L2 - Changes of State

objectives

How can we get all the Jelly out of the Test tube?

•Substances can change shape when they are heated up, or cooled down…

Key words to use:

Heat energy, particles, faster, bonds, melting, evaporating.

Complete the activity by filling in the particle diagrams and explanations on each of the worksheets below:

Change of state cards.doc

Melting (solid -> liquid) such as ice to water. When a substance melts, the fixed particles become able to move around each other.
Evaporating (liquid -> gas) such as water to water vapour. When a substance evaporates, some particles gain enough energy to move fast enough to escape the other particles and escape.

Condensing (gas -> liquid) such as water vapour to water. When a substance condenses, the high energy particles loose energy, and the force of attraction from the other particles becomes sufficient to keep all the particles together (although they can still flow other each other
Freezing (liquid -> solid) such as water to ice. When a substance freezes the particles go from being able to move around each other, to being fixed in place

Dry ice – Solid carbon dioxide. (-78 degrees celsius)

As we place it on a balance what might we see?

Why?

What is happening to the particles?

As the particles in the solid heat up they vibrate faster. Eventually they have enough energy to break the forces holding them in this fixed pattern.

AND …escape from the lattice, straight into the air.

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