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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 Matter 25.3 Heat and Thermal Energy. Chapter 25 Objectives.

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unit 8 chapter 25
Unit 8, Chapter 25

CPO Science

Foundations of Physics

unit 8 matter and energy
Unit 8: Matter and Energy

Chapter 25 Energy, Matter, and Atoms

  • 25.1 Matter and Atoms
  • 25.2 Temperature and the Phases of Matter
  • 25.3 Heat and Thermal Energy
chapter 25 objectives
Chapter 25 Objectives
  • Describe the relationship between atoms and matter.
  • 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 temperature.
  • 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
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?

25.1 Matter and Atoms

*Students read Section 25.1 AFTER Investigation 25.1

25 1 matter and atoms6
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
25.1 Brownian Motion
  • A large floating dust speck moves smoothly because it is much larger than a particle of water.
  • A tiny dust speck shows Brownian motion because of collisions with particles of water.
25 1 size of atoms
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 thick.
25 1 classification of matter
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
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
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 (uranium).
25 1 elements13
25.1 Elements
  • At the time of this writing, scientists have created elements 93 to 116 in research laboratories.
  • We don’t find much of elements 93 to 116 in nature because all of these elements are radioactive and break down into other elements.
25 2 temperature and the phases of matter
Key Question:

What is temperature?

25.2 Temperature and the Phases of Matter

*Students read Section 25.2 AFTER Investigation 25.2

25 2 temperature and the phases of matter16
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
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 200°C for 45 minutes.
  • At what temperature should you set your oven, which reads temperature in Fahrenheit?
25 2 temperature and the phases of matter18
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 matter19
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 matter20
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 lower.
  • Technically, we believe atoms never stop moving completely.
  • Figuring out what happens when atoms are cooled to absolute zero is an area of active research.
25 2 temperature and the phases of matter21
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
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.
25 2 phase changes
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 time.
25 2 change from solid to liquid
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
25.2 Energy and Heat of Fusion

Heat of Fusion

(J/kg)

E = mhf

Heat energy (J)

Mass (kg)

25 2 calculate energy
25.2 Calculate Energy
  • How many joules does it take to melt a 30 gram ice cube at 0°C?
25 2 evaporation
25.2 Evaporation
  • Evaporation occurs when molecules go from liquid to gas at temperatures belowthe 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 away.
25 2 condensation
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
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 of vaporization
25.2 Energy and Heat ofVaporization

Heat of

Vaporization

(J/kg)

E = mhv

Heat energy (J)

Mass (kg)

25 2 calculate energy32
25.2 Calculate Energy
  • A steam iron is used to remove the wrinkles from clothes.
  • 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?

25.3 Heat and Thermal Energy

*Students read Section 25.3 AFTER Investigation 25.3

25 3 heat and thermal energy34
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 energy35
25.3 Heat and Thermal Energy
  • Imagine heating a cup of coffee to a temperature of 100°C.
  • Next think about heating up 1,000 cups of coffee to 100°C.
  • The final temperature is the same in both cases but the amount of energy needed is very different.
25 3 heat and thermal energy36
25.3 Heat and Thermal Energy
  • Heat is what we call thermal energy that is moving.
  • 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 chemistry.

Heat flows from the hot coffee to the cooler air in the room.

25 3 specific heat
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 heat38
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
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
25.2 Calculate Heat
  • One kilogram of water is heated in a microwave oven that delivers 500 watts of heat to the water.
  • One watt is a flow of energy of one joule per second.
  • If the water starts at 10°C, how much time does it take to heat up to 100°C?
26 3 first law of thermodynamics
26.3 First Law of Thermodynamics
  • Energy loss is equal to energy gain.