Discovering Physics.

2008-09-05T18:49:00.014+08:00

Unit 9 - Thermal Properties Of Matter

Objectives:

Understand boiling, evaporation, condensation, melting and solidification.
Understand what internal energy is.
Applications of the different processes.

Internal Energy
Potential energy+Kinetic energy=Internal Energy!

Internal energy of a body is the energy stored in the body.
It is the sum of kinetic energy and potential energy of all particles in the body.
It increases with the temperature of the body and increases when the body changes state from solid to liquid and from liquid to gas.

The stretchable slinky have internal energy stored in it.

In addition, the higher the temperature, the more internal energy it have.

Boiling, Evaporation, Condensation, Melting and Solidification
i spent a long time digging for my last year's revision notes(again created by myself)!
Better appreciate my effort! :D

Below is the heating~~/cooling~~ curve:

Melting
The molecules in a solid gain energy with the increase of surrounding's temperature to break strong intermolecular bonds. Melting occurs at a fixed temperature for every PURE substance, known as melting point. This involves a change of state, from solid to liquid.
Eg. Pure water melts at 0
° C.
Solidification
It is the reverse process of melting and is the same meaning as freezing.
Solidification occurs at a fixed temperature for every PURE substance, known as freezing point. It involves a change of state, from liquid to solid.
Eg. Pure water freezes at 0°C.
Boiling
Molecules gain energy and break loose intermolecular bonds to move freely with the increase of temperature. Boiling occurs at a fixed temperature for every pure substance, known as boiling point.
Eg. Water becomes steam at 100°C.

Here's another Eureka! video on Evaporation & Condensation:
Condensation
It is the reverse process of boiling. It involves a change of state.
Thermal energy is given out during condensation.
VIDEOTIME:
Evaporation
Molecules gain energy from the surroundings to overcome intermolecular forces.
It occurs at any temperature, no definite temperature required.
Similar to boiling, it is the change of state from liquid to gas.
When evaporation occurs, thermal energy is taken away from object, resulting in cooling.
Eg. After a swim, your body feels cold due to evaporation of water.

Factors which affects rate of evaporation:
1. Temperature - High temperatures increase rate of evaporation.
2. Humidity - Rate of evaporation decrease with increasing humidity.
3. Surface Area - Rate of evaporation increase with more exposed surface area.
4. Movement Of Air - Rate of evaporation increase with greater movement of air.
5. Pressure - Reducing atmospheric pressure increases rate of evaporation.
6. Boiling Points - Liquids with lower boiling points evaporates faster.

Applications

Yes! That's the perfume i want! :P
Evaporation occurs when you experience a cooling effect after applying perfume.

Refrigerator makes use of the principles of evaporation and condensation to keep your food cool!

A candle melting. Change of state: Solid wax to Liquid wax

Your clothes can dry because water is evaporated from your wet clothes.

SUMMARY

Last but not least, i found a WATER CYCLE SONG!

2008-09-05T14:47:00.011+08:00

Unit 8 - Transfer Of Thermal Energy

Introduction :D
Thermal Energy always flow from a region of higher temperature to a region of lower temperature. You can relate it to geography too: Hot air rises, Cold air sinks.
The SI Unit of heat energy is joules (J).

Objectives:

Understand Convection, Conduction & Radiation
Learn about applications of Thermal Energy Transfer

Videos speak a thousands words.
Personally, I like Eureka! Videos because they are really educational and engage kids easily.
Their contents are very easy to understand. So i've decided to put up a few here:

Happy Watching! :D

These pictures will help you understand Convection, Conduction & Radiation better.

Conduction - the transfer of heat as a result of the direct contact of rapidly moving atoms through a medium or from one medium to another, without movement of the media.
Metals conduct better than non-metals.

Convection - the transfer of heat by the physical movement of the heated medium itself. Convection occurs in liquids and gases but not in solids.

Radiation - the transfer of heat in the form of waves through space (vacuum).
Dull black surfaces are better than white shining ones at absorbing radiated heat.

Applications
i believe that pictures help us to learn better :D

(explanation in the diagram, written by myself :D)

Frying pans are usually made of shiny stainless steel.
They conduct heat better. :D

Cork mats are known for their insulating properties.

Thermal vacuum flasks are constructed like this to allow better conduction and convection to occur.

This cooker uses convection currents to cook food.

Such induction cookers make use of radiation to cook food.

Handphones, Televisions and microwave ovens require radiation!

2008-09-03T18:36:00.017+08:00

Unit 7
Kinetic Model Of Matter

WHAT YOU'LL LEARN IN THIS UNIT:

Understanding the properties of the 3 states of matter
The effects of temperature on particles (Kinetic theory of matter)
Learn about the Brownian Motion

SOLID
Arrangement - Particles are arranged in a fixed pattern.
Distance Between Particles - Particles are packed closely together.
Force Of Attraction - Very strong forces of attraction between particles.
Motion Of Particles - Particles vibrate about their fixed position.
LIQUID
Arrangement - Particles are packed, but in an inorderly manner, but particles are able to move about.
Distance Between Particles - Particles are less close to one another (as compared to solid).
Force Of Attraction - Force of attraction exist between particles.
Motion Of Particles - Particles interchange their positions.
GAS
Arrangement - Particles are spread widely, free to move anywhere.
Distance Between Particles - Particles are air apart.
Force Of Attraction - Negligible forces of attraction between particles.
Motion Of Particles - Particles move freely and randomly in all directions at high speeds.

Arrangement of the 3 states of Matter:

& The Water Cycle:

Below is comprehensive chart created by myself.
It serves as a summary of the properties of different states of matter.

All matter is made up of tiny little particles called molecules and are always in continuous motion.
This is known as the KINETIC MODEL OF MATTER.

Effects of Heat on Molecular Motion

The higher the temperature, the greater speed the particles move. Vice Versa.

Brownian Motion

Named after Robert Brown. He was the first to observe the random movement of particles, hence the name.
BROWNIAN MOTION is basically the random movement of particles in a random, haphazard and continuous manner, which is also known as the particle theory.
The Brownian Motion explains why perfume smells spreads so quickly :)

Here's a cool software which i found online! Try it out :D
Animated Brownian Motion!
Oh. and:
Brownian Demostration

> Below is a single sample path of a three-dimensional Brownian motion (Wiener process) W_t, as generated by Wolfram Mathematica with a time step of size 0.0001, for times 0 ≤ t ≤ 2.

> Below is Brownian Motion on a Sphere.

BROWNIAN MOTION VIDEO:

2008-09-02T07:50:00.001+08:00

An Introduction to Physics

Physics is a key discipline of Science.
It is the study of the natural world around us, and is divided into 5 main categories:
-General Physics
-Thermal Physics
-Light, Waves & Sound
-Electricity & Magnetism

Thermal Physics will be the general topic of this blog.