1. Chemical Changes Monroe 1-9-09

2. What are the parts to a chemical formula? Coefficient Atoms Subscripts

3. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of compound. It always goes on the front. Subscripts ~ Element Compound

4. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of the compound. It always goes in the front. Subscripts ~ Tells the number of atoms in the compound. Subscript means “below writing”. Element ~ Compound

5. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound

6. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

7. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

8. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound ~ Tells what combination of atoms, chemically combined, you are looking at. C 8 H 10 N 4 O 2 This is a compound

9. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound ~ Tells what combination of atoms, chemically combinded, you are looking at. C 8 H 10 N 4 O 2 This is a subscript

10. What are the parts to a chemical formula? Coefficient ~ Tells the number of units of substance. Subscripts ~ Tells the number of atoms in the compound Element ~ Tells the type of atom in the compound Compound ~ Tells what combination of atoms, chemically combined, you are looking at. C 8 H 10 N 4 O 2 This is an element

11. What do they tell us? They tell us how different chemicals will combine with each other.

12. O 2 + H 2 H 2 O + heat What is very, very wrong with this equation?

13. What do they tell us? They tell us how different chemicals will combine with each other. O 2 + H 2 H 2 O + heat It is NOT balanced. Oxygen21 Hydrogen22

14. What do they tell us? They tell us how different chemicals will combine with each other. O 2 + H 2 H 2 O + heat O 2 + 2H 2 ---> 2H 2 O + heat Oxygen22 ------------------------------------------------------------ Hydrogen44 (Always multiply the coefficient and the subscript)

15. Some important things to remember. 1.The stuff on the left is the reactants 2.The stuff on the right is the products 3.The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass.

16. Some important things to remember. 1.The stuff on the left is the reactants 2.The stuff on the right is the products 3.The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass. 4 g of Hydrogen + 32 g Oxygen = 36 g Water O 2 + 2H 2 ---> 2H 2 O + heat

17. Balancing equations 1.Solid magnesium burns with gaseous oxygen to make solid magnesium oxide. 2.Step one is to write out the sentence with chemical symbols, according to what actually happens. Mg (s) + O 2(g) --> MgO (s) + energy Step two is to choose coefficients that balance the number of atoms on each side, but never, never ever change the subscripts. If you change the subsript, you are saying that something else is being made. 2Mg (s) + O 2 (g) --> 2MgO (s) If there is no coefficient, or subscript, it is a “one”.

18. Hydrogen gas burns with oxygen to make liquid water, and excess energy. Hydrogen gas and oxygen gas are always O 2 and H 2.

19. H 2(g) + O 2(g) ---> H 2 O (l) + energy

20. Hydrogen peroxide (H 2 O 2 ) liquid decomposes into oxygen gas and water, if energy is added to the equation.

21. H 2 O 2 + energy --> H 2 O + O 2

22. Hydrogen peroxide (H 2 O 2 ) liquid decomposes into oxygen gas and water, if energy is added to the equation. H 2 O 2 + energy --> H 2 O + O 2 2H 2 O 2 + energy --> 2H 2 O + O 2

23. Butane gas (C 3 H 8 ) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.

24. C 3 H 8 + O 2 ---> CO 2 + H 2 O + energy

25. Butane gas (C 3 H 8 ) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy. C 3 H 8 + 5O 2 ---> 3CO 2 + 4H 2 O + energy

26. Photosynthesis is when sugar, C 6 H 12 O 6 and O 2 combine to make carbon dioxide and water. C 6 H 12 O 6 + O 2 --> CO 2 + H 2 O

27. Photosynthesis is when sugar, C 6 H 12 O 6 and O 2 combine to make carbon dioxide and water. C 6 H 12 O 6 + 6O 2 --> 6CO 2 + 6H 2 O