1. Now try this! Compounds

2. Which of these are chemical reactions? Melting Ice Boiling water Burning Carbon Lighting Fireworks Baking bread

3. Compounds Which of these are compounds and which are elements? Sodium Sodium Chloride Iron Iron and sulfur Iron sulfide Rust Sugar Carbon

4. Compounds! Now try to test your knowledge of reactions of elements. What compound will be formed when...? Zinc reacts with oxygen? Iron reacts with chlorine? Hydrogen reacts with sulfur? Magnesium reacts with bromine?

5. Molecules Compounds are made of molecules Molecules are two or more atoms chemically combined Molecules are the smallest particle of a compound that has all the properties of that compound

6. H H Water Molecule Water is a compound made of two 2 atoms of hydrogen and 1 atom of oxygen. One molecule of water has the same properties as a bucket full of water O

7. Chemical Formulas Chemical formulas are combinations of chemical symbols Short way to represent chemical substances Most chemical formulas represent compounds

8. Examples of Chemical Formulas Ammonia: 1 atom of nitrogen, 3 atoms of hydrogen Chemical formula = NH 3 Silver nitrate: 1 silver, 1 nitrogen, 3 oxygen Chemical formula = AgNO 3 Carbon dioxide: 1 carbon, 2 oxygen Chemical formula = CO 2

9. Molecules of elements Sometimes elements are found in nature as molecules Hydrogen = H 2 Oxygen = O 2 Nitrogen = N 2 Chlorine = Cl 2 HH Drawing chemical formulas Hydrogen oxygen oo NN Nitrogen Cl Chlorine

10. Subscripts The small numbers you place to the right of the symbol. Must be placed lower EX: C 2 H 4 O 2 Gives the number of atoms of the element in the compound. 2 carbon, 4 hydrogen, 2 oxygen If there is only 1 atom, the subscript is not written. Example: NaHCO 3

11. Practice counting atoms List the elements in each of the following compounds. Calculate how many atoms of each element are present. 1. NaHCO 3 5. 2H 2 SO 4 2. C 2 H 4 O 2 6. (NH 4 ) 3 PO 4 3. Mg(OH) 2 7. C 6 H 12 O 6 4. 3H 3 PO 4 8. 4CaCO 3

12. Chemical Equations Used to describe a chemical process or reaction Charcoal burning is a chemical reaction 1 Carbon atom plus 1 oxygen atom produces carbon dioxide molecules OR - C + O 2 CO 2

13. oo Look at Chemical Equations - C + O 2 CO 2 - This says that 1 carbon atom and an oxygen molecule create carbon dioxide - The arrow means produces - C oo C

14. Another Chemical Equation H 2 + O 2 H 2 O H 2 + O 2 H 2 O 1 hydrogen molecule combines with 1 oxygen molecule to produce water. 1 hydrogen molecule combines with 1 oxygen molecule to produce water. Problem with the equation—what is it? Problem with the equation—what is it? Numbers do not balance on each side Numbers do not balance on each side Look at the oxygen atom Look at the oxygen atom

15. Correcting the water equation H 2 + O 2 H 2 O There are 2 hydrogen atoms on each side so that is correct There are 2 oxygen atoms on the left side, but only one on the right side. You need to balance both sides 2H 2 + O 2 2H 2 O Now there are even number of atoms on each side (4 hydrogen, 2 oxygen)

16. Coefficient Those numbers we added to the front of the formula is called the coefficient. This is how you balance an equation.

17. Lets try another one P 4 + O 2 P 2 O 3 How many phosphorous atoms on each side? 4 on the left, 2 on the right How many oxygen atoms on each side? 2 on the left, 3 on the right What can we do to balance it? P 4 + 3O 2 2P 2 O 3

18. Let’s practice again N 2 + H 2 NH 3 How many nitrogen and hydrogen atoms on each side? Left: 2 nitrogen and 2 hydrogen Right: 1 nitrogen and 3 hydrogen How can we balance it? N 2 + 3H 2 2NH 3

19. another—you WILL understand this AlBr3 + K KBr + Al What elements are involved? Aluminum, bromine and potassium How many atoms of each element are on each side of the equation Left side: 1 aluminum, 3 bromine, 1 potassium Right side: 1 potassium, 1 bromine and 1 aluminum

20. So the answer to the question What is the balanced equation AlBr 3 + 3K 3KBr + Al How many atoms of each element are there now on each side Left side: 1 aluminum, 3 bromine, 3 potassium Right side: 3 potassium, 3 bromine and 1 aluminum

21. Now for a harder one LiNO 3 + CaBr 2 Ca(NO 3 ) 2 + LiBr What atoms are involved? Lithium, nitrogen, oxygen, calcium, bromine How many atoms on each side? Left: 1 Li, 1 N, 3 O, 1 Ca, 2 Br Right: 1Ca, 2 N, 6 O, 1 Li, 1 Br

22. What is the balanced equation 2LiNO 3 + CaBr 2 Ca(NO 3 ) 2 + 2LiBr How many atoms are there now? 2 Li, 2 N, 6 O, 1 Ca, 2 Br on each side.

23. THE END