12/1/08
Post date: Nov 30, 2008 10:13:44 PM
Bell Activity: With your Oobleck team, prepare a 1-2 minute presentation on your ship and why it is the best design for this mission.
Oobleck presentations
Changes of State
Matter changes from one state to another when we change the temperature (ice --> water at 0 C, water --> water vapor at 100 C)
Since temperature is a measure of average kinetic energy, we see that changes of state are changes of energy
Some changes of state require energy
Energy must be added in order to move from a state with slower moving particles to one with faster moving particles
Melting - Solid to a liquid (ice to water)
Evaporation - liquid to gas (water to water vapor)
Sublimation - solid to gas (snow to water vapor, dry ice to carbon dioxide gas)
Other changes of state release energy
Energy is released in order to move from a state with faster moving particles to one with slower moving particles
Condensation - gas to a liquid (water vapor in the air to dew)
Freezing - liquid to a solid (water to ice)
Deposition - gas to a solid (water vapor to frost)
Temperature is constant during a change of state
When a change of state occurs, all energy added or released is part of the change of state; none of it is part of a change in temperature.
Ex. Boiling water will stay at exactly 100 C no matter how much energy you add to it, and only the water vapor can reach a temperature above 100 C
Ex. Melting ice stays at exactly 0 C until all of the ice has melted into water, then the water's temperature can rise above 0 C.
Conservation of energy
Energy cannot be created
Energy cannot be destroyed
Energy can only change from one form to another, or from one object to another
Conservation of mass
Matter cannot be created or destroyed either
Matter does change into different substances or into different states, but there is always the same total amount of matter in a system