IT's PHYSICS

Friday, September 5, 2008

11:46 PM

APPLICATIONS OF CONVECTION and RADIATION

convection first:

1. electric kettles

- hot air rises cold air sinks?same principle here.
- the hot water will go up and the cold water will go down.
- allows the cold water to get boiled at the bottom.
- this is how ur water boils! (:

2. household water system

3. air conditioners
- the hot air will rise (thats why your air-cons are at the top) and get cooled
- the cooled air will then sink down and let the hotter air go up
- kind of like taking turns.
- soon they will all be the desired temperature.

4. refrigerators
- same as air conditioners (:

next radiation:

1. teapots
- shiny = can keep cool or hot
- black CANT keep cool or hot better.

2. the greenhouse
- the plants in the greenhouse emit infrared radiation too.
- this inturn causes the temperature to rise!

LOVE PHYSICS PEOPLE.

2:37 AM

EVAPORATION

liquid ----> gas = evaporation

BEFORE evaporation

AFTER evaporation

occurs at ANY temperature

thermal energy may be absorbed by the liquid from the surroundings

FACTORS.

1. temperature

increase in temperature of liquid = increase in rate of evaporation

2. humidity of surrouding air

increase humidity = decrease in rate of evaporation

3. surface area of the liquid

increase exposed surface area = increase in rate of evaporation

4. movement of air

increase in movement of air = increase in rate of evaporation

5. pressure

increase in pressure = decrease in rate of evaporation

6. boiling point of the liquid

increase in boiling point = decrease in rate of evaporation

LOVE PHYSICS PEOPLE.

1:12 AM

.:MELTING:.

solid ----> liquid = melting

pure substance = definite melting point

to melt,the intermolecular bonds have to break.
thermal energy breaks the bonds and allows the change in state from
solid ---> liquid.

.:SOLIDIFICATION:.

liquid -----> solid = solidification

pure substance = solidifies and freezes at a temperature equal to its melting point

LOVE PHYSICS PEOPLE.

Thursday, September 4, 2008

11:21 PM

GOOD conductors of heat and BAD conductors of heat

the GOOD ones

COOKING UTENSILS
- stainless steel,aluminium
- direct heating involved

SOLDERING
-mainly iron with a bit of copper
-copper is a better conductor than iron

the BAD ones

HANDLES OF APPLIANCES
- prevents us from getting burned!

TABLE MATS
- protects those nice wood table from getting damaged

SAWDUST
- used to readuce ice from melting.WHY?its an insulating property

WOODEN LADLES
- once again, it insulates.

WOOLLEN CLOTHES
- keeps people warm and toasty! (:

LOVE PHYSICS PEOPLE.

8:31 AM

WHAT IS INTERNAL ENERGY?

total energy of intermolecular bonds = internal energy
2 componente basically ONE: kinetic energy TWO: potential energy

KINETIC component

- vibration of the particles related to temperature

- higher the temperature = more vigorous the vibrations

example: microwave

POTENTIAL component

- stretching and compressing of the intermolecular bongs

- amount of potential energy = force between particles and spaces in between the particles

example: slinky

LOVE PHYSICS PEOPLE.

2:04 AM

the THREE states of MATTER

as you can see on the right

1. GAS ---------------------------->
* no fixed shape or volume
* low density
* compressible (can be packed in together)

2. LIQUID ------------------------>
* fixed volume but not fixed shape
* high density
* incompressible (cant be packed in together)

3. SOLID -------------------------->
* fised volume and shape
* normally hard and rigid
* high density
* aslo incompressible (also cant be packed in together)

nothing much for chapter 7 though.
mainly just this,the 3 states of matter.
easy enough?
so far...

LOVE PHYSICS PEOPLE.

2:01 AM

boiling

liquid ----> vapour = boiling
thermal energy pushes the atmosphere back,
thus allowing the molecules to get further apart,
spaced out.

condensation

vapour ---> liquid = condensation
thermal energy is given out during condensation.

LOVE PHYSICS PEOPLE.