Transcript Compounds Galore! - Topsail Middle School

Compounds,
Mixtures,
and
Reactions
Classifying Matter
Matter
Pure Substances
Mixtures
Homogeneous
Elements
Compounds
milk, tea
Fe, O
H2O, CO2
Heterogeneous
Rocky Road ice
cream, muddy
water
What Is A Compound?
A
compound is a pure substance
that is created by 2 or more
elements chemically reacting and
joining together

,
Ex: H2O (water), CO2, NH3 (ammonia) NaHCO3
(baking soda) , and C6H12O6
Why Do Compounds Form?

Compounds form to allow elements to
become more stable


Na (sodium) is flammable when it comes in
contact with H2O, and Cl2 (chlorine) is a toxic gas
NaCl (table salt)is a very stable compound that is
neither flammable nor toxic (in normal quantities)
What Is A Mixture?

A mixture is the physical combination of 2 or
more substances that are not chemically
combined

Mixtures can be divided into 2 groups


Homogenous mixtures
Heterogeneous mixtures
How Do Mixtures Form?



Mixtures form by physically “junking” 2 or
more substances together
Remember no chemical change is occurring
The formation of a mixture is not a result of
lowering energy
What Is a Heterogeneous
Mixture?


A heterogeneous mixture is a mixture that is
unevenly distributed.
Examples:

Chex Mix: You may find a different number of
pretzels or Chex cereal in each handful; therefore,
the mixture is unevenly distributed
What Is a Homogeneous
Mixture?


A homogeneous mixture is a mixture that is
evenly distributed
Homogeneous mixtures are commonly called
solutions.

Solution = Solute + Solvent




Solute: “stuff” being dissolved
Solvent: “stuff” doing the dissolving
The solvent is present in greater quantity
The solute is present in the lesser quantity

Ex: Salt water: Salt=solute, Water=solvent
How Do I Know If A Chemical
Reaction Has Occurred?

There are 5 indicators of a chemical reaction
1.
2.
3.
4.
5.
Evolution of a gas
Evolution of light
Evolution of heat
Color change
Evolution of a precipitate
Precipitate: an insoluble substance that is
produced as result of a chemical reaction
Why Do Chemical Reactions
Occur?

Chemical reactions occur to produce a more stable
product than the existing reactants
Ex: 2Na(s) + Cl2(g)  2NaCl(s)
*The sodium is highly unstable and the chlorine gas is
somewhat unstable. The resulting Sodium Chloride is
VERY stable.
**It is important to understand that the products have totally
different properties than the reactants

Where Does The Matter Go?

It is important to understand that when matter
undergoes a chemical reaction (ie a chemical
change) it does not disappear or appear


The atoms are rearranged and form new bonds,
but no matter is lost nor gained
This is called the Law of Conservation of
Matter