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Transcript of 7.5 Condensation/Evaporation
So far we have observed melting and freezing with wax and sugar. Both materials melted (solid to liquid) and froze (liquid to solid).
In order to melt a solid material you must add heat!
When a solid melts, the kinetic energy of the particles increases until the particles break out of their positions and start to move around and over one another.
Think About Hot Water
What would happen if I continued to heat this water? What would happen to the particles if the kinetic energy continued to increase?
If water boils and turns into gas, where does it go?
What does water vapor look like?
When water turns into water vapor, a gas, is it still water or is it something else?
How can you tell if water vapor is present?
When energy transfers from the water vapor particles, their kinetic energy decreases. The particles stop flying around as gas and bunch together as liquid.
The process of changing state from gas to liquid is called condensation.
When energy transfers to the particles in liquid water, they gain kinetic energy. When a particle gains enough energy to escape the other particles, it flies off as a water vapor particle.
Changing state from liquid to gas is called evaporation.
Condensation & Evaporation
Review Melting and Freezing
Today You Need:
Experiment Part 2 - Add Salt
1) Add 2, 5-mL spoons of salt into your ice cup.
2) Carefully stir the salt into the ice using the stirring stick.
3) Observe for 3 minutes.
Water condensed on the ice cup. Were did that water come from?
Why did liquid water condense on the bottom of the ice cup?
Phase Change Response
Complete Lab Notebook
Describe in detail what happens at the particle level as the water changed phase. Start with the particles in the hot liquid water, and end up with the particles in the solid ice on the cup.
What is the freezing temperature of this unknown liquid? Explain.