the world of physics

2008-09-05T01:47:00.000-07:00

Internal energy = made up of kinetic energy and potential energy!

Internal energy is defined as the energy associated with the random, disordered motion of molecules

^ temerature = ^ kinetic component of internal energy.

kinetic energy

Vibration of particles/ movement of particles

^ temperature = more vigorous the vibration of particles.

Potential energy

stretching and compressing of intermolecular bonds as particles vibrate.

amount of potential energy stored in the bonds depends on the force between both of them and their distance.

Melting and sodification

solidification and melting are two opposite methods!

solidification:

reverse process of melting!
changing a liquid to solid WITHOUT CHANGE IN TEMPERATURE

temperature remains at constant at freezing point. -thermal energy is released-

Melting:

change of solid to liquid WITHOUT CHANGE IN TEMPERATURE
temperature remains constant at melting point -thermal energy is absorbed-

Boiling and Condensation

Boiling and condensation are two opposite methods!

Boiling:

A PURE liquid is heated and changes vapour at a constant temperature.
during boiling, temperature is constant at its boiling point.
Thermal energy is absorbed by the substance.

Simulations of boiling water

CONDENSATION:

change of state from vapour to liquid when substance is cooled at a constant temperature
during condensation, the temperature remains constant at the condensation point.
thermal energy is released.

Condensation occuring on the glass cup!

EVAPORATION: a cooling process!

due to MOLECULES at the surface with energy greater than the average kinetic energy escaping from the remaining liquid.

Boiling VS Evaporation

Boiling

occurs at fixed temperatures.
Quick process
Takes place throughout the liquid.
Bubbles are formed in the liquid.
Temperature remains constant
Thermal energy supplied by energy source

Evaporation

Occurs at any temperature.
Slow process
Takes place only at the liquid surface
No bubbles are formed in the liquid.
Temperature may change.
Thermal energy supplied by surroundings

Factors affecting rate of evaporation:

Temperature
Humidity of surrounding air
Surface area of the liquid
Movement of air
Pressure
Boiling point of the liquid

Check the video out! =)

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2008-09-03T02:49:00.000-07:00

Fill Three buckets with water. (cold, hot, room temperature respectively)

dip one hand into the cold bucket and the other hand into the hot bucket. obviously one side will feel cool while the other hot.

NOW remove both hands and place them in to the basin filled with water at room temperature.
...
...
...
...
what do you feel?
well the correct "observation" would be you'll feel neither cold nor hot!

What's the logic? welcome to chapter 8~

Chapter 8: transfer of thermal energy

LOGIC:

the feeling of hot/cold proves that thermal energy is transferred only when there is a difference in temperature.
Thermal energy always flow from a region of higher temperature to a region of lower temperature.

One of your hand gains Thermal energy from the hot water while the other loses thermal energy to the cold water. leaving one hand feeling hot and the other cool.
With both hands in the basin of water at room temperature, the temperature of the water is equivalent to the temperature of your hands.

thus, your hands neither feels hot nor cold.

THERMAL EQUILIBRIUM occurs! =)

Thus the LOGIC is shown! =)

Thermal energy may be transferred by any of the three means:

Conduction
Radiation
Convection

CONDUCTION: The process of thermal energy transfer without any flow of the material medium.

when one end of a metal rod is litted with a flame, the other end will becom hot after awhile.
the metalic electrons in the medium moves from the hot end to the cold end.
Once in contact with thermal energy, the particles pass on the kinetic energy by vibration.

* Link back to previous chpt: ^ temperature = more vigorous particles
~ occurs in liquid and gas.

CONVECTION:Transfer of thermal energy by means of currents in a fluid (liguid/gas)

convection only occurs in fluids and not in solid
Movement of air and water particles from a higher region to a lower region.

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RADIATION: the continual emission of infrared waves from the surface of all bodies,transmitted without the aid of a medium.

- Radiation CAN take place through VACUMM
e.g) thermal energy that reaches the earth from the sun is through the process of radiation as there is vacumm between the sun and the earth.

-everything emits off some radiant heat. the hotter the object, the greater amount of radiant heat emitted.

infrarred radiation absorbed by all objects/surfaces = ^ TEMPERATURE.

infrarred radiation emitted by all objects/surfaces = Fall in TEMPERATURE

In general, a good emitter of radiant heat = a good absorber of radiant heat. (vice-versa)

SOME FACTORS that affect the infarred solutions are:

colour and texture of surface. (darker colours/dull absorb more heat than light and shiny colours)
Surface temperatures. ^ temperature of the object to the surrounding temperature = ^rate of infarred radiaton
Surface area. (larger surface area = ^ emition of infrarred radiation at a higher rate)
- A common application for radiation is THE GREENHOUSE

APPLICATIONS OF THERMAL ENERGY:

GOOD CONDUCTORS OF HEAT:

Bad conductors of heat:

And with that, We come to the end of this very very very very very VERY VERY long topic. phew finally.... :D:D
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2008-09-02T23:55:00.000-07:00

Welcome to a blog specially for physics! (chapter 7,8,9)

Well go ahead and read up!

Chapter 7: states of matter and Thermal energy
There are 4 states of matter: Solid, Liquid, Gas and Plasma

The more commnly known states are: Solid, Liquid and Gas.

Check out the table below!

I drew it myself!=) though its a little blur... which i have no idea why... hmm...

The picture below shows the strength in INTERMOLECULAR FORCE

*also drew it myself! :P

Brownian motion.

Random/irregular motion of smoke particles in air.
Occurs ONLY in fluids

The Brownian motion of smoke particles will be more agitated and active at higher temperatures as air molecules have greater speeds at high temperatures!
So that means its;

HIGH TEMPERATURE = HIGH THERMAL ENERGY convertered to GREATER KINETIC ENERGY OF AIR MOLECULES.

thus, Air molecules WILL move faster! :)

THINGS TO TAKE NOTE OF:

DO NOT confuse the NATURE OF BROWNIAN MOTION with the CAUSE OF BROWNIAN MOTION.

The two are different! If you get it wrong then tsk tsk tsk too bad for you. =(

NATURE OF BROWNIAN MOTION: random/irregular motion of tiny particles.

CAUSE OF BROWNIAN MOTION: the motion of fast moving air molecules that bombared the tiny particles!

It's actually quite interesting. The brownian motion that is. You may want to check out these links:

Haha hope it helps!

well actually, I take it that most of us already know about the three sates of matter (solid,liquid,gas) its getting boring..We should study on PLASMA! cool! haha! :P

PLASMA really seems more interesting! its to do with the universe and all... DID you know!

The MAjority of matter in the universe is PLASMA!!!! for example, the stars are made from PLASMA! And majority of matter on earth is solid,liquid and gas! either way, they're both important though I still think that PLASMA would be so much more interesting!

well, that's all for now folks! till the next time! ;)