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.
