Chapter 9:
Heat and States of Matter
Section 1: Temperature and Thermal Energy
Temperature and Thermal Energy
1
Kinetic Theory of Matter
• The motion of the particles in matter is
described by KINETIC THEORY of matter.
• Matter is
composed of
particles that
are atoms,
molecules, or
ions that always
are in random
motion.
Temperature and Thermal Energy
1
Temperature
• The TEMPERATURE of a
substance is a measure of the average
kinetic energy of its particles.
• The SI unit for temperature is the
KELVIN (K).
Temperature and Thermal Energy
1
Temperature
• Commonly used temperature scales are
the Celsius scale and the Fahrenheit scale.
Conversion Equations:
°C = (5/9)(°F – 32)
°F = 1.8 (°C) + 32
Temperature and Thermal Energy
1
Temperature
Using Conversion Equations:
Room temperature is considered to be 22 °C
What is this temperature in °F?
°F = 1.8 (°C) + 32°
°F = 1.8 (22°) + 32°
°F = 39.6° + 32°
°F = 71.6 °F
Temperature and Thermal Energy
1
Temperature
Using Conversion Equations:
Water boils at 212 °F at standard temperature and pressure
What is this temperature in °C?
°C = (5/9) (°F – 32)
°C = (5/9)(212° – 32)
°C = (5/9) (180°)
°C = 100°F
Temperature and Thermal Energy
1
Thermal Energy
• The sum of the kinetic and potential energies of
all the particles in an object is the THERMAL
ENERGY of the object.
• The increase in an
object’s speed
doesn’t affect the
random motion of
its particles, so it
doesn’t affect its
thermal energy.
Temperature and Thermal Energy
1
Heat
• HEAT is thermal energy that flows from
something at a higher temperature to
something at a lower temperature.
• Heat is a form of energy, so it is
measured in joules.
Temperature and Thermal Energy
1
Specific Heat
• The amount of thermal
energy needed to raise
the temperature of 1 kg
of some material by 1°C
is called the SPECIFIC
HEAT of the material.
• Specific heat is
measured in joules
per kilogram per
degree Celsius.
Temperature and Thermal Energy
1
Changes in Thermal Energy
Change in Thermal Energy (J) =
mass (Kg) x change in temperature (C) x specific heat ( J/Kg°C)
Q = m (Tf – Ti) C
J = (Kg)(°C ) J
Kg °C
Temperature and Thermal Energy
1
Measuring Specific Heat
• The specific heat
of a material can
be measured using
a device called a
CALORIMETER.
• In a calorimeter, a
heated sample
transfers thermal
energy to a known
mass of water.
Temperature and Thermal Energy
1
Measuring Specific Heat
• The thermal
energy released
by the sample is
equal to the
thermal energy
absorbed by the
water.
Section Check
1
Question 1
How is temperature related to kinetic energy?
Section Check
1
Answer
Temperature is a measure of the average kinetic
energy of the particles in an object or material.
As the temperature increases, the average speed
of the particles increases.
Section Check
1
Question 2
How does thermal energy differ from
kinetic energy?
Answer
Thermal energy is the sum of the kinetic and
potential energy of all the particles in an object.
Section Check
1
Question 3
The amount of heat that is needed to raise the
temperature of 1 kg of a material by 1º C is
called the __________ of the material.
A.
B.
C.
D.
density
mass
specific heat
thermal energy
Section Check
1
Answer
The answer is C. Specific heat is measured in
joules/kilogram °C.