The rope ladder of a boat hangs over the side of the boat and just touches the water. The ladder rungs are 8 inches apart. How many rungs will be under the water when the tide rises 3.5 feet?

A. 1 rungB. 2 rungsC. 5 rungsD. 0 rungs

How much heat would need to be added to a 2.5 kg sample of water in order to increase the temperature from 35oC to 95oC? (Remember Q = mcΔT) cwater = 4190 J/kgoC

A. 366.6 kJB. 628.5 kJC. 995.1 kJD. 1361.8 kj

Because the rubber ball’s temperature increased faster than the banana dipped in LN2, that means which had a higher specific heat.

A. The rubber ballB. The bananaC. Both have the sameD. Neither are capable for getting heat

Pre-AP Physics Unit 5: Thermodynamics

“Thermodynamics”

Is derived from Greek meaning “movement of heat.”

The First Law of Thermodynamics

Official Definition:When heat flows in or out of a system, the energy it gains or loses is equal to the amount of heat transferred.

Or… Heat = Energy ! Is analogous to the Law of Conservation of Energy We are now dealing with Internal Energy

Temperature: What is it?

How “Hot” or “Cold” a substance is. Temperature represents the average

translational kinetic energy of the individual particles in a system.

The Temperature Scales Fahrenheit – water freezes at 32oF and boils at 212oF Celsius – Water freezes at 0oC and boils

at 100oC Kelvin – is based off of Absolute Zero

Absolute Zero So cold that all particles stop moving! Total energy of the particles is 0.

Temperature: Temperature Conversions

Celsius to Fahrenheit

Fahrenheit to Celsius

Celsius to Kelvin

Examples

A piece of metal is heated to 475 oF, what is this temperature in Celsius?

A. 887 oC B. 246 oCC. 519 oCD. -27 oC

The melting point of copper is 1073 oC. What is this temperature in Kelvin?

A. 800 KB. 1899 KC. 578 KD. 1346 K

Specific Heat Capacity What is it?

The resistance to change in temperature of a substance. The Equation:

Q = mcΔT Examples:

How much heat energy is required in order to raise the temperature of a 0.5 kg iron nail from a temperature of 25oC to 80oC?

A. 5750 JB. 18400 JC. 12650 JD. 24150 J

A 75 kg piece of a concrete sidewalk on a sunny day will gain about 650,000 Joules of heat energy from the sun. By how much will its temperature increase on that day?

A. 25133333 KB. 3.0 KC. 16810 KD. .33 K

An iron pot containing 5 kg of water at an initial temperature of 23oC is placed on a stove. If the stove applies 560,000 Joules of heat energy, what is the final temperature of the water?

A. 49.7 oCB. 26.7 oCC. 3.7 oC D. 76.5 oC

A cup of water (c=4190) and a piece of metal (c=350) are both left to sit out on a sunny day. By the end of the day, which will have a greater change in temperature?

A. waterB. metalC. They will have same temperatureD. I don’t know

The Second Law of Thermodynamics Official Definition:

Heat, of itself, never flows from a colder object to a warmer object.

Energy always flows from Hot to Cold This law is also called the Law of Entropy

What is Entropy? The amount of disorder in a system The universe is always moving towards more entropy Examples:

Ice melting Liquid water evaporating

It takes Work (energy) to decrease Entropy

Types of Heat Transfer Conduction

Heat transfer between materials that are in direct contact with each other.

Convection Transfer in a fluid by movement of the substance itself.

Radiation Energy transmitted by electromagnetic waves.

Phase Changes The States of Matter:

Phase Changes Types of Phase Changes:

Melting Evaporation Condensation Boiling Sublimation

Melting

Condensation

EvaporationBoiling

Sublimation

Phase Changes How do you change the melting point or boiling point of

a substance? Add a solute Change the pressure

Phase Changes Energy During Phase Changes

What happens to the temperature of water as heat is added?

It Increases. What happens to the temperature during a phase change?

It remains constant.

Phase Changes Latent Heat

Latent Heat of Fusion The amount of energy required to change a unit mass of any

substance from a solid to a liquid (and vice versa). Abbreviated Lf (or Hf)

Latent Heat of Vaporization The amount of energy required to change a unit mass from

liquid to gas (and vice versa). Abbreviated Lv (or Hv) Lv

Lf

Phase Changes Latent Heat

Equation:Q = mL

Where:Q = heat added during phase changem = mass of sampleL = Latent Heat (of fusion or vaporization)

Examples:

How much heat is required to boil 3.5 kg of water? (Lv = 2.26x106 J/kg)

A. 7910 JB. .0001264 JC. .0000001264 JD. 7910000J

An experiment is performed and it is found that it takes 13.0 x 106 Joules of energy to melt 4.8 kg of iron. What is the Latent Heat of fusion for Iron?

A. 2.7 x 106 J/kgB. 2.7 x 103 J/kgC. 6.2 x 107 J/kgD. 6.2 x 104 J/kg

Latent Heat of Fusion

Lf