Thursday, September 4, 2008

please kindly

click

on the archives of

september 2008

to view

all

the posts

from

chapter 7 to 9.


THANKS! :)


FINISHED!





after two days of hard work, i have completed this entire blog
thanks to all those who have left their comments and who have viewed my blog.
and of course, thanks to those who have been asking me to ADD OIL

i never knew that bloggin can actually be so educational but yet so tiring
but i enjoyed blogging and learning at the same time


to all readers: thanks for viewing. hope that you learn something after viewing.


special thanks to : http://sg.images.search.yahoo.com/
for the pictures.


special thanks to the physics textbook which provided me with the informations :)


EVAPORATION:






- shows water being evaporated.



-drying of hair



drying of wet clothes



puddles of water



puddles of water


++ FACTORS AFFECTING THE RATE OF EVAPORATION.

1. temperature
>> higher the temperature of the liquid,
faster the rate of evaporation

!! heating a liquid will increase the rate of evaporation

2. humidity of the surrounding air
>> rate of evaporation decreases,
with increasing humidity

!! rate of evaporation increases with lower humidity

3. surface area of the liquid
>> rate of evaporation increases,
when there is more exposed surface area of the liquid

!! larger exposed surface area means more molecules can escape from the liquid

4. movement of air
>> rate os evaporation increases,
when the surrounding air is moving

5. pressure
>> reducing the atmosphere pressure,
increases the rate of evaporation.

6. boiling point of the liquid
>> liquids with lower boiling points will evaporate faster.


how does evaporation occur?

~ molecules of liquid are always moving randomly at different speed
~ thermal energy may be absorbed by the liquid from the surroundings
~ at the liquid suface
>> molecules are more energetic
>> are able to overcome the downard attractive forces of other molecules
>> they escapes into the atmosphere


appilcations of evaporation:

1. cooling effect on skin when applying perfume or when perspiration evaporates
2. wet clothes and puddles on water on pavements dry up after a while
3. sponging a patient with a high fever
4. refrigerators uses priciple of condensation and evaporation in cooling process to keep its contents cold

+ EVAPORATION




+ Boiling and condensation

++ lifting ice with string.

TRY IT OUT AT HOME ON YOUR OWN.

ITS PRETTY EASY!

+ solidification and freezing point













+ Melting and Solidification




~ melting:


- when solid changes to a liquid upon heating.




how does a solid melts?

• for solid to melt, bonds have to be broken
• thermal energy helps in the breaking of intermolecular bonds
• when intermolecular bonds are broken, molecules can move out of fixed positions.

UNIT 9:

- Thermal properties of matter

+ particles in a solid vibrate about fixed positions are held together by strong interatomic or intermolecular bonds.


+ total energy of these particles is called : INTERNAL ENERGY


internal energy comprises two components


----- kinetic energy-----


----- potential energy -----




** kinetic component

- due to vibration of the particles

- related to temperature

- higher temperature = more vigorous the vibrations



~ kinetic enegy is due to their movement instead of vibration


** potential component

- due to the stretching and compressing of intermolecular bonds as the particles vibrate



amount of potential energy stored in the bonds depends on the force between the particles and how far apart the particles are.


!! if the temperature of a substance rises, it is due to an increase in the average kinetic energy of its particles only.








potential energy is stores in the slinky as it is stretched or compressed, much like the interatomic or intermolecular bonds of particles.




a microwave oven raises the internal energy of food by making water molecules in the food vibrate vigorously.


APPLICATIONS OF THERMAL ENERGY TRANSFER




---- common applications of radiation ----

1. vacuum flasks

2. shiny teapots




+++ why shiny teapots and not ordinary teapots?

-- shiny surfaces are bad emitters of radiation
-- shiny teapots can keep tea warm for a longer time
-- shiny containers can keep cold liquids cool for longer time


APPLICATIONS OF THERMAL ENERGY TRANSFER





---- common applications of convection ----

1. refrigerators




2. electric kettles




3. air conditioners




APPLICATIONS OF THERMAL ENERGY TRANSFER:



radiation is different from conduction and convection.

1. colour and texture

- dull, black surfaces are better emitters of infrared radiation.

2. surface temperature

- the higher the temperature of the suface of the object relative to the surrounding temperature, the higher the rate of infrared radiation.

3. surface area

- larger surface area will emit infrared radiation at a higher rate.

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


- convection involves the bulk movements of the fluids


- those fluids carry thermal energy


For solids,
- thermal energy is tranferred from one particle to another through

VIBRATIONS.


- without any bulk movement of the particles themselves








Warm air rises and cool air sinks; a convection current forms in a room resulting from uneven heating and cooling


difference between metal and non-metal.

1. metal contains many free electrons

• they move randomly between the atoms or molecules

2. non- metals do not have free electrons

conduction in liquids and gases:

- particles in liquids and gases are spaced further apart

- collision between particles are less frequent in liquid

- collision between particles are even lesser in gases.

- transfer of kinetic energy in particles is slower

Therefore, air is a poor conductor of heat compared to water.

Therefore, air is a poor conductor of heat compared to most solids.

This experiment demonstrates that water is a poor conductor of heat. The ice at the lower part of the test tube does not melt quickly even when the water boils at the top.

Wednesday, September 3, 2008

Heat can be transferred by one of three processes

Conduction

• heat transferred by particles colliding into one another, such as in a metal; not important in the Sun.

Convection

• heat transferred by the circulation of a fluid (or gas), such as in a heating system at home; important near the surface of the Sun.

Radiation

• heat transferred by the flow of electromagnetic radiation, like heat felt from the campfire; important from the core to the surface of the Sun.

http://spaceplace.nasa.gov/en/kids/st8/thermal_loop/index.shtml#

play this!!


thermal energy is transferred by three processes:




unit 8:

-transfer of THERMAL ENERGY



+ thermal energy always flows from a region of higher temperature to a region of lower temperature.

figure 8.1

this figure shows that the heat flows from a region of higher temperature to a region of lower temperature.

• Have you ever wonder why do you feel the heat of the cup of hot coffee?
• And why will the cup of ice tea heat up in your hands?

-that's because the heat from the coffee is flowing from the cup to your hands and

-the body heat will flow to the cup of ice tea and heat it up.

AMAZING ISN'T IT?

this picture is rather blur.
but it can show that the molecule changes from the solid state to the gas state

when the temperature increases:
-a larger amount of thermal energy is converted to kinetic energy
-molecules to move faster.
- molecules overcomes the force of attraction
-able to move more freely
-molecules are moving faster and more freely
- changes its state from solid to liquid and lastly to gas.


Brownian Motion !!!









- smoke particles move irregularly
- particles being bomnared by air molecules
- particles continually bombared unevenly on different sides
- bombaredment reasults in irregular movement






unit 7:

-kinetic model of matter.







arrangement of particles:
- particles CLOSELY packed together
- particles packed in an ORDERLY manner
- LITTLE space inbetween particles
- particles held together by STRONG forces
- particles vibrates about its FIXED position
- particles has LEAST energy
- HIGH density




arrangement of particles:
- particles CLOSELY packed together
- particles are NOT PACKED in an order
- LITTLE space inbetween particles
- particles held together by STRONG forces
- particles FREE to move
- particles has MODERATE energy
- relatively HIGH density




arrangement of particles:
- particles are FAR apart
- particles are in RANDOM position
- particles move FREELY
- particles held together by WEAK forces
- particles has MOST energy
- very LOW density

THE MAIN PURPOSE

main purpose of this blog:

to revisit chpt 7,8,9

to share with my friends what i've
read about

to share about my responses to those chpt

IN SHORT...
this blog will be all about PHYSICS!

THE OWNER

CLARICE YUNG
REG. 09
FROM CLASS 3B1
FROM MR LIM'S PHYSICS CLASS
hits

FREE SPEECH

Links

3B1
Lee Huang
Chara
Christina
Xinyan
Jolene
Germaine
Isabel
Leah
Ziai
Maureen
Melissa
NeoYun
Wan Leng
EnYin
Sheryl
Stephanie
Valerie
Ying Ching
Qing Hui
Vanessar
Joaquim

The flying memories

September 2008

THANK YOU!

Designer:1 2
Basecode:1 2
Pattern:1
Image Hosting:1
REMEMBER!Please DO NOT rip or remove the credits:D! THANKS!