Heat

Equation for rate of heat flow

Rate = (kA (T1-T2)) /d

What variables affect the rate of heat transfer?

The conductivity of the material, the temperature difference across the material, the thickness of the material, and the surface area of the material.

Internal/Thermal Energy

The energy formed by the kinetic energy of an object's atoms. It stays within the object.

What determines the rate of heat flow?

The greater the difference in temperatures, the greater the rate of heat flow.

What determines the direction of heat flow?

The heat from the object with the highest temperature gets distributed to the other object.

How does temperature relate to kinetic energy?

The higher the temperature of an object, the more kinetic energy the particles have.

What does the slope look like when two objects are close in temperature?

The lines start closer together on the y-axis and have a shallower slope.

How does a thermometer work?

Mercury expands when heated so when temperatures increase the mercury expands up the tube.

Does material move during heat transfer by conduction?

No, material does not move.

Thermal equilibrium

Objects that are at the same temperature and when touching don't exchange heat.

Heat

A dorm of energy based off how fast atoms are moving in an object.

What is the relationship between the temperature of an object and how much it radiates?

All object with a temperature above absolute 0 produce radiation, but objects with a higher temperature produce more radiation than objects with a cooler temperature.

Explain the movement of fluid during convection. Be sure to include how density is involved.

As fluid is heated, the liquid at the bottom becomes hotter and less dense so it floats to the top where it becomes colder and more dense and moves back to the bottom. The pattern is repeated in a convection current.

How are the methods of heat transfer different from each other?

Each method only works on it's own medium.

How can the rate of heat transfer be controlled?

Heat transfer can be controlled using insulators.

Give examples of heat flowing through natural and forced convection.

If air in a room becomes hot, it will rise to the ceiling where it will cool down and fall back down to the floor. This is natural convection. Forced conduction would be if a fan were blowing on a pot of boiling water.

What is happening at the particle level when energy is being transferred between two objects?

The particles of the warmer object has particles that have more kinetic energy and those particles start to lose their kinetic energy. The particles of the cooler object are moving slowly and they start to gain kinetic energy.

Thermal conductivity

The rate at which heat passes through a material.

Radiation

The transfer of heat in waves through a substance.

Convection

The transfer of heat through liquids or gasses.

Conduction

The transfer of heat through objects that are touching.

K

The variable for Thermal Conductivity which tells you how easily an object allows heat to flow through it. The unit is expressed as Watts per meter.

A

The variable for surface area which affects the rate of heat transfer. The units are cm2 ft2 in2 m2.

T

The variable for temperature which is separated into the temperature of the first object (T1) and the temperature of the second object (T2) in the equation. The unit is usually either Celsius or Fahrenheit.

d

The variable for thickness of the material. The unit is mm.

Temperature

The warmness or coldness of an object.

Why is thermal equilibrium always established when two objects transfer heat?

Thermal equilibrium is established because eventually the particles from the warmer object with more kinetic energy, lose enough energy and the cooler particles with less kinetic energy, gain enough energy that they have the same amount of kinetic energy.

How are the methods of heat transfer similar to each other?

They all transfer heat from hot to cold. In all three methods the heat can transfer enough so that the object reach thermal equilibrium and have the same kinetic energy.

What is similar and different about the three temperature scales?

They are all based off of the freezing and boiling points of water, however they all define them as different numbers. For Fahrenheit, the freezing point is 32 and the boiling point is 212, for Celsius the freezing point is 0 and the boiling point is 100, and for Kelvin the freezing point is 273 and the boiling point is 373.

What does the slope of temperature/time graph look like when two objects are far apart in temperature?

They start farther apart on the y-axis and the slopes are steeper.

Explain what happens to the particles in an object when temperature increases and decreases

When temperature decreases, the particles slow down and don't move as much but when the temperature increase, the particles move faster.

What happens or does not happen at thermal equilibrium?

When two objects are at thermal equilibrium, they are the same temperature and there is no more heat transfer.