Substances, Compounds & Mixtures

How everything is put together.

Substances

Matter that has the same composition and properties throughout is called a substance.

• When different elements combine, other substances are formed.

Substances

Contains only one particle

Can exist in 3 states of matter

Can be elements or compounds

Picture from http://www.ilpi.com/msds/ref/gifs/statesofmatter.gif

What is a Pure Substance?•A pure substance is a classification of matter that includes both elements and compounds•Pure substances cannot be separated by physical means such as distillation, filtration, or chromatography

Compounds

Are made of molecules and molecules are the smallest particle of a compound

• Have properties that are different from the elements that make them up.

• Molecules made up of 2 or more atoms chemically bonded together

• Examples: Water, salt, sugar

•A substance whose smallest unit is made up of atoms of more than one pure element bonded together.

H2O is the chemical formula for water, and H2O2 is the formula for hydrogen peroxide.

The formula tells you which elements make up a compound as well as how many atoms of each element are present.

Compounds Have Formulas

How to read a formula

HH2200 This is a subscript. It tells us how many atoms of that element exist in one unit of that compound. Water is made of 2 H atoms and 1 O atom. No subscript is used when only one atom of an element is present.

Compounds

Sugar Carbon, Hydrogen, Oxygen (C12 H22 O12)

12 Carbon atoms + 22 Hydrogen atoms + 12 Oxygen atoms = 1 molecule of sugar

Compounds

Water Hydrogen, Oxygen (H2 O)

Salt Sodium, Chlorine (Na Cl)Hydrogen Peroxide Hydrogen, Oxygen (H2 O2)

Compound Review A pure compound has the same elements

and the same amount of elements all of the time

Elements are chemically combined Compound properties are different from the

properties of the elements They cannot be separated physically Physical properties such as boiling point or

melting point of pure substances do not change

Mixtures

A mixture is a combination of two or more substances where there is no chemical combination or reaction.

Mixtures combine physically in no specific proportions.They just mix.

Solids, liquids and gases can be combined to

create a mixture.

Mixture Types

MIXTURES MAY BE HOMOGENEOUS OR HETEROGENEOUS

Homogeneous Mixtures Homogeneous Mixtures: The prefix: "homo"- indicates the

same Have the same uniform appearance

and composition throughout EX. A pile of pennies, iced tea with

sugar (sugar has dissolved)

Solutions SOLUTIONS are homogeneous mixtures

What is a solution? A solution is a mixture of

two or more substances. At least two substances

must be mixed in order to have a solution

A solution has two parts The substance

in the smallest amount and the one that DISSOLVES is called the SOLUTE

The substance in the larger amount is called the SOLVENT - it does the dissolving IN most common instances water is the solvent

                        

Examples of solutions

Salt water Clean Air Vinegar

Heterogeneous Mixtures:

The prefix: "hetero"- indicates difference

A heterogeneous mixture consists of visibly different substances or phases

Two or more parts can be seen

Examples:

Pizza A pile of coins

Chex Mix

How Can We Change Matter Into New Substances?

Chemical reaction (also known as a chemical change) is a change in a substance or substances

that results in a totally new substance Ex: 2H2(g) + O2(g) 2H2O(l)

Notice that the reactants (the substances you start with) combine to form a new substance (the

product)

How Do I Know If A Chemical Reaction Has Occurred?

There are 5 indicators of a chemical reaction

1. Evolution of a gas2. Evolution of light3. Evolution of heat4. Color change5. 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

Structure of a Chemical Equation A chemical equation tells you the substances

you start with in a reaction and the substances you get at the end

The substances at the beginning are called the Reactants.

When the reaction is complete, you have new substances call the Products

The number of reactants and products can vary

Structure of a Chemical Equation

Reactant + Reactant Product + Product Reactant + Reactant yields Product

NH3 + HCl NH4Cl

Ammonia + Hydrogen Chloride yields Ammonium Chloride

Structure of a Chemical Equation

Reactant Product + Product Reactant yields Product + Product

CaCO3 CaO + CO2

Calcium Carbonate (heated Limestone- 1,517oF) yields Calcium Oxide + Carbon Dioxide

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

Compounds vs MixturesCompoundsCompounds MixturesMixtures

Combine chemically forming molecules

Not chemically Not chemically combinedcombined

Combine in set proportions

Can combine in any Can combine in any proportionproportion

Separated chemically Separated Separated physicallyphysically

Classifying Matter

Matter

Pure Substances Mixtures

Elements Compounds Homogeneous Heterogeneous

Fe

O

H2O

CO2

Milk

tea

Rocky Road ice cream, muddy water