Topic B - The Particulate Nature of Matter

Density

Mass per unit volume

Differences between solids, liquids and gases in terms of arrangement and energy

Solids:

• Most dense

• Strongest intermolecular bonds

• Least KE and PE

• Vibrate around a fixed point in a fixed arrangement

Liquids:

• Irregular arrangement

• Flow around each other

• Stronger intermolecular bonds than gases

Gases:

• Least dense

• Weakest intermolecular bonds

• Most KE and PE

• Can collide with each other

Temperature

Average random kinetic energy of the particles in a substance.

Heat

Transfer of thermal energy from hot to cold.

Thermal equilibrium

When two bodies in contact reach the same temperature and energy transfers stop.

Internal Energy

The sum of the total random kinetic energy and the total intermolecular potential energy of all the molecules. U = E_K + E_P

SHC

The amount of thermal energy required to raise 1 kg of a substances temperature by 1K.

When calculating the temperature change in mixtures what’s the process?

Equate the two substances

• Energy lost by steel = Energy gained by water

Sub in the values making sure that the temperatures are in different positions (T_f - x and y - T_f)

• (4)(450)(T_f - 85) = (10)(4200)(52-T_f)

Solve

What is the gradient on a Temperature Time graph

P/mc

SLH

Amount of energy required to change the state of 1kg of substance from solid to liquid (fusion) or liquid to gas (vapourisation) without any change in temperature.

SLH Equation

Describe the features of a temperature time graph

• During a change of state the temperature stays constant ( so KE stays constant) and energy goes into increasing PE only ( weakening/forming intermolecular bonds)

• A steeper gradients means a smaller SHC as there will be a greater change in temperature.

• Longer time means that there will be more energy and therefore a bigger SLH

Convection and convection currents

Thermal energy transfer throw fluids.

Convection currents form as the fluids heat and up and rise it cools and loses KE and become more dense and sinks which starts a convection current.

Thermal Radiation

The transfer of energy by electromagnetic waves. It doesn’t require a medium and can travel through a vacuum.

• All objects with a temp above 0K emit thermal radiation. The higher the temperature the higher intensity of radiation.

Conduction

• In a sold if one side has a higher temperature then, the particles on that side are moving faster on average.

• This kinetic energy is transferred to the neighbouring particles through collisions.

• Metals are good conductors as they have free electrons which transfer even more energy.

Rate of thermal energy transfer formula

Which state of matter absorbs the most wavelengths

Solids