Thermal Physics

Distuingishing features of solids

Definite shape and definite volume, can not flow or be compressed

Distuingishing features of liquids

No definite shape but have definite volume, can flow to take shape of container but can not be compressed

Distuingishing features of gasses

No definite shape or volume, can flow to take shape of caontainer and can be compressed

1) melting, 2) boiling, 3) freezing 4) condensing

Solid arrangement

Regular pattern

Liquid Arrangemen

Irregular arrangement

Gas Arrangemen

Irregular arrangement,

Solid separation

Very closee togethor

Liquid separation

close togethor (touching)

Gas separation

Widely separate

Solid movement

Vibrate arround fixed positions

Liquid movement

Move around each other

Gas movement

Move quickly in all directions

Which 3 things affect the properties of solids liquids and gasses?

Forces and Distance and motion

What happens to the speed of the particles as temperature increases

Increase in kinetic energy so move faster

What is absolute 0

-273 degrees celcius where particles are stationary

What causes an increase in pressure in gasses and why?

Increase in temperature as the particles gain kinetic energy so collide with the walls of the container with more force per unit area

Describe Kinetic Particle Theory/ Brownian Motion

Random collisions between the microscopic particles in a suspension and the particles of the gas or liquid

Evidence for kinetic particle model of matter

Random motion of microscopic particles in a suspension

What causes microscopic particles to move

collisions with fast moving molecules

Microscopic Particles

Something too small to be seen with naked eye but can be seen with light microscope, made of billions of atoms, eg dust pollen

Formula between Kelvin and Celsius

T ( in kelvin) = θ (in celcius) +273

How does increase in temperature effect the pressure with fixed volume

Increases the pressure as the increase in temperature means the particles have more kinetic energy so collide with greater force causing a greater force per unit area

How does a change of volume effect pressure with a constant temperature

If volume increases it causes a decrease in pressure as there is more space in between the particles so there will be less frequent collisions causing less force per unit area.

Equation linking pressure and volume with constant temperature

pV = constant

Graphical display of pV = constant

Why does thermal expansion happen?

The molecules move around faster as they gain kinetic energy This causes them to collide more often and push each other apart

Order how much thermal expansion effects each state of matter

Solids expand the least, then liquid then gas

Why do solids expand less in thermal expansion

The low energy molecules cant overcome the intermolecular forces holding them togethor

Why do liquids expand the amount they do in thermal expansion?

Thry have enough energy to partially overcome the intermolecular forces holding them togethor

Why do gasses expand the most in thermal expansion

The high energy molecules have enough energy to completely break intermolecular forces

Everyday applications of Thermal Expansion

1) Liquid in glass thermometer 2)Temperature activated switches

How do liquid in glass thermometer work?

The thin glass capillery contains a liquid which expands with temperature In one end there is a glass bulb containing a large amount of the liquid which will be expanded into the narrow tube The scales along the side allow the temperature to be measured based on the length of liquid in the tube

How do temperature activated switches work

There is a bimetallic strip which is made of 2 metals which expand at a different rate and bend by a predictable rate and will close the circuit when heated

Effect of thermal expansion

It can cause solid substance to expand if given to much heat so objects built this way have gaps built in to allow expansion to happen without causing damage. ege railway tracks, bridges, roads

Which energy does a rise in temperature in an object increase?

Internal energy

What is an increase in temperature in an object

Increase in the average kinetic energies of all the particles in the object

Define Specific Heat Capacity

Energy required per unit mass per unit temperature increase

Specific heat capacity formula

c = ∆E /(m∆θ), θ is temperature

Plan an experiment investigating specific heat capacity

Place beaker on digital balance and press 0 Add of water and record the mass of water using the digital balance Place immersion heater and thermometer in water Connect circuit with the ammeter in series with the power supply and immersion heater and voltmeter in parallel with the immersion heater Record the initial temperature of the water at 0s Turn on the power supply and start stopwatch Record the voltage from the voltemeter and the current from the ammeter Continue to record temp volt and curretn every 60 sec for 10 min Repeat using solid block of aluminium Calculate specific heat capacity of both

Calculate specific heat capacity using Current Potentail difference and time

c =( IV∆t) /(m∆θ) with I as current and v as p.d and θ as temp

Melting/boiling definition

Energy input without change in temperature

When does water melt and boil

Water boils at 100 and melts at 0 degrees C

Condensation in terms of particles

When a gas cools it loses energy away from the substance and kinetic energy decreases until the boiling point, then energy transferred away reduces potential energy so particles have not enough energy to overcome intermolecular forces and can now only flow over each other

Solidification in terms of particles

When a liquid cools it loses energy away from the substance and kinetic energy decreases until the melting point, then energy transferred away reduces potential energy so particles have not enough energy to overcome intermolecular forces and are now bound to each other nad can onlly vibrate around a fixed point

Evaporation definiton

The escape of more energetic particles away from the surface of a liquid

How does evaporation effeect the liquid left behind

it cools it

Boiling vs Evaporation

Boiling only happens at a fixed temperature (boiling point) while evaporation happens at a range of temperatures below the boiling pointBoiling happens throughout the liquid while evaporation happens at only the surfaceBoiling is a fast process while Evaporation is a slow processIn boiling heat is usually provided by an external source while in evaporation energy is taken from the surroundings

What effects evaporation

Temperature, Surface area and air movement

How does the temperature of a liquid effect its evaporation

Increased temp - increased kinetic energy, molecules at surface more likely to break free of intermolecular forces

How does surface area effect the rate of evaporation

Molecules escape from the surface of a liquid in evaporation so bigger S.A means more area for the liquid to escape from

How does air movement effect the rate of evaporation

Air carries vapour of evaporated liquid away so there is dryer air which accepts water more easily so increasing evaporation

How does being in contact with evaporating liquids affect the temperature of the object and why

Cools the object as the cool liquid absorbs heat from object