Describing Matter Ch. 2, Sections 2-3

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Describing MatterCh. 2, Sections 2-3
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• Ch 2, Section 2 Notes
• Physical Properties
• Each specific substance has its own combination
  of properties that can be used to identify the
  substance.
• A physical property of matter is information that
  can be observed without changing the matters
  identity
• Ex hardness, texture, shape, temperature, odor,
  color, density, mass, magnetism
• Identifying Matter
• Examples of using physical properties Does my
  locker have the capacity to hold all my books and
  my binders? - OR Does this neon green shirt
  actually match the pale pink shoes that I want to
  wear to school?
• Density
• Density the amount of matter within a given
  volume
• A golf ball and a table-tennis ball are similar
  in volume, but the golf ball is more dense since
  it has more mass contained in the amount of space

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• Liquid Layers
• Density can cause liquids to separate within a
  container see Fig.4 pg.46
• Liquids with the least amount of density will
  rise to the top and the most dense liquids will
  sink
• Density of Solids
• Density will change if mass or volume is changed
• If mass and volume both change, will density
  change?
• Waters density 1.0 g/mL Materials with
  greater density will sink in water and those with
  less density will float.
• Solving for Density
• Density Mass
• Volume
• Possible units g/cm3, g/mL, kg/m3, kg/L

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• Using Density to Identify Substances
• Density can be used to help identify a substance
  at certain temperatures and pressures. Ex Table
  1 p.47
• Physical Changes Do Not Form New Substances
• A physical change is a change that alters the
  form or appearance of a material but does not
  convert the material into a new substance (change
  that affects 1 physical properties)
• Ex molding a piece of silver into a different
  shape material is still silver
• Examples of Physical Changes
• Freezing water, chopping wood, tearing paper,
  dissolving sugar
• Matter and Physical Changes
• Physical changes do not change the identity of a
  substance
• Changing shape or state of matter molding clay
  or melting butter substance is the same
• Dropping a glass that shatters into pieces

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• Ch 2, Section 3 Notes
• Chemical Properties
• A chemical property describes matter based on its
  ability to change into a new substance with
  different properties.
• Ex Flammability the ability of a substance to
  burn
• Reactivity the ability of a substance to
  combine with another substance (or break down
  into two or more substances) and form something
  new
• Combustibility the ability to plode
• Comparing Physical and Chemical Properties
• Physical properties observable anytime (dont
  change the substance)
• Chemical properties only observable when
  attempting to change the substance into something
  new, always present

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• Characteristic Properties
• The properties most useful in identifying a
  substance are characteristic properties.
• Combination of physical and chemical properties
• Ex A piece of printer paper
• Color white Mass 2.1 grams
• Texture smooth Flammability yes
• Odor none Reactivity (with lemon
• Shape rectangular juice) yes
• Chemical Changes and New Substances
• A chemical change when one or more substances are
  changed into a new substance with different
  properties.
• Chemical changes are the process!
• New substances are formed
• Ex Wood to ash
• Ex Digesting food
• Ex Alka-seltzer and water to a bitter,
  disgusting drink that helps your tummy

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• What Happens During a Chemical Change?
• Ex baking different ingredients are mixed,
  heat is added, and something new is produced
• Signs of Chemical Changes
• Color change
• Gas production
• Change in temperature
• Precipitate formed (precipitate a solid formed
  from solution)
• Change in overall properties
• Matter and Chemical Changes
• Chemical changes are much more difficult to
  reverse than physical changes.

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• Physical vs. Chemical Changes
• The composition of an object or substance is the
  type and arrangement of matter that makes up the
  substance
• Ex Salt is made up of sodium and chlorine and is
  arranged in a 11 ratio.
• A change in Composition
• Physical changes do not change the composition of
  a substance. Ex Water is made up of hydrogen
  and oxygen and is arranged in a 21 ratio. Water
  stays the same if it is in a liquid, gas, or
  solid state of matter.
• Electrolysis the use of an electric current to
  separate water into hydrogen and oxygen gases
• Reversing Change
• Most physical changes can be easily reversed, but
  chemical changes are very difficult to reverse.
• Ex Play-doh can be molded into shapes and then
  back to its original shape.
• Ex Ashes cannot be made back into wood.

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Density Practice Worksheet

• 1 What is the density of carbon dioxide gas if
  .196 g occupies a volume of 100 mL?
• Step 1 Write the formula.
• Density mass
• volume
• Step 2 Substitute what you know
• Density .196 g
• 100 mL
• Step 3 Solve
• Density .oo196 g/mL