Changes Of State Powerpoint

Changes of State Grade 9 Chemistry

States of Matter Solid – fixed shape, fixed volume, strong forces between particles This occurs because the particles are in a fixed lattice. So they can not rearrange their shape. The particles in a solid vibrate in position. They are in motion but do not go that fast.

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States of Matter Liquid – variable shape, fixed volume, medium forces between particles When heat is added to a substance, the particles move faster. Eventually they move so fast that they break the lattice bonds and can flow as a liquid. This change of state is called melting.

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States of Matter 3. Gas – variable shape, variable volume, very weak interaction between particles. If you continue to add heat, the particles will move so fast that they evaporate. The molecules then break free of the substance and become a gas. This change of state is called evaporation

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States of Matter There is actually a fourth state of matter that will not be discussed in this course. Plasma – variable shape, variable volume, electrons leave atoms, particles are charged

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Changes of State As heat is added to substances, the substances change state Solid  Liquid (melting) Liquid  Gas (evaporation) Some substances can even go straight from solid to gas Solid  Gas (sublimation) As heat is removed from a substance, Gas  Liquid (condensation) Liquid  Solid (freezing)

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Changes of State How does the temperature versus time graph look? As heat is added, the substance temperature raises. At the melting point, the heat gets used up breaking the bonds. While the heat is being used to break the bonds, the temperature stays constant. The temperature begins to rise again after the change in state. The temperature stop rising again at boiling point The temperature can then rise again.

Temperature

Boiling point

Melting point

Time

Changes of State Temperature 100 C What would the temperature versus time graph look like if the steam (water vapour) started at 1150 C and cooled to – 300 C? 0 C 0

0

Time