Heat Flashcards
What is the kinetic molecular theory?
The theory that describes the motion of molecules or atoms in a substance in terms of kinetic energy. Kinetic energy causes particles to be in a state of constant motion.
Define thermal energy?
The total quantity of kinetic and potential energy possessed by the atoms or molecules of a substance. The amount of thermal energy within an object determines how fast it’s particles move (vibrate) therefore how hot/cold it is.
What does an object do when it absorbs thermal energy?
The object warms up.
What does an object do when it releases thermal energy?
The object cools down.
How can thermal energy be transferred?
Thermal energy can be transferred from warm object to cool but not from cool to warm.
Define temperature
A measure of the average kinetic energy of particles in a substance. It is measured using a mercury or alcohol thermometer.
What are the 3 different temperature scales?
Celsius, Fahrenheit, Kelvin
What is the Celsius scale?
This scale is based on the boiling point and freezing point of water. It freezes at O and boils at 100.
What is the Fahrenheit scale?
This scale is based on the boiling point and freezing point of brine. It freezes at 32 and boils at 212.
What is a melting point?
It is the temperature at which a solid changes to a liquid; equal to freezing point for given substances.
What is a freezing point?
It is the temperature at which a liquid changes to solid; equal to the melting point for a given substance.
What is a boiling point?
It is the temperature at which a liquid changes into a gas; equal to the condensation point for the given substance.
What is a condensation point?
It is the temperature in which a gas changes into a liquid; equal to the boiling point for the given substance.
Define heat
Heat is the transfer of thermal energy from a substance of high temperature to a substance of low temperature.
What are the 3 methods of transferring thermal energy?
Conduction, Convection and Radiation
What is conduction?
Conduction occurs when warmer objects are in physical contact with colder objects. The fast moving particles collide with the slow moving particles. (eg. placing a cold spoon in a hot cup of coffee)
What is convection?
Convection is the transfer of thermal energy through a fluid (liquid, gas). This occurs with colder, more dense fluid falls and pushes up warmer, less dense fluid.
What is a convection current?
A convection current occurs when a fluid is continuously heated. (eg. water boiling in a pot)
What is radiation?
Radiation is the movie of thermal energy as electro-magnetic waves. Radiation waves can travel through air, glass or empty space.
Define conductor
A conductor is a material which allows thermal energy to pass through it quickly and easily. (eg. metals)
Define insulator
An insulator is a material that is a poor conductor of thermal energy. (eg. wood)
What is the best insulator?
The best insulator is a vacuum because there are no particles. (eg. thermos bottle)
Define specific heat capacity
Specific heat capacity (c) is the amount of energy required to increase the temperature by 1kg of a substance by 1 degree Celsius.
Define quantity of heat
The total amount of thermal energy transferred from a warmer substance to a colder substance is called the quantity of heat (Q).
If a substance absorbs energy, what is delta T?
Delta T or the change in temperature is positive.
If a substance releases energy, what is delta T?
Delta T or the change in temperature is negative.
What is the principal of thermal energy exchange?
The principal of thermal energy exchange states that when a warmer substance comes into contact with a colder one, thermal energy is transferred from the warmer object to the colder one until all of the thermal energy is evenly distributed (same final temperature for both substances).
Define latent heat
Latent Heat (Q) is the total thermal energy absorbed or released when a substance changes state.
Define latent heat of fusion
Latent Heat of Fusion is the amount of energy that is required to change state from solid into liquid (melt/freeze).
Define latent heat of vaporization
Latent Heat of Vaporization is the amount of energy that is required to change state from liquid into gas (condensing/boiling).
