PHYSICS BLOG

Temperature and Internal Energy

2008-09-05T03:13:00.000-07:00

-Internal energy is basically the total energy of particles due to interatomic and intermolecular bonds.
-Internal energy comprises of two components-kinetic and potential energy.
-Kinetic component is due to the vibrations of the particles.
-An increase in temp will lead to an increase in the kinetic component.
-Potantial component if internal energy is due to the stretching and compressing of the intermolecular bonds.

MELTING AND SOLIDIFICATION
(Melting)
-Melting is the change of state of a solid when it changes to liquid upon heating.
-For pure substances there is a fixed melting point.
-There is no temp change during melting because the temp is used to overcome the strong intermolecular bonds.
(Solidification)
-Solidification is the reverse process of melting.
-For a pure substance the melting and freezing point is the same.
-Similarly there is no temp change because it is used to from the intermolecular bonds in a solid.

BOILING AND CONDENSATION
(Boiling)
-Boiling is when a liquid is heated and changes to vapor at a fixed temp.
-The fixed temp is called boiling point.

(Condensation)
-The reverse of boiling is called condensation.
-Condensation is when vapor changes to liquid when cooled in the same temp as in boiling.

EVAPORATION
-Evaporation is basically a cooling effect.
-Evaporation is the change of state from liquid to gas.
-Evaporation takes place only at liquid surface.

(Factors affecting the rate of Evaporation)
-Temperature-causes greater number of molecules at the surface layer hence they are energetic enough to escape and thus increase the rate of evaporation.

-Humidity-rate of evaporation decreases with increasing humidity.

-Surface area of the liquid-Rate of evaporation increases when surface area exposed is greater.

-Movement of air-rate of evaporation increases when the surrounding air is moving.

-Pressure-reducing atmospheric pressure it increases evaporation.

-Boiling point of the liquid-Liquids with lower boiling points evaporate faster.

Okay ya'll thats bout it.I hope you guys understand thermal physics now (:
Its rather brief because i don't think you'll will wat it to be too wordy so i summarized and only typed out the main points.Feel free to give your comments (:
Peace out!

Transfer of Thermal Energy.

2008-09-04T04:32:00.000-07:00

-Thermal energy always flows from a region of higher temperature to a region of lower temperature.
-Rmb thermal energy is only transferred when there is a DIFFERENCE in temperature.
-When thermal equilibrium is reached there is no net flow of thermal energy.
-Thermal energy is transferred by any of the three processes-Conduction,Convection and Radiation.

CONDUCTION
-Basically conduction is a process of the transfer of thermal energy through a medium,without the medium moving.
-Liquids and gases are poor conductors of heat compared to solids.

All solids are made up of tiny particles called atoms and molecules.(Metals have free electrons while non meals don't)When thermal energy is supplied to one end,the particles will vibrate causing them to collide with neighboring particles.Thus kinetic energy of the vibrating particles is transferred.

For liquids and gases the process of conduction is inefficient,because of the space between the particles in liquids and gases(far apart)hence collisions between particles are less frequent thus the transfer will be slower.

CONVECTION
-Convection is the transfer of thermal energy by means of currents in a fluid,liquid or gas.

(How does it work?)
-When water is heated,it expands.The expandedwater is less dense than the surrounding water and thus it starts to rise.Then the cooler regions of the water in the upper part will be denser and hence it will sink.The movement of the liquid in due to density will start a convectional current.

-Convection currents occur only in fluids such as liquids and gases but not in solids.

RADIATION
-Radiation is the emission of infrared radiation.
-Radiation,unlike convection and conduction, does not require any medium for energy transfer.
-Dull and black surfaces are better absorbers than white surfaces.
-Factors affecting rate of transfer by radiation -colour,texture,surface temp and surface area.

APPLICATIONS OF THERMAL ENERGY TRANSFER
-cooking utensils
-Table mats
-Wooden ladles
-Sawdust
-woollen clothes.

I think that this is pretty impt and helpful because if we blank out and forget about the above,remembering the applications can help us recall (:

The states of Matter.

2008-09-04T02:48:00.000-07:00

-Generally substances can exist in three states of matter-Solid,liquid and gases.

SOLIDS
-Fixed shape and volume.
-High density.
-Incompressible.
-Hard and rigid.

LIQUIDS
-Fixed volume but doesn't have a fixed shape.
-High density.
-Incompressible.

GAS
-No fixed shape or volume.
-Low density.
-Compressible.

*The above are the properties.To understand why they have diff properties we have to understand the nature of matter in a microscopic level.

THE KINETIC MODEL OF MATTER.
-As we all know,at a microscopic level all matter is made up of atoms and molecules (we've learned this in chem!!).And the atoms and molecules are always in a continuous motion.The assumption of the particles in a continuous motion is known as the kinetic model of matter! (:

-The particles in solids are arranged as closely packed.This results in solids having high densities as,when it is closely packed it has a greater mass hence solids have high density.(mass/volume)

-Also solids have fixed volume and shape as the particles in the solid only vibrate about its position.Also it is held be strong intermolecular bonds.

-Liquids also have high densities because the particles are also arranged closely together.

-The particles in a liquid is free to move but within the vessel thats containing it,that's why liquids have fixed volume but not a fixed shape as it takes the shape of the vessel containing it.

-Gases have low densities as the particles are far apart and also its randomnly arranged.The same logic is applied as for the solids,gases have fewer molecules hence density is low.

-Gases have no fixed volume nor shape because particles have very lil attraction between them and move at high speeds.

BROWNIAN MOTION
-Random or irregular motion of smoke particles in air.
-Occurs only in LIQUIDS.
-At higher temperatures the smoke particles will become more agitated and vigorous.Meaning the air particles have greater speeds at higher temperatures.

And i am done for this chapter.I hope you guys understand it.I don't think this chapter is much of a problem as we have done this in chemistry except for the BROWNIAN MOTION.(I like the word Brownian motion.It has the word BROWN..CHRIS BROWN!!!!haha)(: