Elements, Compounds, and Mixtures

3 KINDS OF MATTER



Elements



Compounds



Mixtures

Elements

 All (living and nonliving) of the different kinds of matter in the universe is made from about 100 different substances, called elements.

 Elements are called the building blocks of matter because all matter is composed of elements.

 Each element is made up of the same type of atoms.

Compounds

 A compound is a substance made of two or more different kinds of elements chemically combined in a specific ratio.

 Each compound is represented by a formula that uses symbols to identify which elements are present.  A formula shows the ratio of elements in the compound.

 H 2 O – ratio of Hydrogen is 2:1 Oxygen

 The symbols make up the

formula

. A formula is just chemical shorthand for the compound.  The subscript lets us know how many atoms are present.

 The coefficient lets us know how many molecules are present.

Compounds

Molecules

 A molecule is formed when two or more atoms join together chemically.

 Diatomic molecules are made of two atoms of the same element.

 Hydrogen – H 2  Oxygen – O 2

What is the difference between a compound and a molecule?

 A molecule is formed when two or more atoms join together chemically.  A compound is a molecule that contains at least two different elements.  All compounds are molecules but not all molecules are compounds.

 Molecular oxygen hydrogen (H 2 ), molecular (O 2 ) and molecular nitrogen (N 2 ) are not compounds because each is composed of a single element.  Water (H 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ) are compounds because each is made from more than one element.

Molecule

 The smallest bit of each of these substances would be referred to as a molecule. For example, a single molecule of molecular hydrogen is made from two atoms of hydrogen.

 A single molecule of water is made from two atoms of hydrogen and one atom of oxygen.

Mixtures

 Most matter in the universe is found in mixtures.

 A mixture is made from two or more substances either elements, compounds or both - that are not chemically combined.

Mixtures and compounds differ in two ways…

Substances in a mixture keep their individual properties.

Parts of a mixture are not necessarily present in specific ratios.

Compound

 A compound has properties different than the elements that make it up.

 The parts of a compound are present in specific ratio’s.

Compounds and Mixtures

 Most of the matter around you is in the form of compounds or mixtures.

 Water, carbon dioxide, salt, vinegar, baking soda, lye, sugar, gasoline, and bleach are all chemical compounds.

Heterogeneous Mixture

 A mixture in which different materials can be easily distinguished.

 Pizza, dry soup, chex mix, trail mix are all examples.

Solutions

 Homogeneous mixture: is a substance in which two or more substances are uniformly spread out. For example salt water.

 Solution is another term for homogeneous mixture.

Solutions

 Solute is the substance being dissolved.

 Solvent is the substance that dissolves a solute.

 Solubility is the amount of a substance (solute) that will dissolve in a solvent.

Example

 Salt water:  The water is the solvent  NaCl is the solute

Colloids and Suspensions

 A colloid is a heterogeneous mixture that like a solution never settles. Milk and smoke are examples.

 One way to tell a colloid from a solution is because milk is appears white because its particles scatter light. Called the Tyndall Effect.

suspension

 A suspension is a heterogeneous mixture containing a liquid in which visible particles settle.

 River water

NaCl is the formula for salt

Water is H

2

O

 An oxygen atom can bond with two hydrogen atoms to make a molecule we call water. Water is an example of a compound, because it contains more than one kind of atom. The formula for water is H2O, meaning there are two hydrogen atoms for each oxygen atom.

Carbon Dioxide CO

2  Carbon dioxide molecules are made from one carbon and two oxygen atoms joined together by covalent bonds. The chemical symbol is CO2.

Glucose - C

6

H

12

O

6

Molecule

 When a compound is broken down into its’ smallest piece it is called a molecule. You should be able to write the formula for the following:  Water  Oxygen  Carbon Dioxide

DNA

 Is a large molecule made up of carbon, hydrogen, nitrogen, oxygen, and phosphorous.

Kinetic theory of matter

 The idea that all matter is made up of constantly moving tiny particles.

 Elements form compounds to try to fill their outer energy level with valence electrons.

 This is called chemically stable. If the atom is not chemically stable it will lose, share, or gain electrons.  A chemical bond is the force that holds together the atoms in a substance.

Ion

  

An Ion is an atom or group of atoms that has become electrically charged

.

A When an atom loses an electron it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Forming an Ionic Bond:

 . Sodium has one valence electron and transfers that electron to chlorine  Na + Cl- the negative and positive electrical charges attract each other so the oppositely charged ions come together and form sodium chloride (salt).

  .

An ionic bond is the attraction between two oppositely charged ions

. This attraction is similar to the attraction between opposite poles of two magnets.



When two ions come together the opposite charges cancel out.

 Compounds are electrically neutral. When the ions come together they do so in a way that balances out the charges on the ions

Molecules and Covalent Bonds

 The attraction that forms between atoms when they

share

electrons is known as a covalent bond.