Heat and Temperature

What is Heat??

Heat = Thermal Energy!!

Thermal Energy = the total energy of all of the particles in a material or object.

Throughout the ages people have invented a variety of devices to help create and capture heat for use.

Topic 1: Using Energy from Heat

What are some ways that we use heat? Cook food Warm buildings Dry clothes

What are some ways Thermal Energy has been used throughout history?

Development of Heat Technologies

What heat technologies can you think of that have been developed through-out time? Why have they changed?

Examples….

Devices to generate, transfer, control or remove heat

Heat = Thermal energy

Can you think of any examples of devices that generate, transfer, control or remove heat?

Topic 2: Measuring Temperature

Thermometer: Mechanical or electrical device for measuring temperature. Early thermometer was invented by Galileo.

Scale: A series of equally measured sections that are marked and numbered for use in measurement.

Celsius Scale

Celsius Scale: Most commonly used in Canada. Unit of temperature is called a degree. Based on the boiling and freezing points of water.

Boiling Point: The temperature at which water boils. 100o C at sea level.

Freezing Point: The temperature at which water freezes. 0o C at sea level.

Another Scale…

Kelvin is another way of measuring temperature.

Scientists use Kelvin to explain the behaviour of gases.

“Absolute Zero” is measured in Kelvin – which is the coldest possible temperature

0 Kelvin = -273 ºC

Right Device for the Job

Each thermometer has a sensor – a material which is affected by changes in the environment (such as temperature)

The sensor produces a signal (information about temperature, such as an electrical current) which affects a responder (a pointer, light or other mechanism that uses the signal in some way)

The Thermocouple

Wires made up of two different metals are twisted together.

When the wire tips are heated, a small electric current is generated

The amount of current depends on the temperature.

They can measure higher temperatures than thermometers.

The electric current can be used to turn switches on or off if the temperature changes.

Used in kilns, diesel engines and industrial furnaces

Bimetallic Strip

Made of two different metals joined together

When the strip is heated one metal expands more than the other

Thus the strip coils more tightly

Movement of the strip can operate a switch that can control furnaces…commonly used in thermostats in homes

Your Brain…(extra)

Your brain has its own temperature sensor.

It monitors your own internal temperature. If the temperature outside changes, the sensor signals your brain to release chemicals that will help your body adjust to normal temperature (37°C)

Continued

Recording Thermometer: A bimetallic strip connected to a writing device and paper which records temperature fluctuations over time.

Infrared Thermogram: Records infrared radiation, (heat sensor) as different colors according to their temperature.

Topic 3: Particle Model of Matter, Temperature and Thermal Energy

Reminder: matter is anything that takes up space

Three most important ideas of the model: All substances are made of particles too small

to see The particles are always in motion The particles have space between them

When motion of particles increases – so does the temperature

When motion of particles decreases – so does the temperature

Temperature indicates the average speed of particle motion in a substance

Glow Stick Demonstration

What will happen to the glow stick when it is placed in hot water?

What will happen to the glow stick when it is placed in cold water?

Energy

Energy is the ability to do work – in other words to cause change

In order for something to change, there must be a transfer of energy from one thing to another

Ex. Charged batteries run your iPod, dead batteries would not

Thermal Energy

Energy associated with hot objects

What gives off thermal energy?                                      

What Energy is…and is not

Energy is not a substance. It cannot be weighed It does not take up space Energy describes a condition

Law of Conservation of Energy: Energy cannot be created or destroyed. It can only be transformed from one type to another

or passed from one object to another

Temperature vs. Thermal Energy

Temperature = A measure of the average energy of the particles in a material.

Thermal Energy = The total energy of all the particles in a material.

What is the difference??

Topic 4: Expansion and Contraction

Contract: Decrease in volume Expand: Increase in volume

Temperature changes cause things to expand and contract

Heated – usually causes expansion Cooled – usually causes contraction

Usually more drastic in gases, then liquids then solids

Topic 5: The Particle Model and Changes of State

Heat Capacity: Amount of thermal energy that warms or cools the object by one degree Celsius.

Specific Heat Capacity: Amount of thermal energy that warms or cools one gram of a material by one degree Celsius.

Sample Specific Heat Capacity Table

Solids

Solids have definite shape and volume Cannot be compressed into smaller objects

When solids are heated – they expand When solids are cooled – they contract

Liquids

Liquids have definite volume but no shape Cannot be compressed (meaning if I have 1

litre of coke, I cannot make it fit into a pop can)

When liquids are heated – they expand When liquids are cooled – they contract

Gases

Have no definite shape or size Can be compressed

When heated, gases – expand When cooled, gases - contract

Changes of State

Definitions:

Define, in your notes, each of the following: Melt Freeze Evaporate Condense Sublimation

Continued

Evaporative Cooling: A process in which the faster moving particles on the surface of a liquid evaporate and escape into the air, the slower ones are left behind creating a lower average kinetic energy (cooling it)

Particles are more or less organized when they are hot or cold????

Phase Changing

During a change from solid to liquid or liquid to gas the average temperature does not change even though heat is being added, the name for the heat that is added is latent heat.

Topic 6: Transferring Energy

There are 3 main ways to transfer energy

1) Radiation 2) Conduction 3) Convection

***See handout***

Transferring Energy Continued

Energy Source: An object or material that can transfer its energy to other objects.

Radiation: The transfer of energy without any movement of matter.

Radiant Energy: (a.k.a. EMR) Energy that is transferred by radiation.

Radiant Energy

All forms of radiant energy share several characteristics:

- They behave like waves

- They can be absorbed and reflected by objects

- They travel across empty space at the same high speed of 300,000 km/s

Conduction and Insulation

Thermal Conduction: The process of transferring thermal energy through direct collisions between particles.

Examples of good conductors???

Heat Insulators: Are very poor conductors

Examples???

Topic 7: Sources of Thermal Energy

Energy appears in many forms

Potential Energy: Stored energy

E.g. elastic pulled back and ready to be shot.

Kinetic Energy: Energy of motion

Examples??

Chemical Energy

Stored chemical energy is released in the form of thermal energy when it is burned.

Electrical Energy Electricity

Example: hydro-electric dams – falling water is changed to electrical energy

Geothermal Energy Energy that we get from the Earth’s interior

Solar Energy

Energy from the sun

Passive Solar Heating

Uses materials in the structure to absorb, store, and release solar energy. Example: a wall of

windows

Active Solar Energy

Uses mechanical devices to distribute stored thermal energy Example: fans

Solar Collectors – use stored water or air on the roof, heats it, and then pumps it through the building

Wind Energy

Moving air Is a result of solar

energy – as the sun heats the air, the warmer air rises and cools off. Cooler air falls, creating a convection current – this forms wind

Fossil Fuels

Chemicals made from plants and animals that died and decomposed millions of years ago and have preserved deep underground.

Energy Converters Energy can be converted into another form.

For example a candle can convert chemical energy into heat and light energy.

Candles are energy converters (devices which convert or change energy from one form to another.)

Other examples????

Renewable Resources

Definition:

Renewable resources are a natural resource that grow at about the same rate they are used up.

Non-Renewable Resource

Definition:

A resource which is limited in supply and cannot be replaced once it is used.

Renewable Resources in Alberta

Examples: Trees (Forestry) Wind (Wind Farms) Agriculture ( One of the biggest crop

producers in Canada) Water (Dams and water conservation) Solar ( Solar Panels and Solariums)

Non-Renewable Resources in Alberta

Examples: Oil (Oil Wells) Natural Gas (Pipelines across the

province) Coal (Mining in Alberta)

Positive and Negative Effects On Our Environment

Positive (Renewable) Plentiful Non-polluting Low cost to acquire Cogeneration

Negative (non-renewable)

Polluting – greenhouse gases, thermal pollution

Expensive Can be rare Not plentiful

Greenhouse Gases – do not write down

Even though carbon dioxide occurs naturally in the environment (we breathe out CO2 and plants require CO2), it, like anything is only good in moderation. When there is too much CO2 in the air, heat from Earth is unable to escape into space because it is trapped by greenhouse gases (which have a lot of CO2 in them) – scientist believe that this leads to GLOBAL WARMING

Global Warmingdo not write down

When there is an increase in CO2 and greenhouse gases are trapping thermal energy – the Earth’s temperature increases rapidly. A few degrees doesn’t seem to affect us much, but to the Earth, it can make a huge difference. It can change climate zones, plant growing abilities, dry up rivers and lakes, and even melt polar ice caps….What are some effects on the surrounding environments if these things happen?

Cogeneration

Sometimes negative effects can be turned into more positive effects – cogeneration uses waste from thermal pollution to produce electricity or uses the waste to heat buildings.

FACT: when fuel burns in a thermo-electric power plant, only about 1/3 of its energy is converted into electricity – cogeneration is efficient because it uses some of the remaining 2/3 of energy

The Three Important Renewable Resources to me and Why?

1. Water: Very important to me since I need water to survive. Water is a very good way to generate energy so that I may have electricity in my home.

2. Agriculture: It is the most important to me since I need food to live. It provides me with produce to eat and clothes that I may wear.

Continued

3. Sun: The sun gives me energy to go to school everyday. It provides me with light so that I am not always walking around in the dark. It also makes things grow. The best part is that you can capture the sun and turn it into energy that can be used.

Renewable Resources

Lab Activity…

How else do energy resources affect our environment?

In this lab we will look at how renewable resources and our environment are affected by pollution – specifically OIL SPILLS

Topic 8: Conserving Our Fossil Fuel Resources

Insulate homes and water lines Reduce the amount of energy we use Install a programmable thermostat Carpool

Others????