Chapter 3: States of Matter

How does the energy of a system change during a phase change?

Energy is either released or absorbed during a phase change.

What is the difference between evaporation and boiling?

Evaporation takes place at the surface of a liquid and occurs at temperatures below the boiling point.

How does the frequency of collisions affect the pressure of a gas?

The more frequent the collisions, the greater the pressure of the gas is

What three assumptions about particles in a gas are made by the kinetic theory?

The particles are in constant, random motion. The motion of one particle is unaffected by the motion of other particles unless the particles collide. Under ordinary conditions, forces of attraction between particles can be ignored.

Explain why a solid has a definite shape and volume.

The particles in a solid vibrate around fixed locations.

What does the kinetic theory say about the motion of atoms?

All particles of matter are in constant motion

Explain why the temperature of water does not rise during boiling.

Energy absorbed by the system during boiling is used to overcome attractions among water molecules.

How is Boyle's law expressed mathematically?

P1V1 = P2V2

Compare the melting and freezing of water in terms of (a) the temperature at which these processes take place and (b) the energy involved in these processes

(a) Water melts and freezes at the same temperature. (b) Melting is an endothermic process. Freezing is an exothermic process.

A gas sample occupies 4.2 L at a pressure of 101 kPa. What volume will it occupy if the pressure is increased to 235 kPa?

1.8L

How much energy does one gram of ice absorb as it melts?

334 joules

An automobile tire has a pressure of 325 kPa when the temperature is 10 degrees C. If the temperature of the tire rises to 50 degrees C and its volume is constant, what is the new pressure?

371 kPa

If you take a helium balloon from inside a warm house to outside on a snowy day, what will happen to the balloon? Could you classify this change as a phase change? Explain your answer.

A balloon that is flexible will shrink. This observed change is not a phase change because helium is a gas before and after the change.

In Earth's atmosphere, pressure and temperature both decrease as altitude increases. Weather balloons expand as they rise. Which has more effect on the weather balloon, the decrease in pressure or the decrease in temperature? Explain your answer.

A decrease in pressure causes an increase in volume. A decrease in temperature causes a decrease in volume. Because the volume of a balloon increases, the decrease in pressure must affect the balloon more than the decrease in temperature.

Explain why sublimation and deposition are classified as physical changes.

A substance's identity does not change during sublimation or deposition.

Some liquid products are solid in aerosol cans. Gas is stored in a can under pressure and is used to propel the liquid out of the can. Explain why an aerosol can should never be thrown into a fireplace or incinerator.

At a high temperature, the pressure in the gas might increase to the point where the can would explode.

A student examines a thermometer placed in a can containing a substance that is being heated. the temperature remains the same for several minutes, and then it starts to rise. Without looking in the can, how does the student know what is occurring in the can?

Because energy is being added but no increase in temperature occurs, a phase change is occurring in the can.

What happens to the pressure in a tire if air is slowly leaking out of the tire? Explain your answer.

Because the number of particles of air is reduced from the leak, the pressure will slowly decrease.

What do Boyle's law and Charles's law have in common? How are they different?

Both laws describe a relationship between two variables that affect a gas when other variables are constant. Charles's law shows how the volume of a gas is directly proportional to its temperature in kelvins. Boyle's law shows how the volume of a gas is inversely proportional to its pressure.

Compare and contrast liquid water and ice in terms of how definite their shapes and volumes are.

Both liquid water and ice have a definite volume. Ice has a definite shape, but liquid water does not.

How is the gas pressure produced in a closed container of gas?

Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of gas.

How does an endothermic phase change differ from an exothermic phase change?

During an endothermic phase change, energy is absorbed by the system. During an exothermic phase change, energy is released by the system.

Using the kinetic theory, explain what causes gas pressure.

Gas pressure is caused by collisions of atoms with their containers.

How can atoms behave at temperatures near -273 degrees C?

Groups of atoms can behave as though they were a single particle.

Unpopped popcorn kernels contain a small amount of water. Use what you know about vaporization and how gases behave to explain why popcorn pops when it is heated

Heating causes the water to vaporize. With continued heating, the pressure of the vapor increases because the volume of the confined vapor is constant. Eventually, the increased pressure causes the kernel to burst open.

What happens to the pressure of a gas if its volume is reduced?

If the volume is reduced, the pressure of a gas increases if temperature and number of particles are constant.

How does increasing the number of particles of a contained gas affect its pressure?

Increasing the number of particles will increase the pressure if temperature and volume are constant.

How are shape and volume used to classify solids, liquids, and gases?

Materials can be classified a s solids, liquids, or gases based on whether their shapes and volumes are definite or variable.

Name six common phase changes.

Melting, freezing, vaporization, condensation, sublimation, and deposition.

The pressure of a gas is directly proportional to its temperature in kelvins. Using P1, P2, T1, and T2, write a mathematical equation that expresses this relationship.

P1/P2=T1/T2 or P1/T1=P2/T2

Describe the motion of particles in a gas.

Particles in a gas are in constant, random motion.

Use kinetic theory and attractive forces to explain why a liquid has a definite volume and a shape that can vary.

Particles in a liquid can flow to new locations, but forces of attraction keep the particles close together.

How does increasing the temperature affect the pressure of a contained gas?

Raising the temperature will increase the pressure if volume and number of particles are constant.

At room temperature, table salt is a solid and acetone is a liquid. Acetone is the main ingredient in nail polish remover. What conclusion can you draw about the melting points of these materials?

Table salt must have a melting point above room temperature, and acetone must have a melting point below room temperature.

What three factors affect gas pressure?

Temperature, volume, and number of particles

What three factors affect the pressure of a gas in a closed container?

Temperature, volume, and the number of particles

What happens to the arrangement of water molecules as water melts and freezes?

The arrangement of molecules becomes less orderly as water melts and more orderly as water freezes.

How does the arrangement of atoms in most solids differ from the arrangement of atoms in a liquid?

The atoms in most solids have a more orderly arrangement than the atoms in liquids, which are not restricted to fixed locations.

How is a gas able to fill a container of any size or shape?

The constant motion of gas particles allows a gas to fill a container of any shape or size.

How does the surface area of a liquid affect the rate of evaporation?

The greater the surface area, the faster the water evaporates.

What happens to the speed of the particles inside an air-filled balloon if the temperature of the balloon increases?

The particles in the air move faster, on average, when the temperature increases because they have more kinetic energy.

A hazardous chemical is leaking from a tank truck. Rescue workers need to evacuate people who live near the accident. Why are more people likely to be affected if the chemical is a gas, rather than a liquid?

The particles of a gas have greater freedom of movement and will reach a wider area more quickly.

What happens to the pressure inside a weather balloon as it rises?

The pressure increases

In a car engine, air and gasoline vapors are mixed in a cylinder. A piston is pushed into the cylinder before a spark ignites the mixture of gases. When the piston is pushed into the cylinder, what happens to the pressure of the gases in the cylinder?

The pressure increases.

What happens to the temperature of a substance during a phase change?

The temperature of a substance does not change during a phase change.

Compare the vapor pressure of water at 10 degrees C with its vapor pressure at 50 degrees C.

The vapor pressure of water is greater at 50 degrees C than it is at 10 degrees C.

If a piston moves downward in a cylinder, what happens to the volume and pressure of the gas in the cylinder? The temperature remains constant.

The volume decreases and the pressure increases.

How are the pressure and volume of a gas related?

The volume of a gas is inversely proportional to its pressure.

If there is a gas leak in the basement of a building, you will soon notice an odor, throughout the house. However, if there is a water leak in the basement, you will need to go to the basement to detect the leak. Use the Kinetic theory to explain the differences.

There is almost no attraction between particles in a gas. they will quickly spread throughout the building. Because particle sin a liquid strongly attract one another, they remain close together and don't spread throughout the building (unless the water quantity is large and there is no drain)

Explain why a farmer would need to keep spraying the plants with water while the temperature remains below freezing.

Until the temperature rises above freezing, the farmer must continue to provide energy to keep the plants from freezing.

Explain why water has a different boiling point at an elevation of 3000 meters than it does at sea level.

Water boils when its vapor pressure becomes equal to atmospheric pressure. At 3000 m, the atmospheric pressure is lower than it is at sea level. Thus, vapor pressure equals atmospheric pressure at a lower temperature, and water boils at a lower temperature.

How can the mass of a pile of snow decrease on a sunny day when the air temperature does not rise above 0 degrees C?

When snow absorbs energy from sunlight, it either melts or sublimes.

Using the kinetic theory, explain why the pressure of a gas increases when its temperature increases.

When the temperature of a gas increases, the particles have greater kinetic energy, on average, and move faster. Thus, atoms hit the walls of the container more often and with greater force, causing the pressure to increase.

Explain how the behavior of popcorn in a popcorn popper can be used as an analogy for the motion of gas particles.

While popping occurs, the motion of the individual popcorn kernels is random and fairly continuous.

What is endothermic?

a description of a change in which a system absorbs energy from its surroundings

What is exothermic?

a description of a change in which a system releases energy to its surroundings.

What is a phase change?

a reversible physical change that occurs when a substance changes from one state of matter to another.

What is absolute zero?

a temperature of 0 kelvins

Which of these statements about an enclosed gas is true? (Assume all quantities are constant except the two variables described in each statement.) a) Raising the temperature of a gas will increase its pressure. b) Increasing the volume of a gas will increase its pressure. c) Reducing the number of particles of a gas will increase its pressure. d) The volume of a gas is inversely proportional to its temperature in kelvins. e) The volume of a gas is directly proportional to its pressure.

a) Raising the temperature of a gas will increase its pressure.

The SI unit of pressure is the a) pascal. b) newton. c) square meter. d) psi.

a) pascal.

Which of these phase changes does NOT involve changing a liquid into a gas? a) sublimation b) vaporization c) evaporation d) boiling

a) sublimation

Which of the following changes is exothermic? a) evaporation b) freezing c) boiling d) sublimation

b) freezing

If the speed of an object increases, its kinetic energy a) decreases. b) increases. c) stays the same. d) is unpredictable.

b) increases.

Which state of matter has a definite volume but a variable shape? a) solid b) liquid c) gas d) vapor

b) liquid

Which statement best explains what must take place for water to boil? a) The water releases energy to its surroundings. b) Bubbles rise to the surface of the water. c) The vapor pressure of the water becomes equal to atmospheric pressure. d) Molecules at the surface of the water overcome the attractions of neighboring molecules. e) The temperature of the water increases.

c) The vapor pressure of the water becomes equal to atmospheric pressure.

Which statement is true about the atoms in helium gas? a) They travel in circular paths. b) They have strong attractions to one another. c) They are not closely packed. d) They are arranged in an orderly pattern.

c) They are not closely packed.

The phase change that is the reverse of vaporization is a) freezing b) melting c) condensation d) evaporation

c) condensation

A material can be classified as a liquid if a) it has a definite shape and a definite volume. b) it has a definite shape and a variable volume. c) it has a variable shape and a definite volume. d) it has a variable shape and a variable volume. e) its particles vibrate around fixed locations.

c) it has a variable shape and a definite volume.

In which state(s) of matter can materials take the shape of their containers? a) solid and liquid b) solid and gas c) liquid and gas d) liquid only

c) liquid and gas

Boyle's law relates pressure and a) temperature b) number of particles c) volume d) mass

c) volume

During an endothermic phase change, a) the temperature of a substance rises. b) the temperature of a substance decreases. c) energy is transferred from a substance to its surroundings. d) a substance absorbs energy form its surroundings. e) there is no transfer of energy.

d) a substance absorbs energy form its surroundings.

Increasing which variable would decrease the pressure of a contained gas? a) temperature b) number of particles c) boiling point d) volume

d) volume

Condensation is the phase change in which a substance changes from a) a solid to a gas. b) a solid to a liquid. c) a liquid to a solid. d) a liquid to a gas. e) a gas to a liquid.

e) a gas to a liquid.

What is Charles's Law?

the direct proportion of the volume of a gas to its temperature (in kelvins) if the pressure and the number of particle sof the gas are constant

What is heat of vaporization?

the energy a substance must absorb in order to change from a liquid to a gas

What is heat of fusion?

the energy a substance must absorb in order to change from a solid to a liquid

What is Kinetic energy?

the energy an object has due to its motion

What is Boyle's Law?

the inverse variation of the volume of a gas with its pressure if the temperature and the number of particles are constant

What is deposition?

the phase change in which a gas or vapor changes directly into a solid without first changing into a liquid

What is vaporization?

the phase change in which a substance changes form a liquid into a gas

What is condensation?

the phase change in which a substance changes from a gas or vapor to a liquid

What is sublimation?

the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first.

What is vapor pressure?

the pressure caused by the collision of particles in a vapor with the walls of a container

What is evaporation?

the process that changes a substance from a liquid to a gas at temperatures below the substance's boiling point

What is pressure?

the result of a force distributed over an area

What is a liquid?

the state of matter in which a material has a definite volume but not a definite shape

What is a gas?

the state of matter in which a material has neither a definite shape nor a definite volume

What is a solid?

the state of matter in which materials have a definite shape and a definite volume