Unit 2: Matter and Change

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Unit 2 Matter and Change
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OBJECTIVES

• Students will be able to
• define matter
• describe the states of matter (solid, liquid,
  gas)
• identify the characteristics of of a substance,
  element and compound
• distinguish between physical and chemical change
• identify properties of matter (chemical,
  physical, intensive, extensive)
• identify changes in matter that occur (physical
  and chemical change)
• explain the law of conservation of mass

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WHAT IS MATTER?

• Matter is anything that takes up space and has
  mass
• Matter or not?
• gold
• sound
• sunlight
• air
• water
• heat
• thoughts

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MASS WEIGHT

• Mass is the measure of the amount of matter that
  makes up an object
• Weight is a measure of the force of gravity on an
  object
• weight mass x gravity
• weight varies depending on distance from the
  earths surface
• Because the value never changes, scientists use
  mass, not weight to measure matter

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STATES OF MATTER
Shape Takes the shape of container Takes the shape of container Definite shape
Volume Fills volume of container Definite volume Definite Volume
Arrangement of particles Random, far apart Random, close Fixed, close
Attraction between particles Essentially none Strong Very strong
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GAS vs. VAPOR

• Gases and vapors are similar, but terms should
  not be used interchangeably
• Gas refers to a substance that is naturally in
  the gaseous state at room temperature hydrogen
  gas
• Vapor refers to the gaseous state of a substance
  that is a solid or a liquid at room temperature
  water vapor

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THE PHASES OF WATER
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MatterAnything that has mass and takes up space
Pure SubstanceMatter with an unique and
unchanging composition
MixturesA combination of 2 or more pure
substances
physical change
ElementPure substance that cannot be broken into
more simpler substances
CompoundAtoms of two or more elements that are
chemically united in a fixed proportion
HomogeneousMixture/SolutionMixture with a
uniform composition
HeterogeneousMixtureMixture does not appear to
be the same throughout
chemical change
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(PURE) SUBSTANCE

• A substance is a form of matter with an unique
  and unchanging composition (composition doesnt
  change from sample to sample)
• Examples Water, salt
• What about salt water?
• All pure substances are either elements or
  compounds

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ELEMENT

• An element is a substance that cannot be broken
  into more simpler substances
• Examples gold (Au), oxygen (O2)
• To date, there are 118 elements

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COMPOUNDS

• Compounds are substances composed of atoms of two
  or more different elements that are chemically
  united in a fixed proportion
• Water (H2O), sugar (sucrose, C12H22O11), ammonia
  (NH3)
• Compounds can be separated back into its elements
  (by chemical means)
• Electrolysis of water
• 2H2O ? 2H2 O2

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PROPERTIES OF MATTER

• Every pure substance has a unique set of
  properties
• A property is a characteristic that allows us to
  recognize a certain type of matter

Physical properties of water
clear liquid at room temperature
boils at 100oC
freezes at 0oC
density at 4oC is 1.000 g/cm3
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PHYSICAL PROPERTIES

• Physical properties are those properties that can
  be measured without changing the identity of the
  substance
• color, odor, melting point, boiling point,
  density, hardness, taste
• Physical properties are either extensive or
  intensive

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Extensive property Intensive property
A property that depends on the amount of a substance present Example Mass, volume, length value will change when the amount of substance changes 1 mL of water has a mass of 1 g while the mass of 1 L has a mass of 1000 g A property that is independent of the amount of substance present Example Density, boiling point, melting Point value will not change when the amount of substance changes The density of water is always 1.00 g/mL
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CHEMICAL PROPERTIES

• Chemical properties describe the way a substance
  may change or react to form other substances
• Corrosion, flammability
• The inability of a substance to change is also a
  chemical property
• Argon gas is inert
• To observe a chemical property a chemical change
  must occur

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PROPERTIES OF COPPER
Physical properties Chemical properties
reddish brown, shiny Forms a green copper carbonate compound when in contact with moist air
good conductor of heat Forms new substances when combined with nitric sulfuric acid
Density 8.92 g/cm3 Forms deep blue solution when in contact with ammonia
Melting point 1085oC Forms deep blue solution when in contact with ammonia
Boiling Point 2570oC Forms deep blue solution when in contact with ammonia
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CHANGES IN MATTER

• A physical change is a change that alters the
  appearance of the substance drastically but
  leaves its composition unchanged
• bend, grind, split, crush, boil, freeze, melt,
  vaporize

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Chemical Change (Chemical Reaction)

• In a chemical change a substance is transformed
  into a chemically different substance
• When hydrogen burns in air it reacts with oxygen
  to form water
• The new substances formed have different
  compositions and different properties
• Terms Explode, rust, oxidize, corrode, tarnish,
  ferment, burn, rot etc.

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EVIDENCE OF CHEMICAL CHANGE

• Formation of a gas or solid color change energy
  change odor

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PHYSICAL OR CHEMICAL CHANGE?

• Plants use carbon dioxide and water to make
  sugar.
• On a cold day, water vapor in the air forms frost.

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THE LAW OF CONSERVATION OF MASS

• Mass (matter) is neither created nor destroyed
  during a reactionmass is conserved
• Massreactants Massproducts

2HgO ? 2Hg O
216 g ? 200 g 16 g
reactants ? products
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PRACTICE PROBLEM

1. In a complete reaction of 22.99 g of sodium with
   35.45 g of chlorine, what mass of sodium chloride
   is formed?
2. A 12.2-g sample of X reacts with a sample of Y
   to form 78.9 g of XY. What is the mass of Y that
   reacted?