Physics

Thermal properties of matter

2008-09-04T05:36:00.000-07:00

THERMAL PROPERTIES OF MATTER

Internal energy is the total energy of the particles(which is held by intermolecular bonds).It is made up of the kinetic energy component and the potential energy component.The kinetic component is because of the vibration of particles relating to temperature.The potential component is because of the stretching and compressing of intermolecular bonds as particles vibrate.

-melting-
melting occurs at constant temperature for pure substances also known as the MELTING POINT.Thermal energy is needed to break the intermolecular bonds of molecules to allow the solid to melt.Thermal energy is absorbed by the substance.

-solidification and freezing point-
it is the change of a liquid state to a solid state.It will solidify at the same temperature as the melting point.there is no change in temperature during solidifiaction.

-Boiling and Condensation-
Boiling is the change of liquid state into vapour state at a fixed temperature(boiling point).Thermal energy is absorbed.Condensation is the opposite.The change of vapour state to liquid state at the same temperature as in boiling.Thermal energy is given out during condensation.

-evaporation-
It is the change of liquid state to gaseous state.It is similar to boiling but the difference is that evaporation can occur at any temperature.There are some factors that affects the rate of evaporation:
1.Temperature
-raising temperature=increase rate of evaporation
2.Humidity of surrounding air
-The rate of evaporation increases with lower humidity(Pr essence of water vapour in air)
3.surface area of liquid
-more exposed surface area=increase rate of evaporation
(because evaporation occurs at the exposed surface of the liquid only)
4.Movement of air
-surrounding air moving increase rate of evaporation.
5.Pressure
-reducing atmospheric pressure=increase rate of evaporation
6.Boiling point of the liquid
Different liquids have different boiling points.Liquids with lower boiling points will evaporate faster.

We have now come to an end of learning the thermal properties of Matter!!So exhausted already!!:)

Transfer of thermal energy

2008-09-04T02:33:00.000-07:00

Thermal energy can be transferred by:
-conduction
-convection
-radiation

no net flow of thermal energy between 2 objects=thermal equilibrium

Conduction
Thermal energy can move through a substance by conduction.
As a heated substance,the particles within gain more energy and vibrate vigorously.Thus colliding into the other particles causing them to vibrate resulting that the heat is transferred to the neighbouring particles.
The 2 processes of transferring thermal energy from the hot to the cold end which occurs in metals and non metals=
-Atomic vibrations
-molecular vibrations

Convection
It is the transfer of thermal energy by means of current in a LIQUID or GAS only.
it is caused by the density change in the various parts of the liquid.

Radiation
it is the continuous emission of infrared waves which does not require a medium to travel from one point to another.This means that thermal energy transfer by radiation can even work in space, but conduction and convection cannot.
It's absorbed and emitted by all objects and surfaces which cause it to have an increase in temperature and a drop in temperature respectively.
Factors affecting rate of radiation
->surface area
->surface temperature
->colour and texture of surface

COMMON APPLICATIONS

-Convection-
1.electric kettles
2.household hot water system
-Radiation-
1.greenhouse
2.vacuum flasks
-conduction-
1.cooking utensils
2.table mats

wao!!this is the end of Transfer of Thermal energy!!I'm feeling the heat!!haha:)

Kinetic Model of MATTER

2008-09-04T01:08:00.000-07:00

Hey!!We actually learn part of this in chemistry and in lower sec before.All substances exist in 3 states of matter.
SOLID
LIQUID
GAS
Kinetic model of matter
Tiny particles moving in continuous motion

The strength of the intermolecular force increases from gas to solid and thus explains the increase in relative distance between particles from solid to liquid.It is arranged closely together from solid and gradually far apart in gas.

Brownian motion

Brownian motion is the random motion of smoke particles in air which only occurs in fluids.(gas or liquid).

higher temperatures=great amount of thermal energy converted to kinetic energy=greater speeds

Temperatures increases=vigorous and agitated motion of smoke particles.

The cause of Brownian motion is by the BOMBARDMENT of air molecules on smoke particles.

That's about it for unit 7.Hope you learned some stuff from here!!:)

2008-09-03T23:17:00.000-07:00

hey this is my first time blogging:)so exciting!!OK.I'll TRY to summarise chapters 7,8&9 about Thermal physics sweet and short!So be prepared!!Sit and learn tight!!