Category: physics

Nutshell: Evaporation and Air Pressure

20121108-073910.jpg
Air Pressure affects the rate of evaporation. The greater the air pressure, the slower the rate of evaporation.

Air pressure is like a ‘force’ that acts on the surface of a liquid. When the ‘force’ is large, the liquid molecules on the top surface cannot easily escape to form the gaseous state.

Advertisements

Nutshell: Cooling and Heating Graphs

Cooling Graph: A temperature graph showing an increase in temperature over a period of time.
20121106-074345.jpg
– example of a cooling graph –

Heating Graph: A temperature graph showing a decrease in temperature over a period of time.
20121106-112441.jpg
– example of a heating graph –

The segments which show constant temperature means that a change in state is taking place.

The possible state changes in a cooling graph are condensation and freezing.

The possible state changes in a heatin graph are melting and boiling.

No Temperature Change = State Change
You can identify the portions which is undergoing state change by looking at which portion is experiencing no temperature change.

Boiling Point
is the temperature at which a liquid changes into its gaseous state.

Melting point is the temperature at which a solid changes into its liquid state.