Last but not least, chpt 9

What is internal energy?


Okay, internal energy is simply Kinetic & potential energy.

=You know how to remember?? haha..

I am a K-Poh (Oh no! Im insulting myself..haha, see, Im sacrificing myself for you!)

Kinetic energy is due the vibration of the particles which closely relates to temperature while Potential energy is due the stretching and compressing of molecular bonds

Hence, an increase of temperature would increse kinetic component







Melt, Melt, Melt !

Melting is basically the change of state from solid to liquid.


Imp**During melting, the temperature remains constant at the melting point where thermal energy is absorbed by the substance

As the solids are in fixed position, therefore, the intermolecules bonds must be broken for molecules to move

FREEZE, FREEZE, FREEZE !










Ok, give me a break! not this freeze...but in terms of states..

DO YOU KNOW ? WORLD ICE HOTEL.. no joke



Everything in the Ice Hotel is created from Mother Nature’s glory, from chairs carved out of snow, right down to drinking glasses made of ice. Go http://www.travelscribes.com/ice_hotel.htm for more details if you are intersted

Ok, thats just the intro of how ice can be so beautiful...

Freezing, is the change of state from liquid to solid, without change in temperature.
WHY ? temperature change occur only when substance is cooled within same state when liquid state(90 to 79 degree celcius)

Freezing point is 0 degree celcius..defintely, the pictures above have lower temperatures then 0 degree celcius.. or the hotel would become a swimming pool in no time! I wonder how cold that place will be..

Conversely, liquid molecules come together to solidify & intermolecules would form.

TRY IT OUT (This experiment was in the TB .. You can see the results straight away !
ok..it seems like Im advertising a slimming pill..diao..)


take note at 1:39 is quite funny !

Boiling


Boiling is the change of state from a liquid into vapour, occuring at constant temperature, boiling point
A


Pic A shows how a normal boiling process.
During this process, the temperature remains constant at its boiling point where thermal energy is absorbed.



B



Thermal energy would be used to seperate the molecules





C

The molecules will start to seperate & move further apart..一刀两断





Condensation & evaporation

this cartoon video is quite interesting.. it educates you about condensation & evaporation.Let this be the intro of C&E.Happy watching!

Condensation

When does it occur?

When vapour changes into liquid at the same constant temperature. During this process, heat would be given out.

Similar to boiling, the temperature remains constant at the condensation point.

Evaporation

• When you simply blow your wet hands, evaporation would had already occur. The unique point of evaporation is that it can take place in any temperature. It would dries up any liquid, take for instance, even a swimming pool. But that may take months and it would be a SLOW PROCESS.[depending the variables that would speed up or slow down the evaporation process(will further elaborate below )]. The temperature may also change due to evaporation .
  
  WHY WOULD WE FEEL COLD ?
  
  
  
  
  
  

Lets take for instance when we just came out of swimming pool feeling very cold..This is a common sceneria that would occur in ou common lifes, but have we ever wondered why isit cold? Is it just solely just the wind blowing against us ? As water evaporates, it takes away thermal energy from our skin. As a result, making us feel cold

From the video which educates you about C & E has already explained how evaporation occur. I will now explain again :D As the liquid surface, the ether molecules(more energetic) would overcome the downward attractive force of other ether molecules & escape to the atmosphere.

Evaporation is applied in our common lives. For e.g,

1. the fridge that we use,
2. to dry our wet clothes,
3. to keep a person with high fever's temperature down

VIARABLES THAT AFFECT RATE OF EVAPORATION

Temperature- The higher the temperature of liquid, the increase rate of evaporation

Humidity in surrounding air- Rate of evaporation increase with decreasing humid.

Surface area-The higher the surface area, the faster the rate of evaporation.

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

Pressure- Reducing atmospheric pressureincreases rate of evaporation.

Boiling point of liquid- Liquids with lower boiling point will increase the rate of evaporation

hope you learn something from my blog ;D thanks for reading!

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with my lovely pink