# TOPIC: Heat AIM: What is heat & how is it measured?

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TOPIC: Heat AIM: What is heat & how is it measured?

What you will learn: Define temp. Explain how thermal energy and temp are related. Calculate the change in thermal energy of an object due to temp change.

Why is it important: Cars, buses, trucks and airplanes could not operate without thermal energy. What is kinetic energy? Review vocab: Kinetic energy: energy an object has due to motion

New Vocab Kinetic theory Kelvin Temp Thermal energy Heat Specific heat

Kinetic Theory of Matter
Matter is made of molecules that are always in motion which collide & transfer their Kinetic Energy

Molecules are always moving which produces heat
The more heat that is contained the faster the molecules move

What are molecules?

Tiny particles that make up matter
Molecules Tiny particles that make up matter

Example: 1 molecule of water = H2O
5 molecules of water

Molecules moving (have KE)

What is heat? Energy caused by internal motion of molecules Energy moves from warm  cooler region

Measure of how hot or cold something is
Temperature Measure of how hot or cold something is Measure of average KE of molecules

Analyzing relationships
If heat is added to an object the molecules move ________, which _________ the Kinetic Energy, which causes the temperature to _________. faster increases increase

Low temp = slower moving
High temp = fast moving

The average kinetic energy of the particles in the soup is greater than the average kinetic energy of the particles in the ice cream.

70°F 70°F The pail of water has fewer molecules in it than the ocean does. Even though they may be the same temperature, the pail of water has less heat than the ocean.

For measuring temperature Tube filled with a fluid such as mercury
Thermometer For measuring temperature Tube filled with a fluid such as mercury

Heated molecules move faster and far apart
Mercury expands & rises up tube

Cooled  molecules slow & move closer together 
Mercury contracts and drops

Heated Liquid level rises Cooled Liquid level drops

Fahrenheit Scale Non-metric temp scale °F

Water freezes = 32°F Water boils = 212°F Human body temp = 98.6°F

Celsius Scale Metric scale °C

Water freezes = 0°C Water boils = 100°C Human body temp = 37°C

Kelvin scale Metric scale Units = Kelvins (K)

Absolute Zero = 0K (coldest temp = when molecules stop moving)

Celsius + 273K Conversions °C  K

K  °C Kelvin - 273

= 329K Example: 56°C = ? K

400 – 273 = 127 °C Example 400K ? °C

Changing Temp Increasing  heat ADDED Decreasing  heat being REMOVED

CALORIES unit of heat 1 calorie = 4.184 J
How is heat measured? CALORIES unit of heat 1 calorie = J Amount of heat needed to raise the temp of 1g of water 1°C

1000 calories (1 kilocalorie) = 1 food Calorie

Your body uses the calories in food for heat and energy
Your body uses the calories in food for heat and energy. Some foods contain more calories than others, and therefore provide your body with a concentration of energy. Foods that are high in calories contain large amounts of chemical energy, often more than your body can properly break down and use. What's left over is often stored as fat. That's why people on diets avoid foods that are high in calories.

TOPIC: Heat AIM: What is thermal expansion?

Expansion (increase in size) of a substance caused by heat
Thermal Expansion Expansion (increase in size) of a substance caused by heat Temp increases  molecules move faster & farther apart

Examples: 1. The rising of mercury/ alcohol in a thermometer

2. Hot air balloons rise because heated air expands

When both ball and ring are at room temperature, the ball fits through the ring.
When the ball is heated, it no longer fits due to thermal expansion.

Spaces between the joints allow the metals in the bridge to expand.

Read article on thermometer and absolute zero
Summary: Recap lesson Read article on thermometer and absolute zero Paraphrase partners?

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