Section 1 Temperature
• Describe how temperature relates
to kinetic energy.
• Compare temperatures on different
temperature scales.
• Give examples of thermal
expansion.
• Temperature is a measure of kinetic
energy.
• Kinetic energy is the energy of motion.
All moving objects have kinetic energy.
• Kinetic energy of an object depends on
the object’s mass and speed.
• All matter is made of atoms or
molecules that are always moving.
• The faster the particles move, the more
kinetic energy they have.
• The more kinetic energy an object has,
the higher the temperature of the
object.
• The gas particles on the right have
more kinetic energy than those on
the left. So, the gas on the right is at
a higher temperature.
• Motion in matter is random, so each
particle has a different amount of kinetic
energy.
• An object’s temperature is the average
kinetic energy of the particles in the
object.
• Thermometers can measure temperature
because of thermal expansion.
• Thermal expansion means that when a
substance’s temperature increases, its
particles move faster and spread out –
creating more volume (expansion).
• The Celsius scale is the most widely used
temperature scale.
• The Fahrenheit scale is the one we use in
the US.
• The Kelvin scale is the official SI
temperature scale.
–The lowest temperature on the Kelvin scale
is 0 K, which is called absolute zero.
• Temperature is represented by
different numbers on the three
temperature scales.
• Expansion Joints on Highways
–Hot weather can make a bridge expand as
the bridge expands, it is in danger of
breaking.
• Expansion joints keep segments of the
bridge apart so that they have room to
expand without the bridge breaking.
•
Bimetallic Strips in Thermostats are
made of two metals stacked in thin
strips. The metals expand at
different rates, a strip coils and
uncoils in response to changes in
temperature, as shown below.
Section 2 What is Heat?
• Define heat as thermal energy
transferred between objects at
different temperatures.
• Compare conduction, convection,
and radiation.
• Use specific heat capacity to
calculate heat.
• Heat is the energy transferred between
objects that are at different
temperatures.
• Energy is always transferred from the
object that has the higher temperature
to the object that has the lower
temperature.
• Heat is transferred in the form of thermal
energy.
–Thermal energy - total kinetic energy of a
substance.
• Thermal energy depends on temperature
and on how much of a substance there is.
• Thermal Equilibrium – when objects that
are touching reach the same
temperature
• When objects are at thermal
equilibrium no net change in the
thermal energy of either one occurs.
•
Thermal Conduction - transfer of
thermal energy through direct contact.
–Conduction can also occur within a
substance.
• When particles of a substance touch,
kinetic energy is transferred until the
energy (and temperature) is even
throughout.
• Thermal conductors – substances that
conduct heat well
–Ex: most metals
• Thermal insulators – substances that do
NOT conduct heat well
–Ex: wood and plastic
• Convection - transfer of thermal energy
by the movement of a liquid or a gas.
–Takes place because of density
–Warmer liquids rise, then begin to cool
back down
–Cooler liquid sinks and then begins to
warm back up
–The cycle repeats
• Radiation - transfer of energy by
electromagnetic (EM) waves.
–All objects radiate EM waves.
• Radiation can involve either a transfer
of energy between particles of matter
OR an energy transfer across empty
space.
–Ex: warmth of the sun
• Radiation and the Greenhouse Effect
–Earth’s atmosphere allows the sun’s visible
light to pass through it.
–The atmosphere also traps energy within
its’ gases, too.
• This process is called the greenhouse
effect. Without it, Earth would be a cold,
lifeless planet.
• Global warming concern: if too much
energy is trapped in the atmosphere, the
Earth may become too warm
• Specific Heat - energy needed to change
the temperature of 1 kg of a substance
by 1°C.
–Higher the specific heat, the more energy it
needs to increase its temperature.
• Most metals have lower specific heats.
• Specific heat of water is very high.
• heat (J)  specific heat (J/kg•°C)  mass (kg)
 change in temperature (°C)
• Calculating Heat - When the temperature
increases, the value of heat is positive.
• When the temperature decreases, the value of
heat is negative.
Section 3 Matter and Heat
Essential Questions
• Identify the three states of matter.
• Explain how heat affects matter
during a change of state.
• Describe how heat affects matter
during a chemical change.
• Explain what a calorimeter is used
for.
States of Matter
• State of matter - the physical forms a
substance
–solid, liquid, and gas (and plasma)
• The state of a substance depends on the
speed of its particles, the attraction
between them, and the pressure around
them.
Changes of State
• Changes of State are physical
changes – changes from one state to
another
• Changes of state include freezing
(liquid to a solid), melting (solid to
liquid), boiling and evaporation
(liquid to gas), condensation (gas to
liquid), and sublimation (solid to
gas).
• Temperature is the SAME during a
change of state, whether the
temperature is increasing or
decreasing
Heat and Chemical Changes
Heat is also involved in chemical
changes
• During a chemical change, a new
substance is formed.
•
–Sometimes a chemical change requires heat
• Ex: baking a cake
–Sometimes a change releases energy in the
form of heat
• Ex: wood burning
• Food and Chemical Energy
–Food gives your body energy.
–Energy is released in a chemical reaction
when compounds such as carbohydrates
are broken down in your body.
• The energy is released in chemical
reactions.
• Calorie – unit used to measure the
amount of energy in food
• Calorimeters - a device that measures
heat. The energy lost by one object is
gained by the other object through
thermal energy.
Section 4 - Heat Technology
Essential Questions
• Analyze several kinds of heating
systems.
• Describe how a heat engine works.
• Explain how a refrigerator keeps food
cold.
• List some effects of heat technology on
the environment.
Heating Systems
• Hot–Water Heating - the high specific heat
of water makes it useful for heating systems.
Warm–Air Heating
•Air cannot hold as much energy as
water can.
•Warm–air heating systems are used
in many homes & offices in the U. S.
• Heating and Insulation
–Insulation reduces the transfer of
thermal energy.
–Insulation is used buildings so less
heat passes into or out of the building.
• Solar Heating systems use the sun’s
energy to heat houses and buildings.
Heat Engine
• Heat engine - a machine that transforms
heat into mechanical energy, or work.
• Combustion – how heat engines use fuel
• External Combustion Engines – burns
fuel outside the engine
–Ex: steam engine
• Internal Combustion Engines – burns
fuel inside an engine
–Ex: car engine
–Fuel (gas) is burned inside the engine,
inside the cylinders.
–The cylinders go through a series of steps
to burn the fuel.
• Cooling systems move heat OUT of an area
• Cooling and Energy - The compressor does
the work of cooling by compressing the
refrigerant. The refrigerant is a gas that has a
boiling point below room temperature, which
allows it to condense easily.
• A negative effect of thermal energy is
thermal pollution, the excessive heating
of a body of water.
• Thermal pollution can happen near
large power plants, which are often
located near a body of water
–It can effect the ecosystem in the area