Chemistry

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Chemistry

• Chemistry is the central science that studies
  matter and the changes that it goes through!

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• Matter is ANYTHING that has mass and volume.
• Mass the amount of matter in an object.
• Volume the amount of space an object occupies.

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Matter is EVERYTHING except sound or light (both
forms of energy) as well as ideas, feelings,
thoughts or anything else without mass AND
volume!
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• Classifying matter is the process of grouping
  things according to their common traits or
  properties.
• Example Why would a person group English peas,
  asparagus, and lettuce together?

Common Properties They are all green. They are
all veggies.
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Classifying matter is what chemists do to make
sense of the world!

• Properties describe matter.
• There are two types of properties
• physical and chemical

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Physical Properties do not involve a change in
identity of the substance.

• can be observed with the senses (see or smell or
  feel them)
• can be measured without changing the objects
  identity
• examples density, color, odor, taste, hardness,
  boiling melting freezing points,
  conductivity, etc.

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Chemical Properties are observed when there IS a
change in the identity of a substance!

• describes the ABILITY of one substance to react
  with another and produce something NEW
• Example Iron has the ability to rust when
  oxygen is present.
• describes the ability of a substance to NOT react
• Example Gold is desirable for jewelry making
  because it does not react with oxygen to form
  rust.

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Changes in matter often occur.

• There are two types of changes physical and
  chemical.

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Physical Changes

• Changes what the substance looks like, but DOES
  NOT change the substance itself.
• The original substance is NOT destroyed.
• Ask yourself
• Do I still have what I started with? OR
• Can I get back what I started with?
• If the answer is YES to EITHER question, a
  physical change is involved.

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• examples
• cutting wood
• breaking glass
• boiling water
• freezing water
• dissolving sugar in water (called solubility)

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Chemical changes involve a change in identity of
a substance.

• one substance has reacted with another substance
  to produce a NEW substance
• the new substance has different properties (it
  looks different and reacts differently)

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• examples
• exploding or anything to do with fire
  (flammability or combustion)
• rotting/decomposing
• digesting
• neutralization of stomach acid by pepto-bismol

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Word/Phrase Clues to Chemical Changes

• Reacts with
• Produces
• Forms
• Decomposes
• Neutralizes
• Synthesizes
• Combustion flammability
• Any word/phrase that indicates the formation of a
  new substance is a CHEMICAL CHANGE.

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Evidence that a chemical change has occurred

• Bubbles (gas) formed
• Color change (can be physical so be careful)
• Forms a solid (called a precipitate)
• Temperature change (can be physical so be
  careful)
• Releases odor

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• The state of matter is the form in which the
  matter is naturally found based on temperature
  and pressure.

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Solids

• have definite shape and definite volume
• the particles in it are closely packed together
• particles vibrate
• High intermolecular attraction/forces among the
  particles in the solid (this is why they are
  close together they are attracted to each other)

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Liquids

• takes on shape of container
• form of matter that flows because of less
  intermolecular attraction
• particles are closely packed, but less organized,
  and move around more freely

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Gases

• have NO definite shape or volume
• expand to fill container
• easily compressed
• particles are very far apart and fast moving
• low/weak intermolecular attraction (not attracted
  to each other so far apart)

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Plasma

• Not found naturally on Earth EXCEPT in lightning
  bolts.
• Found elsewhere in the sun and stars.

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What is a state change

• A state change means a substance has changed from
  one state of matter to another.
• Example Water freezing involves a change from
  the liquid state of matter to the solid state of
  matter. We can show this as
• H2O (l) ? H2O (s)

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So . . .

• Are state changes physical or chemical changes?
• PHYSICAL!!
• Why?
• When the water is in liquid form it is H2O
  (water). When it is in the solid form as ice, it
  is STILL H2O (water). The identity of the
  substance did NOT change!
• H2O (l) ? H2O (s)
• ALL STATE CHANGES ARE PHYSICAL!

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Finished! Finally! ?