12PHB - Term 2 Flashcards
(24 cards)
Solids definition
Particles are packed tightly in a fixed pattern. Gently vibrating but are held together by a strong force
Liquids definition
Particles are moving and can slide past each other. They are not held together in a fixed pattern. Held together by a weaker force
Gas definition
Particles are spread far apart and move about very quickly forces holding there movement cannot overcome there rapid movements
Easiest way to decide whether conduction is responsible for heat transfer
- Normally in Solids however there are rare instances where is also occurs in liquids and gases
- Objects are touching
- Objects are not moving to cause the transfer (Stationary)
When does Convection occur
Occurs when a fluid is heated causing the movement of groups of atoms or molecules due to variations in density
How does Convection occur
Ek increases -> vibrates more -> Forces weaken -> Moves apart -> Volume increase -> Density Decreases -> Heat rises (vice versa)
Convection
The heat transfer process that occurs because objects are fluid. Their particles are free to move
Radiation
The heat transfers process that occurs without the need for particles/can travel through a vacuum
Specific heat capacity
The specific heat capacity of a substance is the amount of heat energy needed to change the temperature of 1kg of the substance by 1 °C
Latent Heat
A measure of how much heat energy is absorbed or released when 1kg of substance changes state without changing temperature
Conduction
The heat transfer process that occurs because objects are touching.
Degrees Celcius
A temperature scale based around the melting and boiling points of water, Unit = °C
Kelvin
A temperature scale that starts from absolute zero, Unit = K
Absolute Zero
The theoretical temperature at which all particles would stop moving (-273°C)
The average kinetic energy of the particles Equation
Ek = 3/2 kB T
Internal energy meaning
The sum of the total kinetic energy and the total intermolecular potential energy of the particles within the substance
Thermal Equilibrium
When two substances in contact with each other no longer exchange any heat energy and both reach an equal temperature
Why are metals the best conductors
This is because they have a high number of free electrons. Can occur through atomic vibrations and free electrons collisions
Thermal conductivity meaning
The ability of a substance to transfer heat via conduction (Wm-1K-1)
Equation for the rate of heat transfer
∆Q/∆t = kA ∆T/∆x
A perfect black body meaning
An object that absorbs all of the radiation incident on it and does not reflect or transmit any
Intensity-Wavelength graph - Temperature Increases
Peak intensity moves up and to the left. Lower Wavelength but higher intensity
