1. Temperature and Heat

2. All Matter is Made of Moving Particles
• All moving objects have kinetic energy
• Objects such as a house or a wooden chair
have kinetic energy because atoms are
constantly in motion, even if the objects are
not changing position

3. The Kinetic Theory of Matter
• The Kinetic Theory of Matter states that all of the
particles that make up matter are constantly in
motion.
– The particles in a solid are not free to move around
very much. They vibrate back and forth and are held
tightly together by the forces of attraction.
– The particles in a liquid move more freely then a solid.
They are sliding around and tumbling over each
other..
– The particles in a gas are far apart and move around
at high speeds. Particles might collide with one
another, but otherwise they do not interact much.

5. Temperature and Kinetic Energy
• Temperature is a measure of the average
kinetic energy of all the particles in an object

6. Temperature and Kinetic Energy
• If a liquid has a high temperature, particles in
the liquid are moving very fast/have a high
average kinetic energy
• If a liquid has a low temperature, particles are
moving more slowly/have a lower average
kinetic energy

8. Temperature and Kinetic Energy
• Temperature depends on both mass and
speed of particles.
• Particles in a metal doorknob do not move as
fast as particles in the air; however, the
particles in a doorknob have more mass than
air particles. Therefore, they can both have
the same temperature.

9. Temperature Scales
• Fahrenheit
• Celsius
• Kelvin

10. Fahrenheit Scale
• Develop in early 1700s by G. David Fahrenheit
• Zero is the lowest temperature that salt water
will freeze
• 32° F is freezing point of pure water
• 212° F is boiling point of pure water
• F scale used in US for surface temperatures

11. Celsius Scale
• Developed in 1700s
• Also called Centigrade scale
• Zero is the freezing point of pure water
• 100 is the boiling point of pure water at sea
level
• A change of 1 C° = 1.8F°
• 1.8 C = F -32

12. Kelvin Scale
• Absolute zero – molecules stop moving
• Lowest possible temperatures
• Zero K = -459° F
• Zero K = -273° C
• °K = °C + 273
• Kelvin scale used for all scientific equations

14. Thermometers
• A thermometer measures temperature
through the variation of some physical
property of material inside the thermometer
• Ex: a mercury or alcohol thermometer can
measure temperature because the liquid
inside the thermometer always expands or
contracts by a certain amount in response to a
change in temperature

15. Thermal Expansion
• The property that makes a liquid-filled
thermometer work is called thermal
expansion.
• All solids, liquids and gases expand when their
temperature increases
• Construction engineers often have to take
thermal expansion into account because steel
and concrete both expand with increasing
temperature

16. Thermal Expansion
• The Gateway Arch in St. Louis is built mostly of steel.
• The final piece of the Arch to be put into place was the
top segment joining the two legs
• The workers sprayed water on the side facing the Sun to
to reduce thermal expansion.
• Once the final segment was in place, engineers made
the connection strong enough to withstand the force of
the expanding material

17. Heat is Different than Temperature
• Heat is the flow of energy from an object at a
higher temperature to an object at a lower
temperature
• Thermal Energy is the total kinetic energy of
the molecules
• Temperature is the average kinetic energy of
the molecules

19. Measuring Heat
• One calorie is the amount of energy needed
to raise temperature of 1 g of water by 1° C
• This means that 1000 calories of food is
enough energy to 1 kilogram of water 1°C

20. Measuring Heat
• The joule (J) is the standard scientific unit in
which energy is measured.
• 1 Calorie = 4.18 joules

21. Specific Heat
• The amount of energy required to raise the
temperature of 1 gram of a substance by 1°C
is the specific heat of that substance.
• Every substance has its own specific heat
– 1 Calorie raises the temperature of 1 g of water by
1° C
– 0.108 Calories raise the temperature of 1 g of
water by 1°C

22. Specific Heat and Mass
• Recall that thermal energy is the total kinetic
energy of all particles in an object
• Thermal energy depends on the object’s mass
• Water in a glass has the same specific heat as
water in a bathtub
• If the water in the bathtub and coffee cup are
the same temperature, the bathtub will have
to release more thermal energy because of its
mass

23. Specific Heat and Mass: Application
• This idea is particularly relevant for large
masses
• For example, Lake Michigan holds 4.92
quadrillion liters of water.
• Because of the high specific heat of water and
the mass of the water in the lake, the
temperature changes very slowly

24. Specific Heat and Mass: Application
• The temperature of the lake affects the
temperatures on its shores
• During spring and early summer, the lake
warms slowly, which helps the nearby land
stay cooler
• During the winter, the lake cools slowly which
helps keep the nearby land warmer
• Temperatures within about 15 miles of the
lake can differ about 6°C (10° F)

26. Energy Moves As Heat in Three Ways
• Recall that heat is always a transfer of energy
of objects at a high temperature to an object
of a lower temperature

27. Conduction
• Conduction is the process that moves energy
from one object to another when they are
touching physically
• Conduction happens any time objects at different
temperatures come into contact with each other
• As long as objects are in contact, conductions
continues until the temperatures are equal

28. Conduction
• Conductors are materials that transfer energy
easily.
• Conductors often have a low specific heat
(metals are generally good conductors)
• A metal pot becomes too hot to touch soon
after the pot is placed on a stove that has
been turned on

29. Conduction
• Other materials, called insulators, are poor
conductors.
• Insulators have high specific heat.
• Examples: Wood, paper, plastic
• A plastic foam cup will not easily transfer energy
by conduction; therefore, they are often used to
keep cold drinks cold or hot drinks hot.

30. Convection
• Convection is the process that transfers
energy by the movement of large particles in
the same direction within a liquid or gas.
• Convection occurs when a cooler, denser mass
of the gas or liquid replaces a warmer, less
dense mass of the gas or liquid by pushing it
upward.

31. Convection
• Convection is a cycle in nature responsible for
most winds and ocean currents. When the
temperature of a region of air increases the
particles in the air spread out and the air
becomes less dense.
– Cooler, denser air flows underneath the warmer, less
dense air, and pushes the warmer air upward
– When this air cools it becomes more dense than the
warmer air beneath it
– The cooled air sinks and moves under the warmer air

32. Convection

33. Convection

34. Radiation
• Radiation is energy that travels as
electromagnetic waves, which include visible
light, microwaves and infrared light.
• The sun is the most significant source of
radiation that you experience on a daily basis;
however, all objects, even you, emit radiation
and release energy to their surroundings

35. Different Materials Are Used to
Control the Transfer of Energy
• Energy is always being transferred between
objects are different temperatures
• It is often important to slow this movement of
energy
• Think-Pair-Share: Think of one situation
where it would be important to slow the
movement of energy.