Friday, September 5, 2008
Melting
>solid changes to liquid upon heating
>for pure substance,it occurs at a definate temperature known as melting point
>for ice,melting point is 0 degree(constant temp. for ice to melt to become water)
>during changing of states,no change in temp.
Solidification
>reverse process of melting
>changing from liquid to solid
>pure substance solidify at the temperature equal to its melting point
>0 degree is freezing point of water
>during state of change from liquid to solid,no change in temp.
Boiling
>pure liquid heated,changes to vapour at fix temp.(change of state:boiling)
>this particular temp. is known as boiling point
Condensation
>reverse process of boiling
>change of state from vapour to liquid
Evaporation
>change of state from liquid to gas
>can occur at any temp.
>requires thermal energy from surroundings
11:44 PM
Isabel
10:06 PM
Isabel
some comic i found on melting
9:38 PM
Isabel
9:33 PM
Isabel
9:28 PM
Isabel
9:24 PM
Isabel
>melting & boiling graph
9:16 PM
Isabel
Found this interesting :D
9:08 PM
Isabel
>the total energy of the particles in a solid vibrate about fixed positions and are held together by strong intermolecular bonds.
>comprises of kinetic and potential energy
Kinetic energy
>due to vibration of particles
>directly related to temperature
>higher temperature,more vigourous the vibration
Potential energy
>due to stretching & compressing of intermolecular bonds as particles vibrate
>amount of potential energy stored in bonds depends on:
-force between particles
-how far apart the particles are
8:21 PM
Isabel
Diagram on conduction,convection,radiation
7:47 PM
Isabel
3:39 PM
Isabel
3:38 PM
Isabel
Wednesday, September 3, 2008
8:07 PM
Isabel
Firstly,thermal energy always flows from a region of higher temperature to a region of a lower temperature,thus thermal energy can only be transferred when there is a difference in temperature.
Thermal energy is transferred mainly by three processes namely:convection,conduction & radiation.
Convection is the transfer of thermal energy in a gas or liquid (fluid)by movement of currents.
Conduction is the transfer of energy through matter from particle to particle. It is the transfer and distribution of heat energy from atom to atom within a substance.
Radiation: Electromagnetic waves that transport energy directly through space. Sunlight is a form of radiation that is radiated through space to our planet without the aid of a medium. Because there are no solids touching the sun and our planet, conduction is not responsible for bringing heat to Earth. Since there are no fluids in space, convection is not responsible for transferring the heat. Thus, radiation brings heat to our earth.
7:35 PM
Isabel
Brownnian motion can be seen in our daily life too!
7:25 PM
Isabel
This is the brownian motion of smoke particles.The kinetic model of matter tells us that all matter is made up of tiny particles that are in continuous motion.Through brownian motion,we can observe that tiny particles exist,always in continuous motion.This video shows the irregular motion of smoke particles called brownian motion.Smoke particles move irregularly due to the constant bombarding of air molecules unevenly on different sides.
7:20 PM
Isabel
Monday, September 1, 2008
9:51 PM
Isabel
9:40 PM
Isabel
9:20 PM
Isabel
Properties of gas
>no fixed shape or volume
(particles have little attraction between them and move about randomly in high speeds-explains why gases have no fixed volume & shape & highly compressible.)
>Low density
(particles are far apart and randomly arranged.It occupies any available space.-explains why gases have low densities.)
>Compressible
9:08 PM
Isabel
Properties Of Liquid
>Fixed volume, no fixed shape
(Particles are free to move about but confined within the vessel containing it.Have attractive forces between particles-explains why liquids have fixed volumes but take shape of the vessel containing them.)
>High density
(Particles are randomly arranged and slightly further apart-results liquid having relatively high densities.)
>Incompressible
8:56 PM
Isabel
8:09 PM
Isabel
