How fast do we have to fart in order to achieve lift off?

REVIEW

What is Heat?

It is a form of energy

It is the transfer of energy from one thing to another

Energy flows from HIGH to LOW or HOT to COLD

KINETIC THEORY

• All matter is made up of very small particles (atoms or molecules)

• There are many particles

• The particles are in constant motion

• Collisions are elastic so that no kinetic energy is gained or loss in a collision

• There are forces of attraction and repulsion between particles (intramolecular forces)

• The distance between particles in a gas are larger compared with the size of the particles

Particles in a solid are in constant motion (vibration) around a fixed position

Particles in a liquid have greater amounts of kinetic energy and can move more freely past each other. Bonds are still strong enough to keep the liquid to a fixed volume. It can change shape and flow

Particles in a gas have higher kinetic energy again and are completely separate. Forces between particles are no longer strong enough to hold it to a fixed volume

So as we heat a liquid this is what happens to the movement of the moleculeshttp://www.middleschoolchemistry.com/multimedia/chapter1/lesson2#heating_and_cooling

As energy (heat) is added to an object, the internal energy (kinetic) of that object will increase. This is where Temperature and thermometers come in

So what is Temperature?

Temperature is the measure of the average kinetic energy of the particles in an object

Temperature ScalesThe two you need to know are Celsius and Kelvin.

Celsius is measured in °C and is based on the melting and boiling points of water

Kelvin is measured in K (there is no degrees Kelvin, it is only K) and is the absolute scale. 0K is the theoretical point where particles stop moving

Converting from °C to K

K = C° + 273

Converting from K to °C

C° = K - 273

THERMAL EXPANSION

When an object is heated it will expand. The additional kinetic energy that the particles of an object gain when being heated causes them to vibrate more rapidly and occupy more space.

This is the reason you see the expanding plates on bridges and it is the reason why some rail lines buckle and warp when exposed to extreme temperatures.

It is this phenomenon that allows Thermometers to work.

http://www.middleschoolchemistry.com/multimedia/chapter1/lesson3

Initially the particles in the liquid (in the thermometer) are in constant motion. As heat is added from the outside source, the average kinetic energy of the particles in the thermometer liquid increases.

This leads to an expansion of the liquid. As the liquid expands it flows up the thermometer. It will finally settle when an equilibrium is reached with the substance you are measuring

GASES

An Ideal gas is a model of the behaviour of a gas based on the assumption that there are no forces between the molecules of a gas.

Real gases behave a little differently to “Ideal Gases” but we can use the ideal gas laws to calculate how gases behave under pressure, volume and temperature changes.

P1V1 = P2V2

V1 = V2

T1 T2

P1 = P2

T1 T2

If you increase the volume the pressure decreases (Pressure is inversely proportional to Volume)

If you heat a gas under constant pressure the volume will increase (Volume is directionally proportional to Temperature)

If you have a specific volume of gas and heat it, the pressure will increase. (Pressure is directly proportional to Temperature)

P1V1 = P2V2

T1 T2

You can combine the three Laws into the following

A syringe contains 25cm3 of air, open to the air on a day when the atmospheric pressure is 102kPa. The syringe is then sealed and the plunger pushed until the volume is reduced to 14cm3. What is the new pressure inside the syringe?

P1V1 = P2V2

102 x 25 = P x 14

P = 182 kPa

The air in a pneumatic lift is compressed so that a car can be lifted into place so that it can be worked on. The gas in the lift was at a volume of 50cm3 a pressure of 101.3 kPa and a temperature of 23°C. The gas was compressed to a volume of 20cm3 and the pipe that the gas was in heated up to a temperature of 30°C. What pressure did the gas exert on the pipe?

P1V1 = P2V2 T1 T2

101.3 x 50 = P2 x 20

296 303

17.11148649 = P2 x 20 303

5184.780405 = P2 x 20

259.24 kPa = P2

Heat capacity is the measure of how much energy a substance needs to absorb to change its temperature

Materials with large heat capacities can absorb and store more internal energy, so they take longer to heat up but also longer to cool.

Q = mcΔTQ = Quantity of Heat Energy (J)

m = Mass (kg)

c = Specific Heat Capacity (J kg-1 K-1)

ΔT = Temperature Change (°C)

A kettle is filled up with tap water which is at a temperature of 22°C. If the mass of the water is 1.85kg calculate the energy required to raise its temperature to 100°C

Q = mcΔT

Q = 1.85 x 4180 x (100 – 22)

Q = 603174 J

Q = 603 kJ

A bath is filled with 60L of cool water. The water is at 25°C. The person filling the bath has no hot water but wants to heat the bath to 70°C somehow.

He has a number of objects around the house that he can heat with an outside fire. The objects are as follows

1 x 40kg Aluminium Block

1 x 30kg Iron Anvil

1 x 55kg Copper Pot

What temperature would he need to heat each object to in order to increase the bath temperature by 45°C?

Q = mcΔT

Q = 60 x 4180 x 45

Q = 11286000J

11286kJ of energy required to heat the water

320.625°C

864.83°C

541.42°C

CHANGE OF STATEWhen energy (heat) is applied to an object an increase in the average kinetic energy of the particles occurs. This can be measured as a temperature increase with a thermometer.

At particular temperatures the applied heat causes a change in state. The energy at these stages is absorbed by the particles and used to break up the intermolecular bonds between them. At these stages there is no change in temperature as the applied heat energy is being used to break bonds rather than increase kinetic energy of the molecules

http://www.youtube.com/watch?v=Hsu3JoXN-qU

The energy needed to cause a change of state.

Latent Heat of Fusion = the amount of heat required to change 1kg of a substance from a solid to a liquid (or vice versa)

Latent Heat of Vaporisation = the amount of heat required to change 1kg of a substance from a liquid to a gas (or vice versa)

Q = mL

Q = Quantity of Heat (J)

m = Mass (kg)

L = Specific Latent Heat (J kg-1)

You have a sample of H2O with a mass 23.0 grams at a temperature of -46.0 °C. How many kilojoules of heat energy are necessary to carry out each step? Also, please calculate the total amount of energy needed.

1) Heat the ice to 0.0 °C?

2) Melt the ice?

3) Heat the water from 0.0 °C to 100.0 °C?

4) Boil the water?

5) Heat the steam from 100.0 °C to 109.0 °C?

1. Q = mc∆T = 0.023 x 4180 x 46 = 4422.44J

2. Q = mL = 0.023 x 334000 = 7682J

3. Q = mc∆T = 0.023 x 4180 x 100 = 9614J

4. Q = mL = 0.023 x 2260000 = 51980J

5. Q = mc∆T = 0.023 x 4180 x 9 = 865.26J

TOTAL = 74563.7J

THERMAL EQUILIBRIUM

Heat energy is gained by the colder material equals the heat energy lost by the hotter material.

What is the final temperature of 0.1kg of ice at 0°C added to an insulated container filled with 4.5 kg of water at 20°C?

Heat loss of water = Heat gained by ice + melting of ice

mc∆T = mc∆T + mL

4.5 x 4180 x (20 – T) = 0.1 x 4180 x (T – 0) + 0.1 x 334000

378000 – 18900T = 33400 + 418T

344600 – 18900T = 418T

344600 = 19318T T = 17.84˚C

EvaporationThe fastest, highest energy molecules can break free of the liquid phase. When they do they take the energy with them, hence reducing the overall energy of the liquid.

Reducing the internal energy of a substance will show itself as a reduction in overall temperature.

Evaporation is affected by temperature, humidity and area

VAPOUR PRESSURE & BOILING

A liquid will boil when the vapour pressure within the liquid is equal too or greater than the pressure of the surrounding environment.

Car Air Conditioner

Low Pressure in the pipes causes the refrigerant to evaporate. When a substance evaporates it absorbs heat from its surroundings

This makes the pipes cold. When air is blown over the pipes it becomes cold

When the heat containing gas is compressed under high pressure it reverts back to a liquid. When a substance changes state back to a liquid (condenses) it releases heat into its surroundings

This makes the pipes warm. When air is blown over the pipes it becomes warm

CONTROLLING BODY TEMPERATURE

The human bodies core temperature is generally maintained at or around 37˚C

Sweating is the main way that the body reduces its temperature

In order to warm up the body can reduce blood flow to the skin, lowering the skin temperature. This reduces heat loss from the body’s surface. Goose bumps and pale or blue skin are tell tale signs

Increased metabolic rate is another way to increase body temperature. Shivering is a very effective way to warm your body, provide heat at almost 4 times greater than our normal metabolic rate.

HEAT TRANSFER

CONDUCTIONMain way that thermal energy is transferred in solids. Energy transfer is by molecular collisions or by free electrons

CONVECTIONMain way that thermal energy is transferred in liquids. Warmer liquids (and gases) are less dense so rise. Cooler liquids (and gases) are denser so fall. This cyclic process is known as convection.

RADIATIONTransfer of heat energy from one place to another through electromagnetic waves. INFRARED Radiation.

Black colours absorb radiation at a higher rate but also cool quicker.