Classification of Matter

1
Classification of Matter

• Mixtures
• Chemical and Physical Properties Changes
• Separation Techniques
• Endothermic Exothermic Energy

2
Pure Substances

• These things have a constant composition
  throughout. A sample can be taken from any part
  of the object and it will always have the
  properties.
• Ex hydrogen gas, water, any element from the
  periodic table

3
Elements

• An element is a substance that cannot be broken
  down into simpler substances.
• An element has a fixed composition because it
  contains only one type of atom.

4
Compounds

• A pure substance composed of two or more elements
  joined in a fixed proportion.
• Compounds can only be broken apart by some
  chemical means. Someone cannot pour two glasses
  of water from the same pitcher of water and have
  hydrogen in one glass and oxygen in the other
  glass.

5
Mixtures

• A mixture is a combination of substances that
  combine and keep their own properties. The
  substances can be taken apart by physical means.
  The properties of mixtures can vary because the
  composition of a mixture is not fixed.

6
Mixtures

• There are two types of mixtures
• Homogeneous
• Heterogeneous

7
Homogeneous Mixtures

• Homo meaning same reminds us that homogeneous
  mixtures are the same elements and compounds
  throughout the mixture. One can take a sample
  from anywhere in the mixture and get the same
  results.
• Ex Salt water (liquid) Brass (Cu and Zn)

8
Heterogeneous Mixtures

• Hetero meaning different reminds us that
  heterogeneous mixtures have different elements
  and compounds scattered throughout the substance.
  When a sample is taken from different locations
  within a mixture different elements and compounds
  can be found.
• Ex pizza , concrete

9
Putting it all Together
Matter Has mass and takes up space
Pure Substance Definite Composition
Mixture Variable Composition
Compound 2 or more kinds of atoms
Element One kind of atom
Homogeneous Evenly mixed
Heterogeneous Unevenly mixed
Return to Home Page
10
Solutions, Suspensions, Colloids

• Solution when substances dissolve and form a
  homogeneous mixture Ex water and salt
• Suspension heterogeneous mixture that separates
  into layers over time Ex sandy water
• Colloids some particles that are intermediate
  in size between the small particles in a solution
  and the larger particles in a suspension dont
  separate into layers. Ex fog

11
Physical Properties

• Properties of a compound or element that can be
  tested or observed without changing the identity
  of the substance.

12
Examples of Physical Properties
Property Example(s)
Color Sulfur is yellow
Density Lead is more dense than aluminum
Melting Point The melting point of water is 0 ºC.
Boiling Point The boiling point of water is 100º C
Hardness Diamond can cut a piece of glass because of its hardness.
Metallic Luster (shininess) Gold is very shiny
Ductility Copper is used in wire because it is easily stretched.
Viscosity Honey is more viscous than water.
Conductivity A metal spoon conducts heat more easily than a wooden spoon
Malleability Aluminum is used for foil because it can be rolled into thin sheets.
13
Physical Changes

• A change in size, shape, or state of matter. The
  changes do not alter the substances in the
  material.
• Ex when you drop a piece of chalk and it breaks,
  you change the size of the chalk but you still
  have chalk.

14
Using Physical Properties Changes

• When a scientist is given a sample of a white
  powder and asked to identify it the physical
  changes and properties will help to do so.
  He/she would not want to alter the powder with
  chemical changes and therefore test for physical
  properties and changes of substances that are
  known to be white powders.
• Ex distinguishing between baby powder, flour,
  and powdered sugar

Return to Home Page
15
Separation Techniques

• When different elements and compounds are mixed
  together, its not always a good thing.
  Scientists want to separate the elements or
  compounds from one another. In order to do so,
  they have to perform certain separation
  techniques based upon chemical and physical
  properties of the substances.

16
Density

• When objects have different densities they can be
  separated layer by layer. Water is more dense
  than oil and it settles on the bottom of the
  container. An oil layer forms on the top of the
  container. Oil can then be suctioned off of the
  layer of water.

 
Oil
Water
17
Particle Size (Filtration)

• Just like playing in the sand at the beach, a
  sifter can be used to separate particles based
  upon their size. The bigger particles remain in
  the sifter while the smaller particles fall
  through the holes.

18
Solubility

• Different compounds are soluble in different
  solutions. Mixing the compounds in the liquid
  will create a solution and allow one compound to
  be rinsed from the unknown. Water is often the
  liquid used for this process.

19
Boiling and Melting Points

• When two liquids are mixed together one way to
  separate them is to either freeze them. If one
  has a higher freezing point than the other, it
  will begin freezing leaving the other liquid
  behind. The same holds true for two solids. If
  one has a lower melting point, it will begin
  melting leaving the other substance as a solid.
  This is known as distillation.

20
Chemical Properties

• A characteristic of a substance that indicates
  if it can undergo a certain chemical change.
• Examples of Chemical Properties
• Flammability a materials ability to burn in
  the presence of oxygen.
• Reactivity how easily a substance combines
  chemically/reacts with another substance.

21
Questions to Check for Chemical Properties

• 1. Does it burn in air?
• 2. Does it decompose when heated?
• 3. What happens when it is placed in acid?
• 4. What other chemicals will it react with?
• 5. What substances are obtained from a reaction?

22
Chemical Changes

• A change of one substance in a material to a
  different substance. A distinct odor is produced
  when these changes occur.
• Ex fireworks exploding, matches burning, metal
  rusting

23
Signs of Chemical Changes

• Production of a gas - The foaming of an antacid
  tablet in a glass of water.
• A Change in color - Rusting iron on a car.
• Formation of a Precipitate adding vinegar to
  milk.

24
Endo- Exothermic Reactions

• When a chemical or physical change occurs there
  is energy present. The energy is either absorbed
  or given off as the change occurs.

25
Endothermic Changes

• Endothermic- heat energy is taken in or absorbed
  during a reaction.
• Ex Photosynthesis - a plants food process
• Energy H2O CO2

Sugar O2
26
Exothermic Changes

• Exothermic- reaction that releases heat
• Ex Metabolism releases energy when food is used
  by living cells

Sugar O2 H2O CO2 Energy
Return to Home Page