Thursday, September 4, 2008
CAHPTER 9! / 5:27 AM
THERMAL PROPERTIES OF MATTER:)
TEMPERATURE AND
INTERNAL ENERGY:)*thermal energy from the Bunsen flame supplied to the water leads to a gain in the internal energy of the water molecules.
KEY IDEAS:[from the TB.]
-internal energy is made up of kinetic energy and potential energy.
-an increase of energy leads to an increase in the kinetic component of the internal energy.
MELTING.
-when a solid changes to a liquid upon heating,this change of state is called melting.
-the point when melting occurs at a definite temperature,it is called the melting point.
-thermal energy is absorbed by the substance.
SODIFICATION AND FREEZING POINT.
-sodification is the reverse process of melting.
-it changes from a liquid to a solid.
-a pure substance will solidify or freeze at a temperature equal to its melting point.
-thermal energy is released by the substance.
BOILING AND CONDENSATION.
-boiling is a state when pure liquid is heated and it changes to a vapor at a fixed or constant temperature.
-the particular temperature is known as the boiling point.
-reverse of boiling=condensation.
EVAPORATION.
-evaporation can occur at any temperature.
-evaporation causes cooling.
[factors affecting the rate of evaporation;temperature;humidity of the surrounding air;surface area of the liquid; movement of air;pressure;boiling point of the liquid.]
*Evaporation occurs when some liquid becomes a gas at temperatures below the boiling point. Molecules escape the body of the liquid and move freely away, as a gas. This happens because some molecules have high enough energy to escape the surface tension of the liquid. Evaporation results in the liquid becoming cooler. Blowing on the liquid increases the evaporation.
CHAPTER 8! / 2:55 AM
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 any of these three processes:Conduction,Convection and Radiation.
*Transfer of thermal energy takes place when there is a temperature difference.
CONDUCTION.
[this transfer of thermal energy through a medium,without the medium moving is called conduction.]
-conduction is the process of thermal energy transfer without any flow of the material medium.
REMINDER:liquids and gases are poor conductors of heat.
CONVECTION.
-Another process of thermal energy transfer is convection.
-Convection is the transfer of thermal energy by means of currents in a fluid(liquids or gases)
RADIATION.
-Radiation does not require a medium for energy transfer.
-Radiation is the continual emission of infrared waves from the surface of all bodies,transmitted without the aid of medium.
[factors affecting rate of infrared radiation:colour and texture of the surface;surface temperature and surface area.]
common applications of convection:electric kettles;household hot water system;air conditioners and even refrigerators.common applications of radiation:teapots;the greenhouse;vacuum flasks.
CHAPTER 7. / 1:27 AM
KINETIC MODEL OF MATTER-
The Basics:
solid:
*fixed shape and volume.
*normally hard and rigid;a large force is needed to change its shape.
*high density.
*incompressible.
liquid:
*fixed volume but does not have a fixed shape.
*high density
*incompressible.
gas:
*no fixed shape or volume.
*low density.
*compressible.
KEY CONCEPTS:
Particles in continuous motion is known as the kinetic model of matter.
Brownian motion is the random or irregular motion of smoke particles in air or pollen grains in water.when temperature increases,the smoke particles or pollen grains are observed to move faster and more vigorously.
Arrangement and movement of particles-
| State | Solid | Liquid | Gas |
| Arrangement of particles | -Close together | -Close together | -very Far apart |
| Movement of particles | -vibrate about fixed positions. -strong intermolecular bonds. | -free to move about but confined within the vessel. | -move about randomly at high speeds. |
| Diagram |  |  |  |
