Methods of Heat Transfer
What are the three methods of heat transfer?
Conduction, Convection, & Radiation
Define specific heat capacity:
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
Define latent heat:
The heat energy used to change phase
What are the four factors that conduction depends on?
1. Material
2. Temperature difference
3. Thickness of material
4. Surface area
Define heat:
The transfer of thermal energy from a warmer object to a cooler object
Define the following:
Conduction
Convection
Radiation
Conduction - heat transfer through direct contact
Convection - heat transfer through the movement of liquids and gases
Radiation - heat transfer through electromagnetic waves
What is the formula for heat energy?
Q = m x c x ΔT
What is the formula for latent heat?
Q = m x L
What are the two factors that convection depend on?
1. Fluid speed
2. Temperature difference
Heat always frows from what temperatures?
Higher temperature to lower temperature
Which type of method does not require matter?
Radiation
Define each variable of the heat energy formula including the units:
Q = heat energy (J)
m = mass (kg)
c = specific heat capacity (J/kg°C)
ΔT = temperature change (°C)
What are the the two types of latent heat? Include the phase changes
Latent heat of fusion (solid ↔ liquid)
Latent heat of vaporization (liquid ↔ gas)
What are the three factors that radiation depends on?
1. Surface color
2. Surface texture
3. Temperature
What is the unit of heat energy?
Joule (J)
Describe what a convection current is:
When a fluid is heated it becomes less dense and rises, as it begins to cool it becomes more dense and sinks.
How much heat is required to raise the temperature of 5.0kg of water from 40°C to 60°C? (c = 4186 J/kg°C)
418600J
How much energy is released when 2.1kg if steam condenses at 100°C? (L = 2.26 x 10^6 J/kg)
4746000J
Which method of heat transfer can travel through space?
Radiation
What is the difference between temperature and heat?
Temperature is the average kinetic energy, heat is the energy transferred due to a temperature difference
Give an example of the following:
Conduction
Convection
Radiation
Conduction: a metal spoon getting hot in soup, touching a hot pan, touch a lava lamp
Convection: boiling water, warm air rising in a room, the movement of lava in a lava lamp
Radiation: sunlight, x-rays, waves
How much energy is required to convert 0.45kg of ice at -20°C into water at 35°C? (c ice = 2100 J/kg°C) (c water = 4186 J/kg°C) (L = 3.34 x 10^5 J/kg)
235130J
A 4.0 kg sample of water at 100°C is cooled until it becomes ice at 0°C. How much total energy is removed? (L = 2.26 x 10^6 J/kg) (L = 3.34 x 10^5 J/kg)
10376000J
All objects emit what?
Infrared radiation
Temperature