# Heat

What is Heat?

Heat is a form of energy.

The Heat of a body is the sum of all the kinetic energy of all the particles in a body.

if the particles have energy, the body has heat !

kinetic energy is the energy of movement

In physics, heat is measured in Joules, after James Joule,

often you may see, kJ, this is simply a kilo Joule, 1000 Joules

remember the particle model of the 3 states of matter,

what happens when you add energy to these particles ??

OP22 understand that heat is a form of energy and that it can be converted into other forms of energy

Heat Energy

OP23 investigate and describe the expansion of solids, liquids and gases when heated, and contraction when cooled

Title

## OP24 demonstrate the expansion of water on freezing

Apparatus

Plastic bottle complete with lid or

Glass Bottle/ Jar with lid

Plastic bag.

Method

1. Fill the bottle to the brim with cold water
2. Measure the volume of water that the bottle holds
3. Refill the bottle to the brim.
4. Screw on the cap tightly.
5. Place the bottle in the plastic bag, tie the top
6. Place bag in freezer

Safety

Tell people that may use the freezer what you are doing and why

Results

Volume 1 84 + 91 + 88 + 89 + 89 + 81

The Volume of the bottle before = 560 ml

The Volume of the bottle after = ml

What did you see?

Maths

Percentage increase in volume

Conclusions

What happens ?

The water freezes and turns into Ice. The Ice takes up more space than water. Water expands when it freezes.

as water freezes it expands, thus it becomes less dense, the ice floats to the top. This means the surface of the pond is frozen, but under is liquid, so the creatures in the pond can stay alive.

## measure the temperature of various solids and liquids at, above and below room temperature; determine the melting point of ice and the boiling point of water

Temperature is a measure of hotness.

We measure Temperature in oC (degrees Celcius)

We measure Temperature using a Thermometer

Anders Celcius in 1742. However Anders made the freezing point of water 100 oC and the boiling point of water at 0 oC. It took the father of taxidermy Carl Linnaeus (a fellow Swedish scientist) to reverse the scale, he took this decision to make the measurements easier to make.

We measured and found the

Melting point of Ice = oC

Boiling Point of Water = oC

Room Temperature = oC

Body Temperature = oC

Temperature of Freshly Drawn water = oC

Using an Infra Red Thermometer

A Candle burns @ 650 oC Matches burn @ 600 oC A Bunsen Burner burns @ 1450 oC

more interesting temperatures here

http://physics.info/temperature/

A table on temperature

## OP26 investigate the effect of pressure on the boiling point of water

The wine preserver!

Clear glass bottle

Liquids turn to gas on boiling. If there is less gas in the space above the liquid, then the liquid turns to a gas quicker (at a lower temperature).

At a lower Pressure water boils quicker or at a lower temperature

At a ____________ water boils at a higher temperature.

## OP27 explain the difference between heat and temperature

To demonstrate this best carry out the following investigation

Title

Do all substances change their temperature at the same rate??

Apparatus

Safety Concerns

Keep the Hotplate at a low setting

Monitor the temperature of the liquids very often,

Turn off the heater if the temperatures get near 60oC

Do not lift / touch the hot liquids.

Method

1. fill 3 beakers with the same volume of the 3 liquids, allow them all time to get to the room temperature.
2. place the 3 beakers on the hot plate
3. carefully measure the temperature of each of the liquids
4. start the clock
5. turn on the hot plate to a medium setting
6. every minute measure the temperature of the liquids TURN OFF THE HOT PLATE WHEN ANY TEMPERATURE IS >50oC
7. continue to record the temperatures every minute.

Results / Observations

Maths

Conclusions

All the liquids recieved the same amount of heat, but the temperature of the liquids changed by different amounts. This shows us that Heat is different to temperature.

Heat is an energy & Temperature is a measure of 'hotness'

The Law of thermometers

Zeroth law of Thermodynamics

This law states that

if object A is in thermal equilibrium with object B,

and object B is in thermal equilibrium with object C,

then object C is also in thermal equilibrium with object A.

This law allows us to build thermometers. For example the length of a mercury column (object B) may be used as a measure to compare the temperatures of the two other objects.

However if a thermometer is taken out of the substance you are trying to measure then, it begins to adjust to the environmental temperature.

Latent heat causes a change in state but no change in temperature.

## OP28 carry out experiments that involve changes of state from

i. solid to liquid and liquid to solid

ii. liquid to gas and gas to liquid

might help with cooling curve graphs ?

http://www.dartmouth.edu/~chemlab/info/resources/linear/linear.html

More on changes of state

http://id.mind.net/~zona/mstm/physics/mechanics/energy/heatAndTemperature/changesOfPhase/changeOfState.html

A trick to play, the gases that come off a hot candle after it is exitinguished are still flammable, try it in a bell jar with a match above the opening ...wager ?

## OP29 plot a cooling curve and explain the shape of the curve in terms of latent heat

might help with cooling curve graphs ?

http://www.dartmouth.edu/~chemlab/info/resources/linear/linear.html

http://www.practicalphysics.org/go/SubmitWebsiteExperiment_207.html

Heating a solid can cause it to melt and become a liquid at a point called its melting point if it’s pure, allowing it to cool again causes it to become a solid again at the same temperature, this time called it’s freezing point. The freezing point can be determined by a simple laboratory demonstration.

Pour Olcetic Acid into a glass.

Place this glass in the freezer.

Remove from freezer and immediatly place a thermometer in and start recording the temperature and the state of the olcetic acid.

Record temp and state every minute until it returns to room temperature.

plot in a graph

Alternative method

Pour acetamide into a test tube until it half fills it. Set up a bunsen burner under a gauze. Place a beaker of water on the gauze with the test tube in it and heat it until the acetamide has melted completely.

As soon as the acetamide has melted, remove the test tube from the beaker and place it in a boss and clamp stand, with a thermometer completely in the acetamide. Record the temperature every thirty seconds to the nearest degree or half-degree Celsius until it reaches about 65°C.

Plot a graph with temperature on the y-axis and time on the x-axis. The melting point is the y value of the flat region of the graph. During this time, heat is lost by forming bonds rather than its temperature falling.

change of state and latent heat

heat energy and temperature; .

## OP30 understand that all hot bodies radiate heat

understand that all hot objects / things give off heat

All hot objects give off their heat until the temperature of the body & its surroundings are the same !!!

more

OP31 carry out simple experiments to show the transfer of heat energy by conduction, convection and radiation; investigate conduction and convection in water

more

OP32 identify good and bad conductors of heat and compare insulating ability of different materials

## Insulation

Evapouration and condensation

Heat homework crossword is here

http://www.sei.ie/Schools/Secondary_Schools/Subjects/Physics/Unit_6_-_Heat_Transfer/Heat_Crossword/

Data Grapher thanks to Zona

http://id.mind.net/~zona/simpleDataGrapher/simpleDataGrapher.html

The temperature of the surface of the sun is about 6000 °C. Sun spots (dark patches) are areas on the sun’s surface at a lower temperature due to variations in the sun’s magnetic field.