lower-temperature substance.
Name four types of energy within substances.
a) translational kinetic energy b) rotational kinetic energy c) kinetic energy due to internal movements of atoms within molecules d) potential energy due to the forces between molecules
Describe one way that each of the following handles the different rates of thermal expansion in materials. Automobile engines:
aluminum pistons are enough smaller in diameter than the steel cylinder to allow for the greater expansion rate of aluminum
There is a figure of a pond. On the surface of the pond, it is -10 degrees Celsius. There is a layer of ice. Just below the ice is it 0 degrees Celsius. There is a fish and at the bottom of the pond it is 4 degrees Celsius. Where does most of the cooling in the pond take place?
at its surface
Which below is the number of kilocalories that equals 50,000 calories. a) 5 b) 50 c) 500 d) 5000
b) 50
Suppose you place a pot with 1 cup of water and an identical pot with 2 cups of water on a hot stove for the same amount of time. Which below correctly describe what happens? a) More heat is added to the pot with 2 cups of water. b) The same amount of heat is added to both pots. c) The temperature of the pot with 1 cup of water increase more. d) The temperature increase of both pots is the same.
b) The same amount of heat is added to both pots. c) The temperature of the pot with 1 cup of water increase more.
Identify where the Celsius scale is primarily used.
most widely used by people worldwide
Define translational motion.
motion along a straight or curved path
There is a figure of a pond. On the surface of the pond, it is -10 degrees Celsius. There is a layer of ice. Just below the ice is it 0 degrees Celsius. There is a fish and at the bottom of the pond it is 4 degrees Celsius. If only some of the water in a deep pond is 4 degrees Celsius, where will it be?
on the bottom of the pond
For an ideal gas, temperature is ___ to the average kinetic energy of molecular translation motion.
proportional
Define specific heat capacity.
the quantity of heat required to raise the temperature of a unit mass of the material by 1 degree.
Define temperature.
the quantity that tells how hot or cold something is compared with a standard
