Transcript Mixtures and Compounds

Mixtures, Compounds,
and Chemical Changes
Compounds
• Compound: A pure substance consisting of
two or more elements combined.
• Water - H2O (liquid)
• Salt - NaCl (solid)
• Methane - CH4 (gas)
Chemical Change
• A chemical reaction is required to separate a
compound into separate parts.
• Chemical Reaction: Any change that involves
the formation of a new substance.
– Formation of precipitate
– Change in color
– Formation of gas
– Temperature change
Chemical Change
• A chemical change consists of two parts.
– Product: A substance formed by a chemical
reaction.
– Reactants: The starting substances in a chemical
reaction.
2 H2O
2 H2 + O2
Reactants
Products
Chemical Change
• Cake Recipe:
– Flour, Eggs, Sugar, Chocolate, etc.
– Beat together
– Bake
• Once baked, the ingredients are very difficult
to separate!
Chemical Change
What chemical reactions occur in everyday life?
• Photosynthesis:
– 6 CO2 + 6 H2O + light
C6H12O6 + 6 CO2
• Combustion:
– C3H8 + 5 O2
4 H2O + 3 CO2 + energy
• Rust:
– 4 Fe + 3 O2 + 6 H2O
4 Fe2O3.nH2O
Mixtures
• Mixture: Two or more elements that are
mixed together but are not chemically
combined.
• Mud - H2O + Dirt (Fe, K, Ca)
• Salt Water - NaCl + H2O
• Salad
Mixtures
• Mixtures combine physically with no specific
proportions. They just mix.
• Solids, liquids, and gasses can be combined to
create mixtures.
• When creating a mixture, no new substances
are formed. Each part of the mixture keeps its
own properties.
Mixtures
• Homogeneous Mixture: A mixture with the
same uniform appearance and composition
throughout.
– “Homo” prefix meaning same
• Heterogeneous Mixture: A mixture consisting
of visibly different substances or composition.
– “Hetero” prefix meaning different
Can you come up with some examples?
Mixtures
• Simple mixtures can easily be separated by
physical means.
• Simple Mixtures:
– Sand, Dust, Italian Dressing
• Mixtures can be separated in a variety of
ways.
– Weight (centrifuge), Evaporation, Sifting,
Magnetism.