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									                                        Chapter 3
                                     States of Matter
Section 1 Matter and Energy

• Summarize the main points of the kinetic theory
  of matter.
• Describe how temperature relates to kinetic energy.
• Describe four common states of matter.
• List the different changes of state, and describe how particles behave in each state.
• State the laws of conservation of mass and conservation of energy, and explain how they
  apply to changes of state.

Kinetic Theory
• Here are the main points of the kinetic theory
  of matter:

   • All matter is made of atoms and molecules that act like tiny particles.

   • These tiny particles are always in motion. The higher the temperature of the substance, the
      faster the particles move.

   • At the same temperature, more-massive (heavier) particles more slower than less-massive
      (lighter) particles.

• The states of matter differ physically from
  one another.

   • Particles of a solid, such as iron, are in fixed positions.

   • In a liquid, such as cooking oil, the particles are closely packed, but they can slide past
     each other.

   • Gas particles are in a constant state of motion
     and rarely stick together.

• Solids have a definite shape and volume.

• The structure of a solid is rigid, and the particles have almost no freedom to change position.

   • Crystalline solids have an orderly arrangement of atoms or molecules.
   • Amorphous solids are composed of atoms or molecules that are in no particular order.
• Liquids change shape, but not volume.

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                                        Chapter 3
                                     States of Matter
   • The particles in a liquid move more rapidly than those of a solid—fast enough to overcome the
     forces of attraction between them.

   • The particles in a liquid can slide past each other, flowing freely. Liquids can take the shape of
     the container they are put into.

   • Liquids have surface tension, the force acting at the surface of a liquid that causes a liquid,
     such as water, to form spherical drops.

• Gases are free to spread in all directions.

   • The particles of a gas move fast enough to break away from each other.

   • The space between gas particles can change, so a gas expands to fill the available space.

   • A gas can also be compressed to a
     smaller volume.

• Plasma is the most common state of matter.

   • Plasma is a state of matter that starts as a gas and then becomes ionized.

   • Plasmas conduct electric current, while gases
     do not.

   • Natural plasmas are found in lightning and fire. The glow of a fluorescent light is caused
     by an artificial plasma, created by passing electric currents through gases.

Energy’s Role
• Energy is the capacity to do work.

• Sources of energy can include:

   • electricity, candles, and batteries

   • the food you eat

   • chemical reactions that release heat

• According to the kinetic theory, all matter is made of particles that are constantly in motion.

• Because the particles are in motion, they have
  kinetic energy, or energy of motion.

• Thermal energy is the total kinetic energy of a substance.

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                                      Chapter 3
                                   States of Matter
   • The more kinetic energy the particles in the object have, the more thermal energy the
     object has.

• Temperature is a measure of average kinetic energy.

   • Unlike total kinetic energy, temperature does not depend on how much of the substance
     you have.

   • For example, a teapot contains more tea than a mug does, but the temperature, or average
     kinetic energy of the particles in the tea, is the same in both containers.

Energy and Changes of State
• A change of state—the conversion of a substance from one physical form to another—is a
  physical change.

• The identity of a substance does not change during
  a change of state, but the energy of a substance does change.

• A transfer of energy known as heat causes the temperature of a substance to change, which
  can lead to a change of state.

• Some changes of state require energy.

   • Evaporation is the change of a substance from a liquid to a gas. Energy is needed to
     separate the particles of a liquid to form a gas.

   • Sublimation is the process by which a solid turns directly to a gas. Sometimes ice
     sublimes to form a gas.

• Energy is released in some changes of state.

   • Condensation is the change of a substance from a gas to a liquid. Energy is released from
     the gas and the particles slow down.

   • Energy is also released during freezing, which is the change of state from a liquid to a

• When a substance loses or gains energy, either
  its temperature changes or its state changes, but
  not both.

Conservation of Mass and Energy
• The law of conservation of mass says that
  mass cannot be created or destroyed.
   • For instance, when you burn a match, the total mass of the reactants (the match and

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                                                  Chapter 3
                                               States of Matter
        oxygen) is the same as the total mass of the products (the ash, smoke, and gases).
• The law of conservation of energy states that
  energy cannot be created or destroyed.
     • For instance, when you drive a car, gasoline releases its stored energy, in the form of heat,
       used to move the car.

Section 2 Fluids

• Describe the buoyant force and explain how it keeps
  objects afloat.

• Define Archimedes’ principle.

• Explain the role of density in an object’s ability to float.

• State and apply Pascal’s principle.

• State and apply Bernoulli’s principle.

Although you may not be familiar with the specific details, you have seen buoyant forces at
work. You know from experience that certain objects float in air or in water. This is because of
the force that pushes, or buoys the object up. This force opposes the weight of the object, which
is always in the downward direction.
Examine each of the drawings shown on the next slide. Then answer the items that follow.
1. Is the buoyant force on the lump of gold greater than, less than, or equal to the gold’s weight?
2. Is the buoyant force on the balloon greater than, less than, or equal to the balloon’s weight?
3. Is the buoyant force on the boat greater than, less than, or equal to the boat’s weight?
4. Is the buoyant force on the submarine greater than, less than, or equal to the submarine’s weight?

• A fluid is a nonsolid state of matter in which the atoms or molecules are free to move past
  each other, as in a gas or liquid.

• Fluids are able to flow because their particles can move past each other easily.

• The properties of fluids allow huge ships to float, divers to explore the ocean depths, and
  jumbo jets
  to soar across the skies.

Buoyant Force

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                                        Chapter 3
                                     States of Matter
• Buoyant force is the upward force exerted on an object immersed in or floating on a fluid.

• Buoyancy explains why objects float.

   • All fluids exert pressure: the amount of force exerted per unit area of a surface.

   • Archimedes’ principle states that the buoyant force on an object in a fluid is an upward
     force equal to the weight of the volume of fluid that the object displaces.

• The volume of fluid displaced by an object placed in a fluid will be equal to the volume of the
  part of the object submerged.

• The figure below shows how displacement works.

• An object will float or sink based on its density.

   • If an object is less dense than the fluid in which it is placed, it will float.

   • If an object is more dense than the fluid in which it is placed, it will sink.

Fluids and Pressure
• Fluids exert pressure evenly in all directions.

   • For example, when you pump up a bicycle tire, air particles are constantly pushing against
     each other and against the walls of the tire.

• Pressure can be calculated by dividing force by the area over which the force is exerted:

Pascal’s Principle
• Pascal’s principle states that a fluid in equilibrium contained in a vessel exerts a pressure of
  equal intensity in all directions.

• Mathematically, Pascal’s principle is stated as
  p1 = p2, or pressure1 = pressure2.

Math Skills
Pascal’s Principle A hydraulic lift, shown in the figure below, makes use of Pascal’s principle,
  to lift a 19,000 N car. If the area of the small piston (A1) equals 10.5 cm2 and the area of the
  large piston (A2) equals 400 cm2 , what force needs to be exerted on the small piston to lift the

1. List the given and unknown values.
   Given:       F2 = 19,000 N
        A1 = 10.5 cm2
        A2 = 400 cm2

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                                              Chapter 3
                                           States of Matter
   Unknown: F1

2. Write the equation for Pascal’s principle.
   According to Pascal’s principle, p1 = p2.

3. Insert the known values into the equation,
   and solve.

• Hydraulic devices are based on Pascal’s principle.
   • Hydraulic devices can multiply forces, as shown in the figure below. Because the pressure
     is the same on both sides of the enclosed fluid, a small force on the smaller area (at left)
     produces a much larger force on the larger area (at right).

Fluids in Motion
• Viscosity is the resistance of a gas or liquid to flow.

• Bernoulli’s principle states that as the speed of a moving fluid increases, the pressure of the
  moving fluid decreases.

    • Bernoulli’s principle is illustrated below: as a leaf passes through a drainage pipe from
      point 1 to point 2, it speeds up, and the water pressure decreases.

Section 3 Behavior of Gases

• Explain how gases differ from solids and liquids.

• State and explain the following gas laws: Boyle’s law, Charles’s law, and Gay-Lussac’s law.

• Describe the relationship between gas pressure, temperature and volume.

The pressure of gas depends on how frequently the particles of gas strike the sides of the container holding the gas.
Use your experience and, after examining each of the pairs of drawings shown below, decide whether you think the
pressure of the contained gas has increased, decreased, or remained unchanged.

2. The gas in the toy balloon expands outward, as shown below. After this expansion, has the pressure of the gas
a. increased?
b. decreased?
c. remained unchanged?

Properties of Gases
• Gases have unique properties. Some important properties of gases are listed below.

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                                          Chapter 3
                                       States of Matter
    • Gases have no definite shape or volume, and they expand to completely fill their container.

    • Gas particles move rapidly in all directions.

    • Gases spread out easily and mix with one another. Unlike solids and liquids, gases are
      mostly empty space.

•   (some important gas properties, continued)

    • Gases have a very low density because their particles are so far apart. Because of this
      property, gases are used to inflate tires and balloons.

    • Gases are compressible.

    • Gases are fluids.

    • Gas molecules are in constant motion, and they
      frequently collide with one another and with the walls of their container.

• Gases exert pressure on their containers.

    • The kinetic theory helps to explain pressure. Helium atoms in a balloon are constantly hitting each
      other and the walls of the balloon, as shown below.

    • Therefore, if the balloon is punctured, the gas will escape with a lot of force, causing the balloon to

Gas Laws
• Boyle’s law states that for a fixed amount of gas at a constant temperature, the volume of the
  gas increases its pressure decreases. Likewise, the volume of a gas decreases as its pressure

    •   Boyle’s law can be expressed mathematically as:
        (pressure1)(volume1) = (pressure2)(volume2) ,
        or P1 V1 = P2 V2

• Charles’s law states that for a fixed amount of gas at a constant pressure, the volume of the
  gas increases as its temperature decreases. Likewise, the volume of a gas decreases as its
  temperature increases.

    •   As shown below, if the gas in an inflated balloon is cooled (at constant pressure), the gas
        will decrease in volume and cause the balloon to deflate.

• Gay-Lussac’s law states that the pressure of a gas increases as the temperature increases if
  the volume of the gas does not change.

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                                        Chapter 3
                                     States of Matter
   •   This is why, if a pressurized container that holds gas, such as a spray can, is heated, it may

Math Skills
Boyle’s Law The gas in a balloon has a volume of
  7.5 L at 100 kPa. The balloon is released into the atmosphere, and the gas expands to a
  volume of
  11 L. Assuming a constant temperature, what is the pressure on the balloon at the new

1. List the given and unknown values.
   Given:       V1 = 7.5 L
                P1 = 100 kPa
                V2 = 11 L
   Unknown: P2

2. Write the equation for Boyle’s law, and rearrange the equation to solve for P2.
   P1 V1 = P2 V2

3. Insert the known values into the equation,
   and solve.

Understanding Concepts
1. Which of the following changes of state is exothermic?

   A.   evaporation
   B.   freezing
   C.   melting
   D.   sublimation

2. Which of these statements describes the particles of a liquid?

   F.   Particles are far apart and move freely.
   G.   Particles are close together and vibrate in place.
   H.   Particles are far apart and unable to change location.
   I.   Particles are close together and move past each other easily.
3. As the plunger is depressed, the volume of a syringe filled with helium gas is reduced from
   25 mL to 10 mL. If the initial pressure is 150 kPa, what is
   the final pressure, in kPa, assuming constant temperature?

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                                      Chapter 3
                                   States of Matter
Answer: 375 kPa

Reading Skills
Read the passage below. Then answer the question.

   If the temperature in a citrus orchard drops below
   –2°C for several hours, the fruit will freeze and be destroyed. Citrus growers spray tiny
   droplets of water to protect the crop if a freeze is predicted. Protection comes from the heat
   released as the heated water cools. However, much of the heat that protects trees from
   freezing is released as the water freezes.

4. Based on the energy changes that occur when materials change state, determine how water
   freezing on the fruit can protect it from becoming too cold?

Answer: The process of freezing is exothermic, so heat is generated as water changes from the
   liquid to the solid state. This heat protects the tree as the water freezes on it.

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