Heat and Heat Technology Chapter 10

What is Temperature? Temperature- A measure of the average

kinetic energy of the particles in an object. All particles are in constant motion (even if

they don’t appear to be) The faster the particles are moving, the more

kinetic energy they have. The more kinetic energy they have, the higher

the temperature. Temperature measures the average kinetic

energy of the object because individual particles are moving at different velocities and have different kinetic energies.

Measuring Temperature Using a thermometer-

As a substance’s temperature increases, it’s particles move faster and spread out. There is more space between them, and the substance expands.

Temperature is measured in three ways: Fahrenheit – Used in the US Celsius- Used in rest of the world. The

freezing point and boiling point of water is separated into 100 even intervals

Kelvin- used in science 0 K is the lowest temperature called

Absolute Zero– all molecular motion stops

Measuring Temperature

Temperature Conversion Equations

To convert Use the equation ExampleoC to oF oF = (9/5 x oc) + 32  

See # 1 

oF to oC oC = 5/9 x (oF – 32)  See # 2 

oC to K K = oC + 273   

See # 3

K to oC oC = K – 273   

See # 4

Temperature Conversions Convert 45 oC to oF

Convert 68 oF to oC

Temperature Conversions Convert 45 oC to K

Convert 32 K to oC

Temperature Conversions Convert 35 oC to oF

Convert 75 oF to oC

Convert 68 oF to K

More About Thermal Expansion Expansion joints in highway bridges

Bridges heat up and expand – this can cause the bridge to break so joints are installed.

Hot air balloons When the air inside is heated, it expands

and becomes less dense. The balloon rises.

BNTSG - Heat https://www.youtube.com/watch?v=f1eA

OygDP5s - Clip

https://www.youtube.com/watch?v=svqieBM2ijs

- Full episode

10.2 What is Heat? TRANSFERRED THERMAL ENERGY

Thermal Energy- The energy transferred between objects that are at different temperatures. Energy is always transferred from the

higher temperature to the lower temperature.

Stethoscopes “feel” cold because energy is transferred away from your back to the stethoscope.

Thermal energy is transferredTotal kinetic energy of the particles that makes up the substance

Specific Heat conductors/insulators – A Christmas Story https://www.youtube.com/watch?v=-wj2

Oh50wsA

3 Ways to Transfer Thermal Energy Conduction

Thermal Conduction is the transfer of thermal energy from one substance to another substance through direct contact.

Thermal Conductor- Substances that can conduct thermal energy very well. Ex: Iron

Thermal Insulator- Substances that do not conduct thermal energy well. Ex: Plastic

Ways to Transfer Thermal Energy

Convection The transfer of thermal energy by the movement of a

liquid or a gas. Warm air or liquid rises to the top because it’s less

dense (high energy) At the surface, the warm air/liquid cools, condenses, and sinks back to the bottom.

This cycle is called a convection current

Ways to Transfer Thermal Energy

Radiation The transfer of energy byelectromagnetic

waves such as visible light and infrared waves. This can occur in empty space.

Radiation and the Greenhouse Effect Earth’s atmosphere acts like the

windows of a greenhouse It allows the sun’s visible light to pass

through it. A greenhouse also traps heat, keeping

the inside warm

Transfer of heat song https://www.youtube.com/watch?v=Nbt

VpqYKJWM

Specific Heat Specific Heat-The amount of energy

needed to change the temperature of 1 kg (or g) of the substance by 1°C Metal needs less energy to raise the temperature.

Water needs more energy – high specific heat. Heat can’t be measured directly

We need to use a formula. heat = mass x constant x change in temperature q = mcp∆t

q = mcp(Tfinal- Tinitial)

Specific Heat Calculations

How many joules does it take to heat 20. g of water from 10.0 to 40.0 oC? (Cp (water) = 4.184 J/g oC )

Specific Heat Calculations How much heat is required to heat 75 g

of Iron (Cp = 0.444 J/gCo) from 15.5 to 57.0 oC?

Specific Heat Calculations How many joules does it take to change

the temperature of 15 g of water 25oC? (Cp (water)_ = 4.184 J/g oC )

6.3 Matter and Heat

States of Matter – the physical forms in which a substance can exist. The states of matter depend on the energy of the particles.

Gases = high energy – fast movingLiquids = medium energy – slide past each

otherSolids = low energy – vibrate in place

Changes of State Change of State A change of a

substance from one state of matter to another state of matter. PHYSICAL CHANGE!!!

Include: melting, freezing, vaporization, condensation

An ice cube that melts and then turns to a gas can be graphed on a temperature vs. energy graph.

Heat and Chemical Changes

Calorimeter-a device that measures heat

When one object transfers thermal energy to another object, the energy of the warmer object is absorbed by the other object.

calorie- food is burned, energy released is transferred to the water, temp change of the water can be measured.

1 calorie of food =4.184J of energy.