1. COMPOUNDS AND MIXTURES
Lesson 11 Notes

2. Elements combine with other elements
Over 100 known elements.
Elements are pure substances and can’t be separated by physical means
Most substances in the world are not just 1 elements
Elements combine in different ways to form new substances /molecules

3. CHEMICAL FORMULAS
A chemical formula is a group of chemical symbols and numbers ( in subscript) that show the type and number of atoms in a molecule.
If there is no number then it is just 1 atom
Example: OH ( 1 oxygen and 1 hydrogen)

4. COMPOUNDS
Pure substances that are formed when 2 or more DIFFERENT ELEMENTS join together chemically (bond)
Example: 2 H and 1 O = H20 (water)
Example: 1 Na and 1 Cl = NaCl (salt)
Example: 6 C and 12 H and 6 O = C6H12O6 (glucose)
Example: 2 Fe and 3 O = Fe2O3 (iron oxide , rust)

5. COMPOUNDS
Are new substances that are made up of one kind of a new molecule
Molecules are groups of 2 or more atoms held together by very strong chemical bonds.
Bonds form when atoms share or give away(transfer) valence electrons
Example: rust is no longer iron or oxygen, it is a new substance called rust

6. COMPOUNDS ARE NEW SUBSTANCES
The properties of compounds are different than the properties of the elements that make them up
Example: H2O
liquid at room temp where H and O are gases at room temp
Water doesn’t burn but H does

7. Mixtures
Are combinations of 2 or more substances that are not joined chemically
Mixtures are not pure substances
The parts of the mixture keep their own identities and properties – they DON’T MAKE NEW SUBSTANCES
Example: sugar and salt mixed together
Sugar still sweet, salt still salty

8. MIXTURES CAN BE SEPARATED BY PHYSICAL PROPERTIES
Physical properties can be used to separate mixtures
Particle size ( large, medium, small – filter with different sized filters)
Texture (fine, smooth, rough)
Density ( sinks if more than water or floats if less than water)
Solubility( dissolves in water)
Boiling point(evaporate)
Attracted to magnet