Chapter 5: Thermal Energy Flashcards
Thermal energy, Conduction, Convection, Radiation, Internal energy, Heat capacity, Latent heat, Boiling and Evaporation
How is thermal energy transfered?
From a region of high temperature to a region of low temperature
What is thermal equilibrium?
A state where there is no net movement of thermal energy
How can thermal energy be transferred?
Via conduction, convection and radiation
How does conduction transfer heat?
Thhrough a medium without any flow of medium
What states does conduction take place, and in which states is conduction the fastest?
Solids (fastest), Liquids, and Gases (slowest)
Why is heat conducted better in metals?
The presence of free electron diffusion aids in conduction of heat
How is equilibrium reached in conduction?
Molecules with more energy collide into molecules with less energy, transferring kinetic energy until equilibrium is reached
How does density affect conduction rate?
The closer particles are to each other (denser), the faster conduction takes place
How does convection transfer heat?
Usage of convection currents in fluids. When a fluid is heated from below, that fluid will expand become less dense and rise, causing the denser fluid to sink onto the heat source, heating that fluid up
What states of matter does convection take place in?
Liquids and Gases
How does radiation transfer heat?
Transfers energy in the form of electromagnetic waves, without the use of a medium
What can be done to increase rate of absorption of heat via radiation?
Increasing surface area, making the surface dull, rough and black
What can be done to decrease rate of absorption of heat via radiation?
Decreasing surface area, making surface shiny, smooth and silver
How is temperature of surroundings related to rate of radiation?
Te higher the temperature of the object relative to its surroundings, the greater the rate of radiation
What is internal energy?
The total energy of all particles in the substance
What does internal energy consist of?
Kinetic and Potential Energy
Which internal energy increases when temperature increases?
Kinetic energy
What is heat capacity?
The amount of thermal energy required to raise the temperature of a substance by 1 degree Celcius or Kelvin
How is heat capacity calulcated?
Heat Capacity (c) = Amount of Energy in Joules (Q) / Change in Temperature (Delta Q)
What is specific heat capacity?
The amount of thermal energy required to raise the temperature of a substance by 1 degree Celcius or Kelvin per unit mass of substance
How is specific heat capacity calculated?
Specific Heat Capacity (c) = Amount of Energy in Joules (Q) / (mass in kg (m) x Change in temperature (Delta Q))
How can thermal energy supplied to a substance be found using its mass, change in temperature and its specific heat capacity?
Q = m x c x Delta Q
What is Latent Heat?
The amount of energy released or absorbed by a substance during a change of state without a change in temperature
What is the Latent heat of Fusion?
The amount of thermal energy needed / released to change a substance from solid to liquid or vice versa without a change in temperature
What is Latent heat of Vaporisation?
The amount of thermal energy needed / released to change a substance from liquid to gaseous or vice versa without a change in temperature
How can specific latent heat be calculated?
Specific Latent Heat = Latent Heat / mass of substance
What are some differences between boiling and evaporation?
Boiling: At a particular temperature, Temperature remains constant, takes place throughout the liquid, bubbles are formed, fast process, external thermal energy is needed
Evaporation: At any temperature, Temperature may change, takes place on the surface of a liquid, no bubbles are formed, slow process, no external energy is needed
What are some factors that affect evaporation?
Temperature - Directly Related
Humidity - Inversely Related
Surface Area of Liquid - Directly Related
Pressure - Inversely Related
Movement of Air - Directly Related
Boiliing Point of Liquid - Inversely Related
