Elements_ compounds _ Mixtures

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Elements, Compounds and Mixtures
Elements, Compounds & Mixtures
 Scientists like to classify things

 One way that scientists classify
  matter is by its composition

 Ultimately, all matter can be
  classified as elements,
  compounds and mixtures
 Why isn’t it a good idea to
 classify matter by its state?

 Because one kind of substance can exist in
 more than one state – such as H2O. And
 matter changes states rather easily.
Why isn’t matter classified
according to its physical
characteristics, such as color?

 Scientists wouldn’t find it very useful to
  group gold, sunflowers, and the sun together.
 Scientists ask themselves these questions:

  Is the matter uniform throughout?
  Can it be separated by physical means?
  Can it be separated by chemical means?
By asking these questions scientists can classify matter
 Elements – simplest form of pure substance. They
  cannot be broken into anything else by physical or
  chemical means.

 Compounds – pure substances that are the unions of
  two or more elements. They can be broken into
  simpler substances by chemical means.

 Mixtures – two or more substances that are not
  chemically combined with each other and can be
  separated by physical means. The substances in a
  mixture retain their individual properties.
   Solutions – a special kind of mixture where one
    substance dissolves in another.
Chapter 4
I. Element:

 Pure substance that cannot be
 separated into a simpler
 substance by physical or
 chemical means
Pure Substance:
 Only 1 type of particle (atom)

 Elements are pure substances

 Compounds may be a pure
 Compounds may NOT be a pure
A. Characteristic Properties

  Every element has a unique set
  of properties

  Properties do NOT depend on
  the amount of material
1. Physical Properties:

 Boiling point
 Melting point
 Density
 Color
 Texture
2. Chemical Properties:

 Reactivity with acid
 Reactivity with other
 Flammability
B. Classification of Elements:
 Classified by their properties
 Identified by their properties
 Arranged in the periodic table in
  a certain area due to their
3 Classes of Elements:

1. Metals
2. Nonmetals
3. Metalloids
1. Metals
  Ex. iron (Fe), nickel (Ni), cobalt (Co)

  ALL metals are:
       Conduct thermal energy
       Conduct electric current
 Not all metals are exactly alike,
 some may be more malleable
 than others, etc
2. Nonmetals
 Share the following characteristics:
       Poor conductors of thermal
        energy and electric current
       Solid nonmetals tend to be
        brittle and unmalleable

 Ex. graphite (carbon) used in
  pencils; neon - gas used in lights
3. Metalloids
 Semi conductors
 Some shiny
 Some dull
 Somewhat malleable and ductile
 Some conduct thermal energy
 and electrical
Section 1 Review Quiz!
1. What is a pure substance?

2. List three properties that can
   be used to classify elements.

3. What are the three classes of elements?

4. What class is said to be “dull”?
   Good conductors of electricity?
II. Compounds:
A. Most elements are not found
   alone in nature, most are
   found in combination with
   other elements
 Compound: a pure substance
 composed of two or more
 elements joined together
   Chemically joined to one
   In order to break apart, the
    substance must react or
    undergo a chemical change
Most substances you are
 familiar with are compounds
Compounds are completely
 different from the elements
 they are composed of
   Ex. NaCl (table salt)
 Na (sodium):
      Soft, silvery white metal
      Reacts violently with H2O (water)

 Cl (chlorine):
       Poisonous greenish/yellow gas

 When Na & Cl are chemically
 combined, they form hard whitish
 crystals that we call table salt – NaCl
 is a completely new substance
B. Elements combine in a definite
   ratio to form a compound:
     Compounds are NOT random
     1 atom of oxygen + 2 atoms of H  H2O
     If another ratio occurs, such as
      2 atoms of H and 2 atoms of O,
      you get a substance known as
      hydrogen peroxide: H2O2
C. Each and every compound has
  a unique set of properties:
  These properties help distinguish
   compounds from other
   compounds and elements
1. Physical properties:
     Boiling point
     Melting point

2. Chemical properties:
    Reaction with acid
    Reaction with light
D. Compounds can be broken down
   into simpler substances:
     Since compounds are chemically
      bonded together, they can only be
      broken apart by chemical changes:
         Burning, electrical currents or
          reacting with other elements or

 Compounds cannot be broken down
 by physical means: grinding, tearing
 or filtering
E. Where are compounds?

 Almost everywhere!

    Water: H2O
    Glucose: C6H12O6
    Vitamin C: C6H8O6
    Carbon dioxide: CO2
Caffeine has a
significant effect
on spiders, which
is reflected in the
construction of
their webs.
Splenda: C12H19Cl3O8
Sweet choices
The Food and Drug Administration (FDA) has approved the following low-calorie sweeteners for
use in a variety of foods. The FDA has established an "acceptable daily intake" (ADI) for each
sweetener. This is the maximum amount considered safe to eat each day during your lifetime.
ADIs are intended to be about 100 times less than the smallest amount that might cause health

                                                    Estimated ADI           OK for
        Artificial sweetener       ADI*
                                                    equivalent**            cooking?
                            50 milligrams
        Aspartame                                   18 to 19 cans of
                            (mg) per                                        No
        (NutraSweet, Equal)                         diet cola
                            kilogram (kg)
        Saccharin (Sweet'N               9 to 12 packets of
                            5 mg per kg                     Yes
        Low, SugarTwin)                  sweetener
                                         30 to 32 cans of
        Acesulfame K
                            15 mg per kg diet lemon-lime    Yes
        (Sunett, Sweet One)
                                         6 cans of diet
        Sucralose (Splenda) 5 mg per kg                     Yes

*FDA-established acceptable daily intake (ADI) limit per kilogram (2.2 pounds) of body weight.
**Product-consumption equivalent for a person weighing 150 pounds (68 kilograms).
***These products usually contain more than one type of sweetener.
Splenda: C12H19Cl3O8
Aspirin: C9H8O4
Ammonia: NH3
Bubble gum: C6H14O6
Borax: Na2B4O5(OH)4
Teflon: -(CF2CF2)-
Ozone: O3
Section 2 Review Quiz!
1. What is a compound?

2. How are compounds and elements different?

3. Name some common compounds.

4. How does a compound differ from the
  elements that make it up?

5. If two compounds contain hydrogen and
  oxygen, are they both water?
III. Mixtures:
 A combination of two or more
 substances that are NOT
 chemically combined

 Ex. pizza, trail mix, tea, blood
A. About Mixtures:
1. Properties:
   Substances in a mixture
    retain their own identity
     Ex. cheese and tomato sauce
      do not react chemically to
      produce a new substance
 Ex. Granite is a mixture. It can
  have different colors. In
  general, it is a combination of:
     Quartz: colorless
     Feldspar: pink
     Mica: mica
2. Some mixtures are not easily
   “seen” because they are well
       Ex. tea, salt water, milk

           vitamin D & calcium
Homogenization of Milk
B. Separation of Mixtures

  Can be separated by physical

  No chemical bonds need to be
Common Techniques:
1. Filtering
2. Distillation: a process that
   separates a mixture based on the
   boiling points of the components
3. Pick
4. Magnet
5. Centrifuge: a machine that
   separates (usually blood) by
   spinning at high rates of speed
   and separates substances by
   their densities

                     white blood cells
                       red blood cells
Sorting it All Out!
 Why can the parts of a mixture be
 more easily separated than the
 parts of a compound?

 Suppose you had a mixture of sand
  and water. What are two ways you
 could separate the mixture?
 Suppose you had a mixture of sand
 and salt. What are three steps you
 would need to take to separate the

 Suppose you had a mixture of
 pepper and iron filings. How could
 you separate that mixture?
 You made some beef soup. You
 want to separate the extra fat
 from the soup before you eat
 it. How could you do that?
C. Mixtures Do NOT have
   a definite ratio:
  Air is a mixture of: oxygen,
   nitrogen, CO2, and H2O
  Some days may be more
   humid than others = more
   water vapor, but still air and
   still a mixture
D. Solutions
   (Homogeneous Mixture):
  A mixture that appears to be a
   single substance but is
   composed of particles of two or
   more substances
  The substances are distributed
   evenly amongst each other
1. Dissolving:
   The process in which particles
    of substances separate and
    spread evenly throughout a
     a. Solute: the substance getting
     b. Solvent: the substance in
        which the solute is dissolved
 Ex. salt water:
       solute: salt
       solvent: water
The solute is soluble
 (able to be dissolved)
An insoluble substance
 does not dissolve and
 therefore does NOT form
 a homogenous mixture
2. States of Solutions:
     Not all solutions are liquids
     Solutions can be solids, liquids,
      and/or gases
     Ex. alloys are solid solutions
          air is a solution: water
          dissolved in gases, and
          gases dissolved in gases
          14 karat gold is a solution!
Particles in a solution are so
 small they do not scatter

E. Calculating the % of Solutions:

 24 karat gold is 100% pure gold
 12 karat gold is 50% gold
 What % of gold is in 14 karat gold?

 Concentration is the measure of
  the amount of solute dissolved in
  a solvent
 % is calculated by placing the
 part over the whole and
 multiplying by 100

 We calculate % when we have
 the same states of matter for
 both the solute and solvent
 If we have two different states
 of matter, such as a solid in a
 liquid, we do not find a %

 The concentration is reported
 out as g/L, g/mL, mg/mL, etc
 Three terms used to describe
 solutions are:
        1. Saturated
        2. Unsaturated
        3. Supersaturated
1. Saturated:
     A solution that contains
      all the solute it can hold
      at a given temperature
2. Unsaturated:
     A solution that contains
      less solute than it can
      hold at a given
3. Supersaturated:
     A solution that contains
      MORE solute than it
      should at a given
F. Suspensions
   (heterogeneous mixture):
  A mixture in which particles are
   dispersed throughout a liquid or
   gas and are large enough that
   they will settle out
  Particles are insoluble – do not
   dissolve, the particles are easily
 Ex. muddy water, snow globes,
  and salad dressing
 The particles in a
  heterogeneous mixture scatter
 Separations of suspensions can
  occur by filtering and settling
G. Colloids:
 A mixture in which the particles
  are dispersed throughout,
  however, they are not large or
  heavy enough to settle out
 The particles are small and are
  very well mixed
 Particles in a colloid cannot be
 filtered or picked out

 Ex. whipped cream, fog

 Colloids scatter light

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