Matter and Energy
Unit 4: Matter and Energy
Chapter 9: Matter and Energy
 9.1
Matter, Temperature and Pressure
 9.2
What is Heat?
 9.3
Heat Transfer
9.1 Investigation: Temperature and Heat
Key Question:
How is temperature different
from heat?
Objectives:
Describe the relationship between temperature and heat.
 Apply the heat equation to predict the final temperature of a
mixture.
 Infer that different substances are able to store different
amounts of heat.

Matter and energy
 Greek
philosophers
Democritus and
Leucippus proposed that
matter is made of tiny
particles called atoms.
 Atoms
were an idea that
few believed.
Today we know sugar is made
up of small particles called
molecules and they are
composed of atoms.
The Nature of Matter
Robert Brown first noticed the
jerky motion of tiny particles.

Throwing marbles at a tire
tube moves the tube
smoothly.

Throwing the same marbles
at a foam cup moves the
cup in a jerky way, like
Brownian motion.

Varying the mass and size of
particles that collide can
have different effects.
Atoms
 A single
atom is the smallest particle that retains
the chemical identity of the element.
Elements
 An
element is a pure
substance that cannot be
broken down into other
substance by chemical or
physical means.
 All
of the matter you are ever
likely to experience is made
from one or more elements in
nature.
Atoms
 Sodium
atoms are different from carbon, aluminum,
oxygen or hydrogen atoms.
 They
have different masses.
Compounds and elements
 Compounds
are two or more different
elements chemically bonded together.
Examples of compounds

Compounds contain
more than one type
of atom joined
together.
Molecules
 A molecule
is a group of two or more atoms
joined together chemically.
Mixtures
 Many
substances you
encounter are a mixture
of different elements and
compounds.
How many
atomsmolecules
are in
How many
are
this mixture?
in this mixture?
Elements, compounds, and mixtures
Can you distinguish between the atoms and molecules in these
images?
Particles of matter and temperature
 Atoms
are in constant motion,
even in a solid object.
 Particles
in a solid are
connected by bonds that act
like springs.
Particles of matter and temperature
 Temperature
measures the kinetic energy per
molecule due to random motion.
Intermolecular forces and temperature
 Neighboring
atoms and
molecules are attracted
through intermolecular
forces.
 The
strength of the
intermolecular forces
determines whether matter
exists as a solid, liquid, or
gas at any given
temperature.
The phases of matter
 A solid
holds its shape and
does not flow.
 The
molecules in a solid
vibrate in place, but on
average, don’t move far from
their places.
The phases of matter
 A liquid
holds its
volume, but does not
hold its shape—it flows.
 Liquids
flow because the
molecules can move
around.
The phases of matter
 A gas
flows like a liquid, but
can also expand or contract
to fill a container.
 A gas
does not hold its
volume.
 The
molecules in a gas
have enough energy to
completely break away from
each other.
Melting and boiling
 The
melting point is the temperature at which
a substance changes from a solid to a liquid.
Melting and boiling
 The
temperature at which a liquid becomes a
gas is called the boiling point.
Phase change
 As
energy is add to the
system, the
intermolecular forces
grow weaker and the
substance changes
phase.
Temperature scales
 There
are two common
temperature scales.
 On
the Fahrenheit scale,
water freezes at 32
degrees and boils at 212
degrees.
 The
Celsius scale divides
the interval between the
freezing and boiling points
of water into 100 degrees.
Converting between temperature scales
A 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
uses the Fahrenheit scale?
1.
Looking for: … temperature in °F.
2.
Given: … temperature (200C).
3.
Relationships: Use: TF = 9/5 TC + 32
4.
Solution: TF = (9/5)(200 °C) + 32 = 392 °F
Absolute zero
 Absolute
zero is -273°C.
 You
cannot have a temperature lower than
absolute zero.
 Think
of absolute zero as the temperature at which
atoms are “frozen.”
Plasma
 In
the plasma phase, matter
becomes ionized as electrons
are broken loose from atoms.
 The
Sun is made of plasma,
as is most of the universe,
including the Eagle nebula.
Particles of matter and pressure
 Like
temperature, pressure is related to the motion
of particles.
 Pressure
liquids.
is associated with fluids—gases and

According to Newton’s third
law, a equal and opposite
forces are exerted by particles
in a pitcher .

The reaction force is what
creates the pressure acting on
the inner surface of the pitcher.
Unit 4: Matter and Energy
Chapter 9: Matter and Energy
 9.1
Matter, Temperature and Pressure
 9.2
What is Heat?
 9.3
Heat Transfer
9.2 Investigation: Energy and Phase Changes
Key Question:
How is energy involved when
matter changes phase?
Objectives:

Compare and contrast the properties of matter in the solid,
liquid, and gas phases.

Describe what happens, in terms of energy, when matter
changes phase.
What is heat?
 Heat
and temperature are
related, but are not the
same thing.
 The
amount of thermal
energy depends on the
temperature but it also
depends on the amount of
matter you have.
Units of heat and thermal energy
 The
metric unit for
measuring heat is the
joule.
 This
is the same joule
used to measure all
forms of energy, not just
heat.
Heat and thermal energy
 Thermal
 One
energy is often measured in calories.
calorie is the amount of energy it takes to raise
the temperature of one milliliter of water by one
degree Celsius.
Specific heat
 The
specific heat is a
property of a substance
that tells us how much
heat is needed to raise
the temperature of one
kilogram of a material
by one degree Celsius.
The apple filling in the pie has a higher specific heat than the
crust. How do you know?
Specific heat of various materials
 If
the specific heat is high
(like water), then the
temperature will change
relatively slowly because
each degree of change
takes more energy.
Knowing the specific heat of a material tells you how quickly
the temperature will change as it gains or loses energy.
Calculating heat
How much heat is needed to raise the temperature
of a 250-liter hot tub from 20°C to 40°C? The
specific heat of water is 4,184 J/kg·°C. (Hint: 1 L of
water has a mass of 1 kg.)
1.
Looking for: … heat.
2.
Given: … tub temp. change (20 °C), tub volume (250 L) and
you know the specific heat of water.
3.
Relationships: Use: E = mCp(T2 – T1)
4.
Solution: E = (250L × 1kg/L) × 4,184 J/kg°C (20°C) = 20,920,000 J
Why is specific heat different for
different materials?
 Temperature
measures the average kinetic energy
per particle.
 Energy
that is divided between fewer particles
means more energy per particle, and therefore more
temperature change.
 In
general, materials made up of heavy atoms or
molecules have low specific heat compared with
materials made up of lighter ones.
Unit 4: Matter and Energy
Chapter 9: Matter and Energy
 9.1
Matter, Temperature and Pressure
 9.2
What is Heat?
 9.3
Heat Transfer
Heat transfer


Thermal energy flows from higher temperature
to lower temperature. This process is called
heat transfer.
There are three ways heat flows:
— heat conduction,
— convection, and
— thermal radiation.
Heat conduction
 Heat
conduction is the
transfer of heat by the
direct contact of particles
of matter.
 Conduction
Where is the heat energy
conducted to and from in
this system?
occurs
between two materials at
different temperatures
when they are touching
each other.
Thermal equilibrium
 Thermal
equilibrium occurs when two bodies have
the same temperature.
 No
heat flows in thermal equilibrium because the
temperature is the same in the two materials.
Thermal conductors and insulators
 Materials
that conduct heat
easily are called thermal
conductors and those that
conduct heat poorly are called
thermal insulators.
Is a down coat a
conductor or an
insulator?
Convection
 Convection
is the transfer of heat through the
motion of matter such as air and water.
 The
hot water at the bottom of the pot rises to the
top and replaces the cold water.
Convection
 Convection
is mainly what distributes heat
throughout a room.
Thermal radiation
 Heat
from the Sun is
transferred to Earth by
thermal radiation.
 All
the energy the Earth
receives from the Sun
comes from thermal
radiation.
 The
higher the temperature
of an object, the more
thermal radiation it emits.
Thermal radiation

Thermal radiation is also
absorbed by objects.

The amount of thermal radiation
absorbed depends on the
surface of a material.

Silvered or mirrored surfaces
reflect thermal radiation.

Dark surfaces absorb most of
the thermal radiation they
receive.
The rate of heat transfer
 Heat
transfer always occurs
from hot to cold until thermal
equilibrium is reached.
 The
rate of heat transfer is
proportional to the difference
in temperature.
 Heat
flow continues as long
as there is a temperature
difference.
Gear up for a Space Walk

Earth’s atmosphere does a lot
more to help humans maintain
homeostasis (internal balance)
than just providing oxygen.

It keeps global temperatures
within a narrow range, shields
us from harmful radiation,
breaks up most meteoroids, and
provides the pressure our
bodies need to function
properly.