Elements, Compounds and MixturesOh My!

Atoms vs. Molecules

• Review: What is an atom?• The smallest part of an element

• Some atoms are single and other atoms are coupled together.

• When 2 or more atoms are coupled together, they are called molecules.

• What is the difference between atoms and molecules?• Atoms are single (just 1)• Molecules are couples (more than 2 atoms)

Molecules

• Just like elements, molecules are represented by symbols.

• Sometimes molecules are made of atoms that are the same• The oxygen molecule: has 2 atoms of the element oxygen• Symbol: O2

• Sometimes molecules are made of atoms that are different• A water molecule: has 2 atoms of the element hydrogen and 1 atom

of the element oxygen• Symbol: H2O

Pure Substance

• When everything is the same, it is called a pure substance

• All the particles in pure gold are gold atoms.

• All the particles in pure water are water molecules.

Meet the Elements

Elements Are Pure

• If the atoms in a material are all the same (1 type), the material is an element

• Cannot be broken down into simpler substances

• Properties don’t change

• Examples: oxygen, hydrogen, sodium, chlorine, carbon

Compounds Are Pure

• If you have 2 or more elements (different types of atoms) chemically combined = compound

• Can be separated chemically

• The elements that form a compound do not keep their individual properties- • A new substance with completely different properties is formed

• Examples: water, salt, sugar, carbon dioxide gas

Compounds

• Sodium (Na) is a soft metal that explodes when combined with water

• Chlorine (Cl) is a poisonous gas

• But when chemically combined we get an edible, white solid that we know as table salt (NaCl)

• Molecule/compound activity

are always

combine to form

are made of 2 or more

combine to form

are made of 2 or more

can be in the

form of

are always

Mixtures Are Not Pure

• Mixtures are 2 or more substances (can be elements or compounds or both) that are physically together

• The components of a mixture can be separated physically

• Each part of the mixture keeps its individual properties

• Examples: trail mix, salt water (NaCl + H2O)

2 Types of Mixtures

Heterogeneous:• Means "different"• Unevenly mixed

throughout the substance• Pizza• Salsa

• Chicken soup• Chex mix

Homogenous:• Means "the same"• Evenly mixed

throughout the substance• Kool-Aid• Lemonade• Tea/coffee• Salt water

Elements Compounds

Mixtures

• Made of 1 type of atom

• Cannot be separated• Example: Hydrogen

(H), Oxygen (O)

• Made of 2 or more elements

chemically together

• Can be separated chemically

• Examples: Water (H2O)

• Made of 2 or more substances physically together

• Can be separated physically• Example: salt water (NaCl +

H2O)

Pure substances

2 or more substances

Properties don’t change

Matter