Elements, Compounds & Mixtures How everything is put together.

Classification of Matter

Elements  Matter that has the same composition and properties throughout is called an element. When different elements combine, other substances are formed.

Elements  Contains only one particle  Can exist in 3 states of matter solid, liquid, and gas Picture from

Compounds  Ban DHMO?  DHMO is dihydrogen monoxide.  Evaluate the following link and decide if this potentially dangerous chemical should be prohibited. 

Compounds  A compound is a substance whose smallest unit is made up of atoms of more than one element bonded together. Compounds often have properties that are different from the elements that make them up. Examples: Water, salt, sugar

Compounds General Rules: - Only write the name of the metallic element first - Write the number of atoms of any element in the compound in subscript (applies to only 2 or more atoms) - “ide” will always be written at the end of the non metal element

Compound Properties Compounds are formed by atoms of different elements. However, they do not have the properties as them. Because of chemical bonds, compounds cannot be broken down by physical means. They can only be broken down by chemical reaction or electricity.

How do we name compounds? Rule 1 A compound made up of two elements has a name that ends in -ide. Sodium chloride — made up of the elements sodium and chlorine Zinc oxide — made up of the elements zinc and oxygen Carbon dioxide — made up of the elements carbon and oxygen

Fixed Composition of Compounds For example, water (H 2 O) is a compound made only by joining together two atoms of hydrogen to one atom of oxygen. That is, the ratio of hydrogen atoms to oxygen atoms in water is always 2 : 1. A compound is made up of different elements chemically combined in a fixed ratio.

Chemical Formula of a Compound A compound can be represented by a chemical formula. The chemical formula states the types of atoms (i.e. elements) in the compound, the ratio of the different atoms in the compound. Types of atoms: hydrogen, oxygen Ratio of H to O = 2:1

How do we write chemical formula? Rule 1 For many compounds that contain both metallic and non-metallic elements, the symbol of the metallic element is written first. calcium oxide (CaO) sodium chloride (NaCl) magnesium carbonate (MgCO 3 )

How do we write chemical formula? Rule 2 The number of atoms is written as a subscript, to the right of the atom’s symbol. water (H 2 O, not H2O or 2HO) magnesium carbonate (MgCO 3, not MgCO 3 or MgC 3 O)

How do we write chemical formula? Rule 3 It is not necessary to write the subscript ‘1’. water (H 2 O, not H 2 O 1 ) calcium oxide (CaO, not Ca 1 O 1 )

How do we write chemical formula? Rule 4 The oxygen atom is usually written at the end of the formula. water (H 2 O, not OH 2 ) carbon dioxide (CO 2, not O 2 C) nitric acid (HNO 3, not O 3 NH)

Let’s try it…  How many atoms of each element are there in the compound?  Sulfuric AcidH 2 SO 4  __ Hydrogen  __ Sulfur  __ Oxygen  Hydrogen Peroxide H 2 O 2  __ Hydrogen  __ Oxygen

And some more formulas…  Carbon Dioxide CO 2  __ Carbon  __ Oxygen  Carbon Monoxide CO  __ Carbon  __ Oxygen  Calcium Carbonate CaCO 3  __ Calcium  __ Carbon  __ Oxygen

Compound Review  A pure compound has the same elements and the same amount of elements all of the time EElements are chemically combined CCompound properties are different from the properties of the elements TThey cannot be separated physically PPhysical properties such as boiling point or melting point of pure substances are 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

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, it is the universal solvent.

Examples of solutions  Salt water  Clean Air  Vinegar List 3 solutions and name the solute and solvent.

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  Sandwich  Chex Mix List 4 examples of your own

Suspensions  A SUSPENSION is a heterogeneous mixture of large particles  These particles are visible and will settle out on standing  Examples of suspensions are: fine sand or silt in water or Italian salad dressing

Classification of Matter

Compounds vs Mixtures CompoundsMixtures Combine chemically forming molecules Not chemically combinedNot chemically combined Combine in set proportions Can combine in any proportionCan combine in any proportion Separated chemically Separated physicallySeparated physically

What is it? Trail Mix

Heterogeneous

What is it? Kool - Aid

Homogeneous

What is it? Water

Homogeneous

What is it? White Vinegar

Homogeneous

What is it? Italian Salad Dressing

Heterogeneous

Try these……….. Raisin Bran

Orange Juice

Air

Chunky Soup

Hamburger

Cake Batter

Paint

Salad

Mineral Rock

Answers:  Raisin Bran – heterogeneous  Orange Juice – homogeneous  Air – heterogeneous  Chunky Soup – heterogeneous  Hamburger – heterogeneous  Cake Batter – homogeneous  Paint – homogeneous  Salad – heterogeneous  Mineral Rock - heterogeneous