Pure Substances & Mixtures

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Pure Substances
& Mixtures
What is a
pure substance?
Pure Substance
 A substance in which there is only one
type of particle.
 The particles of a pure substance are
alike no matter where they are found.
 Ex: Particles of iron in a skillet are the same as the
iron particles found in a meteorite
Element
 Is a pure substance that cannot be
separated into simpler substances by
physical or chemical means.
 It only has one type of atom.
Compounds
 A pure substance composed of two or
more elements that are chemically
combined.
 Salt- Sodium & Chlorine
 Water- hydrogen & oxygen
 Sugar- carbon, hydrogen
& oxygen
 Baking soda- sodium,
hydrogen, carbon, and oxygen.
Compounds aren't
Random
 The elements that make up a compound join in
a specific ratio according to their masses.
 Water
 2 atoms of hydrogen to 1 atom of oxygen (2:1 ratio)
 1g hydrogen to 8g oxygen = 1:8 = 1/8
 Each compound has its own set or identifying
properties different from the elements that it is
formed from.
What is a
mixture?
Mixture
 Is a combination of two or more
substance that are not chemically
combined.
 The substance in a mixture retain their
identity.
 Ex: pizza, salt water
Solutions
 Are mixtures that appear to be a single
substance.
 They are still composed of two or more
substance but they are distributed evenly
amongst each other
Parts of a Solution
 Solute- The substance that is dissolved
 Ex: salt
 Solvent- The substance in which the solute is
dissolved in.
 Ex: Water
 Salt is soluble in water
 When two liquids or gasses for a solution the
substance of greater volume is the solvent.
 Aqueous Solution – a solution in which
water is the solvent.
 Electrolyte – a solution that conducts
electricity.
 Nonelectrolyte – a solution that does not
conduct electricity.
 Saturated solution – when the solvent
can not hold anymore solute.
Three factors that speed up dissolving:
- temperature
- stirring
- particle size
More on Mixtures:
 Concentration: measures the amount of a
solute dissolved in a solvent.
 Solutions can be described as being concentrated or
diluted.
 Solubility: The amount of solute needed to
make a saturated solution ( grams/ 100mL)
 Saturated: A solution that contains all the solute is can hold
at a given temperature.
 Unsaturated: A solution that contains less solute then it can
hold at a given temperature.
Types of Mixtures:
 Suspensions: A mixture in which particles or a
material are dispersed throughout a liquid or
gas but are large enough that they settle out.
 Colloids: A mixture in which
particles are dispersed throughout
but are not heavy enough to settle out.
Ex: Milk, Jell-O, Fog
They cannot be separated by
filtration the particles are too small
Mixtures Vs. Compounds
Mixtures
Compounds
Components are elements,
compounds, or both.
Components are elements.
Components keep their
Components lose their
original properties.
original properties.
Separated by physical means. Separated by chemical means.
Formed using any ratio of
components
Formed using a set mass ratio
of components.
Mixtures are Either:
 Homogeneous: Have the same
appearance and properties throughout
the mixture
 Ex: Solutions- milk, Kool-Aid
 Heterogeneous : the different
components are easily seen.
 Ex: suspensions- salad dressing, muddy water.
Yet Another Way To
Classify Matter
How do you separate a
mixture?
 By:
Physical separation (take topping off pizza)
Distillation (based on boiling points)
A magnet (certain metals)
A centrifuge (separates by density)
Filter (solid particles)
Evaporation (sodium chloride & water)
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