Just found a funny video about physics! haha~ anyway...this blog is dead...no one will see this bah~? LOL!!! This is about magnetic... Hope U?? will enjoy!! :)
< 11:27 PM >
Chapter 9: Thermal properties of matter
- Wednesday, September 3, 2008 -
Chapter 9: Thermal properties of matter
- Internal energy is made up of kinetic energy and potential energy. - An increase in temperature leads to an increase in the kinetic component of the internal energy.
Melting and Solidification - Melting is the change of state from solid to liquid, without a change in temperature. - Thermal energy helps to break the intermolecular bonds between the molecules of the solid. After it is broken, the molecules move out of the positions, and so the solid has melted. - Solidification is the change of the state from liquid to solid, without a change in temperature. - As the intermolecular bonds are formed to change it’s state from liquid t solid, thermal energy is released.
Boiling and Condensation - Boiling is the change of state from a liquid to vapour, occurring at a constant temperature called the boiling point - Condensation is the change of state from vapour to liquid at the same constant temperature. - Thermal energy helps to separate the molecules and also to push back on the surrounding atmosphere. When the molecules are far apart, a change of state from liquid to gas has taken place.
Evaporation - It is a cooling process and it also causes cooling. - Thermal energy is required. - Factors affecting the rate of evaporation: 1. Temperature: The higher the temperature, the higher the rate of evaporation. 2. Humidity of the surrounding air: The higher the humidity, the lower the rate of evaporation. 3. Surface area of the liquid: The larger the exposed area, the higher the rate of evaporation. 4. Movement of air: When the surrounding air is moving, the rate of evaporation will increase. 5. Pressure: The lower the atmospheric pressure, the higher the rate of evaporation. 6. Boiling point of the liquid: The lower the boiling point, the higher the rate of evaporation.
< 8:47 AM >
Chapter 8: Transfer of Thermal Energy
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Chapter 8: Transfer of Thermal Energy
- Thermal energy always flow from a region of higher temperature to a region of lower temperature. - Thermal energy is transferred by either one of the three processes: 1. Conduction 2. Convection 3. Radiation
Conduction - A process of thermal energy transfer without any flow of the material medium. - Applications of conduction Uses of good conductors of heat:
Uses of bad conductors of heat (insulators):
Solid: - When thermal energy is supplied to one end of a rod, the particles at the hot end will vibrate vigorously. Particles will collide with the others, making them vibrate too. Therefore, kinetic is being transferred. - When metal is being heated, the free electrons in it gain kinetic energy and therefore move faster.
Liquid and Gas: - As the particles of liquids and gases are spaced further apart than those in solid, therefore collision between them are lesser, especially gases. - The transfer of kinetic energy is slow.
Convection
- Transferring of thermal energy by means of currents in a fluid (liquids or gases) - The expanded water that is caused by heated water at the bottom of the flask is less dense compared to the surrounding water, therefore it starts to rise. - Cooler region of the water at the upper part of the flask sink due to the high density. - Applications of convection
Radiation - The continual emission of infrared waves from the surface of all bodies, transmitted without the aid of a medium. - Applications of radiation
Absorption of infrared radiation - The absorption of radiant heat causes a temperature rise.
Emission of infrared radiation - This emission causes the temperature of the objects themselves to fall.
Factors affecting rate of infrared radiation 1. Colour and texture of the surface: Dull/Black surfaces are better absorbers of infrared radiation. 2. Surface temperature: The higher the temperature of the surface of the object compared to the surrounding, the higher rate of infrared radiation. 3. Surface area: The larger the surface area, the higher the rate of emitting infrared radiation.
< 2:42 AM >
Chapter 7: Kinetic Model of Matter
- Monday, September 1, 2008 -
Chapter 7: Kinetic Model of Matter
- Kinetic model of matter is the assumption of tiny particles known as the atoms or molecules in continuous motion.
Arrangement of particles: - The particles of solid are closely packed, regular pattern, high densities. - The particles of liquid are arranged randomly with the particles slightly further apart compared to the solid, relatively high densities. - The particles of gas are very far apart, randomly arranged, very low densities.
Movement of particles: - The particles of the solidvibrate, held by very strong intermolecular bonds. - The particles of the liquid are free to move with little space, attractive forces between them. - The particles of the gas have the very little attraction, move about at high speeds.
- The higher the temperature, the more vigorous the motion of smoke will become due to the air molecules.
