Changes in state

1
Changes in state

• Lesson 2, Chapter 1, Page E14

2
Essential Questions

• What are the three states of matter?
• How do substances change states?

3
Three states of matter

• Water exists in three states solid, liquid, and
  gas.
• Most matter exists in one or more of these
  states.
• Which state it is in depends on the conditions at
  the time, such as temperature and pressure.
• A solid has a definite shape. For example, when
  you pour ornage juice, a liquid, from a jug into
  a glass, the shape of the juice changes to fit
  the container. The volume doesnt change.

4
Changes in state

• A gas does not have a definite shape or volume.
• For example, if you put air in a tire it take the
  same shape of the tire.

5
Particles of Matter

• You can better understand the differences between
  states of matter if you think of matter as
  particles in motion.
• In a solid the particles are very close together,
  they cant be squeezed any closer together.
• This gives a solid a definite volume and shape.
• In fact, they are packed together so tightly that
  each particle stays in the same place and just
  vibrates.

6
Particles of Matter

• Particles are not packed together as tightly in a
  liquid, so they move more freely than they do in
  a solid.
• This enables a liquid to flow and take a the
  shape of its container.
• The particles in a gas are packed together the
  least. Gas particles move the fastest.
• Like a liquid, a gas flows and takes the shape of
  its container. But the density of particles in a
  gas is so low that an increase in pressure can
  move the particles closer together. When the
  pressure is high enough, a gas becomes a liquid.

7
Changes between States

• You may have seen puddles freeze and turn to ice
  when it gets cold. Freezing changes a substance
  from a liquid to a solid.
• When the sun comes out and warms the ice, it
  melts. Melting is a change in state from a solid
  to a liquid.
• Boiling changes a substance from a liquid to a
  gas. Evaporation occurs when particles escape
  from a non boiling liquid and become a gas.

8
Changes between states

• Condensation changes a substance from a gas to a
  liquid. This is what happens when drops of water
  appear on the outside of glass of cold water on a
  hot day.
• Sublimation is change in state from solid to a
  gas.
• Dry ice, which is solid carbon dioxide, sublimes.
  Without ever melting, in warm air it forms a cold
  gas that looks like smoke.
• Changes in state do not change a substance.

9
Changes Between States

• Water is still water whether it is a solid, a
  liquid, or a gas. Changes in state are also
  reversible.
• Changes in state occur when heat is added or
  removed. When heat is added to a substance, the
  particles gain energy.
• They move faster, and farther apart. When heat is
  removed from a substance, the particles slow down.

10
Melting and Boiling Points

• Freezing refers to the temperature at which water
  freezes. Every substance has its own temperature
  at which it changes from a liquid to a solid.
• This temperature is the substances freezing
  point.
• The temperature at which a substance changes from
  a liquid to a gas is called its boiling point.
  The boiling point of water is 100 degrees C.

11
Summary and Essential Questions

• Three states of matter are solid, liquid, and
  gas. Changes in state are physical changes.
  Particles of matter move faster as head is added
  and slow down as heat is removed. Every substance
  has a melting point, the temperature at which it
  changes from a solid to a liquid. It also has a
  boiling point, the temperature at which it
  changes from a liquid to a gas.
• Now lets answer the essential questions.

12
Assignment

• Answer questions 1-5 on page E19 on a clean
  sheet of paper in complete sentences.
• Using a sheet of construction paper, draw
  something that you learned writing a caption
  telling what your picture shows and tell me about
  the concept that you learned telling me what it
  is you learned.