HEAT Chapter Eleven: Heat 11.1 Heat 11.2 Heat Transfer Chapter 11.1 Learning Goals Describe the relationship between heat, temperature, and thermal energy. Identify and use.
Download ReportTranscript HEAT Chapter Eleven: Heat 11.1 Heat 11.2 Heat Transfer Chapter 11.1 Learning Goals Describe the relationship between heat, temperature, and thermal energy. Identify and use.
HEAT
Chapter Eleven: Heat 11.1 Heat 11.2 Heat Transfer
Chapter 11.1 Learning Goals Describe the relationship between heat, temperature, and thermal energy.
Identify and use different units to measure heat.
Explain how the specific heat of different materials can be used to describe changes in temperature and energy.
Investigation 11A Temperature and Heat
Key Question: How are temperature and heat related?
11.1 What is heat?
Heat
is thermal energy that is moving.
Heat flows any time there is a difference in temperature.
Because your hand has more thermal energy than chocolate, thermal energy flows from your hand to the chocolate and the chocolate begins to melt.
11.1 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.
11.1 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.
11.1 Heat and thermal energy Thermal energy is often measured in
calories
. One calorie is the amount of energy it takes to raise the temperature of one milliliter of water by one degree Celsius.
11.1 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.
Knowing the specific heat of a material tells you how quickly the temperature will change as it gains or loses energy.
11.1 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.
Solving Problems How much heat is needed to raise the temperature of a 250-liter hot tub from 20°C to 40°C?
Solving Problems 1.
2.
3.
4.
Looking for: …amount of heat in joules Given: V = 250 L, 1 L of water = 1 kg Temp changes from 20°C to 40°C Table specific heat water = 4, 184 J/kg°C Relationships: E = mC p (T 2 – T 1 ) Solution:
Sig. fig./Sci. not. 20,920,000 J = 2.1 x 10
20,920,000 J
7 J
Chapter Eleven: Heat 11.1 Heat 11.2 Heat Transfer
Chapter 11.2 Learning Goals Compare and contrast various methods of heat transfer.
Differentiate between thermal conductors and thermal insulators.
Explain what it means when objects are in thermal equilibrium.
Investigation 11B The Specific Heat of a Metal
Key Question: What is the identity of an unknown metal sample?
11.2 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
.
11.2 Heat transfer
Heat conduction
transfer of heat by the direct contact of is the particles of matter.
Where is the heat energy conducted to and from in
Conduction occurs between two materials at different temperatures when they are touching each other.
this system?
11.2 Heat transfer
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.
11.2 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?
11.2 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.
11.2 Convection Convection is mainly what distributes heat throughout a room.
11.2 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.
11.2 Thermal radiation Thermal radiation is also
absorbed
by objects.
The amount of thermal radiation absorbed depends on the surface of a material.
Dark surfaces absorb most of the thermal radiation they receive. Silver or mirrored surfaces reflect thermal radiation.
11.2 Heat transfer, winds, and currents
A
thermal
is a convection current in the atmosphere.
When a surface, like a road absorbs solar radiation, it emits energy as heat.
The warmed air molecules gain kinetic energy and rise.
Colder air is forced aside and sinks.
11.2 Thermal radiation There are giant convection currents in Earth’s atmosphere.
The global wind patterns and Earth’s rotation also cause surface ocean currents to move in large circular patterns.
Investigation 11C Mass Determination
Key Question: Can the mass of an object be determined without the use of a balance?
Needed: Efficient Buildings “Green” building design is the term used to describe architecture that is energy-efficient and environmentally friendly .