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 35 o C to 95 o C? (Remember Q = mcΔT) c water = 4190 J/kg o C A kJ B kJ C kJ D 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 32 o F and boils at 212 o F  Celsius – Water freezes at 0 o C and boils at 100 o C  Kelvin – is based off of Absolute Zero  Absolute Zero  So cold that all particles stop moving!  Total energy of the particles is 0.

Temperature:

A piece of metal is heated to 475 o F, what is this temperature in Celsius? A.887 o C B.246 o C C.519 o C D.-27 o C

The melting point of copper is 1073 o C. 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 25 o C to 80 o C? A.5750 J B J C J D 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 K B.3.0 K C K D..33 K

An iron pot containing 5 kg of water at an initial temperature of 23 o C 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 o C B.26.7 o C C.3.7 o C D.76.5 o C

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 Evaporation Boiling 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 L f (or H f )  Latent Heat of Vaporization  The amount of energy required to change a unit mass from liquid to gas (and vice versa).  Abbreviated L v (or H v ) LvLv LfLf

Phase Changes  Latent Heat  Equation: Q = mL Where: Q = heat added during phase change m = mass of sample L = Latent Heat (of fusion or vaporization)  Examples:

How much heat is required to boil 3.5 kg of water? (L v = 2.26x10 6 J/kg) A.7910 J B J C J D J

An experiment is performed and it is found that it takes 13.0 x 10 6 Joules of energy to melt 4.8 kg of iron. What is the Latent Heat of fusion for Iron? A.2.7 x 10 6 J/kg B.2.7 x 10 3 J/kg C.6.2 x 10 7 J/kg D.6.2 x 10 4 J/kg

Latent Heat of Fusion LfLf