Properties of Matter

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Properties of Matter
Physical vs Chemical Chapter 21.4 21.5 P 356-361
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Physical properties

• Physical properties are observations that you
  make without changing the identity of the
  substances that make up the material
• For instance, you can stretch a rubber band or
  bend a piece of wire
• The ability to stretch or bend are physical
  properties
• Some other physical properties are color, shape,
  size, melting point, and boiling point

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Physical Properties

• Appearance
• How would you describe a tennis ball? (shape,
  color, state of matter)
• How would you describe a soft drink? (color,
  state of matter, taste)
• You could also measure its volume and
  temperaturethese are all physical properties

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Physical Properties

• Behavior
• Some physical properties describe the behavior of
  a substance
• For instance, objects containing iron (I.e.
  safety pins) are attracted by a magnet
• Remember that soft drink? If you were to knock it
  over, it would spread onto the table and
  floorthe ability to flow is a physical property
  of liquids

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Physical Change

• If you break a piece of gum, you change some of
  its physical propertiesshape and size
• However, you havent changed the identity of the
  materials that make up the gum
• Each piece still tastes and chews the same

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Physical Propertiesto Separate

• Have you ever licked the icing from the middle of
  a sandwich cookie?
• If so, then youre using physical properties to
  identify the icing and separate it from the rest
  of the cookie
• You can use other physical properties to separate
  such as using a sifter to separate poppy seeds
  from sunflower seeds
• Or sand from iron fillings by using a magnet

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Physical Change

• A physical change is any change in size, shape,
  or state of matter
• These changes might involve energy changes, but
  the kind of substancethe identity of the element
  or compounddoes not change!

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Physical Change

• Remember that when a solid changes into a liquid
  the atoms are not changing.
• Changing State is a physical change!

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Physical Change to Separate

• In some parts of the world, water is very scarce,
  many such areas lie near the sea
• They obtain their drinking water by using the
  physical property of boiling point to separate
  the the salt from the water
• This process is called distillation
• In distillation, you use an apparatus to vaporize
  and condense liquid, leaving the solid material
  behind

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Chemical Properties

• Have you ever seen the warning labels on paint
  thinners and lighter fluids that read FLAMMABLE
• Flammability is a chemical property
• Burning produces new substances during a chemical
  change

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Chemical Properties

• Chemical properties are properties that relate to
  how one substance reacts with others.
• Baking soda has the chemical property that it
  reacts with vinegar to produce carbon dioxide and
  water.
• Copper has the chemical property of reacting with
  carbon dioxide and water to produce a
  greenish-blue solid known as patina.
• Chemical Properties can only be observed by
  changing the substance which turns it into a new
  one.

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Chemical Change

• These two examples involve changing the way the
  atoms in the molecules are arranged.
• When a substance changes by having its atoms
  rearranged it is called a chemical change.
• The baking soda and vinegar underwent a chemical
  change because the atoms that made them up were
  rearranged into carbon dioxide and water.

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How can you tell the difference?

• Sometimes it is difficult to tell the difference
  between a chemical change and a physical change
• Even though when water freezes it looks different
  than liquid water, it is still a physical change.
• However when iron turns to rust it too looks
  physically different but this is a chemical
  change.

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The difference

• A physical change can often be reversed by
  changing the conditions.
• For example to freeze water it has to be cold,
  once frozen the water can be turned back to
  liquid by changing the temperature
• This is not the case for iron turning into rust.
  Once the iron is rusted there is no going back.
• Rust is a new substance with its own properties.

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Other clues

• There are other clues that a chemical change has
  taken place
• You can see a flame
• A gas is produced
• There is a change of color
• A precipitate is formed
• A precipitate is when two liquids are mixed and
  form a solid!
• There is a change in odor

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What is a Precipitate?

• A precipitate is formed when two liquids
  chemically react with each other to form a solid.
• Link

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What kind of change is this?
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In Review

• Physical properties are observed with out
  changing what the substance is.
• Example Water freezes at 0 degrees Celsius but
  frozen water is still water.
• A physical change is often reversible and does
  not change the arrangement of the atoms that
  makes the substance up.
• Example H2O does not change when it freezes,
  melts, of vaporizes. It is still H2O

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In Review

• Chemical Properties can only be observed by
  changing the substance and turning it into a new
  substance
• Example An iron nail and oxygen react to form
  rust which is neither iron or oxygen. It is a
  new substance
• A Chemical Change occurs when a substances atoms
  are rearranged to form a new substance
• Example Copper (a tan colored metal), carbon
  dioxide (a clear, odorless gas), and water (a
  clear liquid) react to form patina, which is a
  greenish solid.

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In Review

• There are 5 signs of a chemical change
• FIRE
• Production of GAS
• COLOR change
• PERCIPITATE
• ODOR