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Unit 8, Chapter 25


CPO Science Foundations of Physics Unit 8, Chapter 25 Unit 8: Matter and Energy 25.1 Matter and Atoms 25.2 Temperature and the Phases of Matter 25.3 Heat and ... – PowerPoint PPT presentation

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Title: Unit 8, Chapter 25

Unit 8, Chapter 25
CPO Science Foundations of Physics
Unit 8 Matter and Energy
Chapter 25 Energy, Matter, and Atoms
  • 25.1 Matter and Atoms
  • 25.2 Temperature and the Phases of
  • 25.3 Heat and Thermal Energy

Chapter 25 Objectives
  • Describe the relationship between atoms and
  • Find an element in the periodic table.
  • Identify the differences between elements,
    compounds, and mixtures.
  • Convert temperatures between Fahrenheit, Celsius,
    and Kelvin scales.
  • Understand the concept of absolute zero
  • Describe the phases of matter and explain solid,
    liquid, and gas in terms of energy and atoms.
  • Describe the concepts of heat and thermal energy
    and apply them to real-life systems.
  • Perform basic calculations with specific heat.

Chapter 25 Vocabulary Terms
  • atom
  • compound
  • element
  • mixture
  • molecule
  • periodic table
  • Kelvin
  • Celsius
  • thermometer
  • Fahrenheit
  • specific heat
  • temperature
  • calorie
  • absolute zero
  • random
  • melting point
  • heat of vaporization
  • boiling point
  • evaporation
  • ionized
  • condensation
  • thermal energy
  • relative humidity
  • British thermal unit (BTU)
  • heat
  • solid
  • plasma
  • liquid
  • heat of fusion
  • gas

25.1 Matter and Atoms
  • Key Question
  • What are the properties of different elements?

Students read Section 25.1 AFTER Investigation
25.1 Matter and Atoms
  • We have partial answers to these three questions
    for all types of matter
  • What is the smallest piece of matter?
  • Why can the same kind of matter assume different
    forms, like solid or liquid?
  • How can one kind of matter (like wood) turn into
    another kind of matter with very different
    properties (like ashes)?

25.1 Brownian Motion
  • A large floating dust speck moves smoothly
    because it is much larger than a particle of
  • A tiny dust speck shows Brownian motion because
    of collisions with particles of water.

25.1 Size of atoms
  • The head of a pin contains more than 1020 atoms.
  • A sheet of thin aluminum foil is 200,000 atoms

25.1 Classification of matter
  • A molecule is a group of two or more atoms that
    are joined together.
  • Most matter you encounter is made of molecules,
    or mixtures of molecules.

25.1 First theory of matter
  • The ancient Greeks proposed that all matter was
    made of four fundamental elements
  • air, fire, water, and earth.

25.1 Elements
  • Today we know that nearly all the matter in the
    world is made from 92 different elements.
  • The periodic table shows the elements in order
    from atomic number 1 (hydrogen) to number 92

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25.1 Elements
  • At the time of this writing, scientists have
    created elements 93 to 116 in research
  • We dont find much of elements 93 to 116 in
    nature because all of these elements are
    radioactive and break down into other elements.

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25.2 Temperature and the Phases of Matter
  • Key Question
  • What is temperature?

Students read Section 25.2 AFTER Investigation
25.2 Temperature and the Phases of Matter
  • In the Fahrenheit scale, water freezes at 32
    degrees and boils at 212 degrees
  • The Celsius scale divides the difference between
    the freezing and boiling points of water into 100
    degrees (instead of 180).

25.2 Converting temperatures
  • A friend in Paris sends you a recipe for a cake.
  • The French recipe says to bake the cake at a
    temperature of 200C for 45 minutes.
  • At what temperature should you set your oven,
    which reads temperature in Fahrenheit?

25.2 Temperature and the Phases of Matter
  • All thermometers are based on some physical
    property (such as color or volume) that changes
    with temperature.
  • A thermistor is a device that changes its
    electrical resistance as the temperature changes.
  • A thermocouple is another electrical sensor that
    measures temperature.

25.2 Temperature and the Phases of Matter
  • Temperature measures the kinetic energy per atom
    due to random motion.
  • Random motion is motion that is scattered equally
    in all directions.
  • In pure random motion the average change in
    position is zero.

25.2 Temperature and the Phases of Matter
  • When the temperature gets down to absolute zero,
    the atoms are said have the lowest energy they
    can have and the temperature cannot get any
  • Technically, we believe atoms never stop moving
  • Figuring out what happens when atoms are cooled
    to absolute zero is an area of active research.

25.2 Temperature and the Phases of Matter
  • The Kelvin temperature scale is useful for many
    scientific calculations because it starts at
    absolute zero.
  • The Kelvin scale is used because it measures the
    actual energy of atoms.
  • A temperature in Celsius measures only the
    relative energy, relative to zero Celsius.

25.2 Phases of Matter
  • The three most common phases of matter are called
    solid, liquid, and gas.
  • At temperatures greater than 10,000 K the atoms
    in a gas start to break apart.
  • In the plasma state, matter becomes ionized.

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25.2 Phase changes
  • When thermal energy is added or subtracted from a
    material, either the temperature changes, or the
    phase changes, but usually not both at the same

25.2 Change from solid to liquid
  • The melting point is the temperature at which a
    material changes phase from solid to liquid.
  • Melting occurs when the kinetic energy of
    individual atoms equals the attractive force
    between atoms.
  • The heat of fusion is the amount of energy it
    takes to change one kilogram of material from
    solid to liquid or vice versa.

25.2 Energy and Heat of Fusion
Heat of Fusion (J/kg)
E mhf
Heat energy (J)
Mass (kg)
25.2 Calculate Energy
  • How many joules does it take to melt a 30 gram
    ice cube at 0C?

25.2 Evaporation
  • Evaporation occurs when molecules go from liquid
    to gas at temperatures below the boiling point.
  • Evaporation takes energy away from a liquid.
  • The average energy of the molecules left behind
    is lowered.
  • Evaporation cools the surface of a liquid because
    the fastest molecules escape and carry energy

25.2 Condensation
  • Condensation occurs when molecules go from gas to
    liquid at temperatures below the boiling point.
  • Condensation raises the temperature of a gas
    because atoms in a gas have more energy than
    atoms in a liquid.
  • When air is saturated, it means the processes of
    evaporation and condensation are exactly balanced.

25.2 Change from liquid to gas
  • The boiling point is the temperature at which the
    phase changes from liquid to gas.
  • Just as with melting, it takes energy for an atom
    to go from liquid to gas.
  • The heat of vaporization is the amount of energy
    it takes to convert one kilogram of liquid to one
    kilogram of gas.

25.2 Energy and Heat ofVaporization
Heat of Vaporization (J/kg)
E mhv
Heat energy (J)
Mass (kg)
25.2 Calculate Energy
  • A steam iron is used to remove the wrinkles from
  • The iron boils water in a small chamber and vents
    steam out the bottom.
  • How much energy does it require to change
    one-half gram (0.0005 kg, or about half a
    teaspoon) of water into steam?

25.3 Heat and Thermal Energy
  • Key Question
  • What is the relationship between heat,
    temperature, and energy?

Students read Section 25.3 AFTER Investigation
25.3 Heat and Thermal Energy
  • Temperature is NOT the same as thermal energy.
  • Thermal energy is energy stored in materials
    because of differences in temperature.
  • The thermal energy of an object is the total
    amount of random kinetic energy for all the atoms
    in the object.
  • Remember, temperature measures the random kinetic
    energy of each atom.

25.3 Heat and Thermal Energy
  • Imagine heating a cup of coffee to a temperature
    of 100C.
  • Next think about heating up 1,000 cups of coffee
    to 100C.
  • The final temperature is the same in both cases
    but the amount of energy needed is very different.

25.3 Heat and Thermal Energy
  • Heat is what we call thermal energy that is
  • The joule (J) is the unit of heat (or thermal
    energy) used for physics and engineering.
  • The calorie is a unit of heat often used in

Heat flows from the hot coffee to the cooler air
in the room.
25.3 Specific Heat
  • The specific heat is the quantity of heat it
    takes to raise the temperature of one kilogram of
    material by one degree Celsius.

25.3 Specific Heat
  • The temperature of gold rises quickly compared
    with water because its specific heat is much less
    than the specific heat of water.

25.2 Heat Equation
Specific heat (J/kgoC)
Heat energy (J)
E mcp(T2-T1)
Change in Temperature (oC)
Mass (kg)
25.2 Calculate Heat
  • One kilogram of water is heated in a microwave
    oven that delivers 500 watts of heat to the
  • One watt is a flow of energy of one joule per
  • If the water starts at 10C, how much time does
    it take to heat up to 100C?

26.3 First Law of Thermodynamics
  • Energy loss is equal to energy gain.

26.3 Second Law of Thermodynamics
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Application The Refrigerator
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