the rope ladder of a boat hangs over the side of the boat and just touches the water. the ladder...

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 rung

B. 2 rungs

C. 5 rungs

D. 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 kJ

B. 628.5 kJ

C. 995.1 kJ

D. 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 ball

B. The banana

C. Both have the same

D. 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 oC

C. 519 oC

D. -27 oC

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

A. 800 K

B. 1899 K

C. 578 K

D. 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 J

B. 18400 J

C. 12650 J

D. 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 K

B. 3.0 K

C. 16810 K

D. .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 oC

B. 26.7 oC

C. 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. water

B. metal

C. They will have same temperature

D. 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 J

B. .0001264 J

C. .0000001264 J

D. 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/kg

B. 2.7 x 103 J/kg

C. 6.2 x 107 J/kg

D. 6.2 x 104 J/kg

Latent Heat of Fusion

Lf