1. Mixtures, Elements, CompoundsCh
Mixtures, Elements, Compounds

2. Symbols Chemists use chemical symbols to represent elements
Chemical Symbol: 1st 1-2 letters of the name of the element
1st letter is always Capitalized
2nd letter is always lower case
Examples: Co = Cobalt; O = Oxygen;
Be = Berylium
Exception: Some use the letters from the Latin name
Examples: Fe = Iron (Ferrum)
K = Potassium (Kalium)
Cu = Copper (Cuprium)

3. Formulas Chemists use chemical formulas to represent compounds
Compounds: 2 or more elements
Examples: NaCl = Sodium Chloride
H2O = Water

4. Breaking up
Compounds can be broken down into simpler substances by chemical means, but elements cannot
Chemical changes can be used to break down the substances
Heating sugar can be heated until it breaks down into solid carbon and water vapor

5. “Heating sugar can be heated until it breaks down into solid carbon and water vapor”
Do you think either of those substances that are formed can be broken down any?
Yes, the water can be broken down into hydrogen and oxygen 

6. Properties
Properties of compounds differ greatly from the properties of the individual elements that make them up
Solid sodium is extremely reactive
Chlorine is a gas
Combined they make up sodium chloride, aka table salt

7. Na + Cl2  NaCl Sodium + Chlorine  Table salt

8. H2 + O2  H2O

9. Classifying mixtures
A mixture is a physical blend of two or more components
Based on the distribution of the components, mixtures can be classified as heterogeneous or homogeneous mixtures

10. Heterogeneous mixture: a mixture in which the composition is not uniform throughout
Ex: oil and vinegar, sand in water
Homogeneous mixture: a mixture in which the composition is uniform throughout
Also known as a solution

11. Homogeneous mixtures
Many solutions are liquid, but can also be gas (air) or solids (stainless steel)
The term “phase” can be used to describe any part of a sample with uniform composition and properties
Homogeneous mixtures have 1 phase

12. Heterogeneous V. Homogeneous

13. Distinguishing Substance and Mixtures

14. Separating mixtures
Different physical properties can be used to separate mixtures
Different BPs or MPs can be used
Filtration: separates a solid from a liquid
Coffee filters separate grounds from water
Distillation: a liquid is boiled to produce a vapor then condensed into a liquid

16. Paper chromatography Separating a mixture

17. Chemical reactions
Chemical changes are signs of chemical reactions happening
Iron reacting with oxygen to form rust
Fe + O2  Fe2O3
During a chemical reaction, the composition of matter always changes

18. A substance produced in the reaction is the “product”
Fe + O2  Fe2O3
A substance present at the start of a chemical reaction is called a “reactant”
A substance produced in the reaction is the “product”
Reactants react to produce products

19. Recognizing chemical reactions
Signs a reaction may have occurred:
Production of gas or bubbles
Change in color
Change in temperature
Precipitate forms
A solid that forms and settles out of a liquid mixture

20. Law of Conservation of Mass
During any chemical reaction or physical change, the mass of the products is always equal to the mass of the reactants
Bottom line: you cannot create or destroy matter. Matter is conserved.

21. Discuss
What about burning a candle? Where does the mass go??

22. Review questions How are mixtures classified?
Come up with a way to separate a mixture of sand and salt
How is a compound different from an element?
How much water would form if 4.8 grams of hydrogen reacted with 38.4 g oxygen?