1. Chemical Reactions

2. Chemical Reactions are all around us

3. Describing Chemical Reactions
chemical change - rearrangement of atoms to form a new substance
Has new chemical and physical properties

4. Evidences of a Chemical Reaction
Produce a gas
Produce a solid (precipitate)
Color change
Odor change
Temperature change
Exothermic
Endothermic
Give off heat/light
Produce sound

5. Chemical Reaction vs. Physical Change
To prove a chemical change took place, you have to do a chemical analysis
Properties of a new substance must differ from the original substance

6. made + steps  stampedes
Analogy!
Physical change is like printing a word in a different font, it’s the same word just looks different!
stampedes  stampedes
Chemical change is like scrambling letters to form new words
made + steps  stampedes

7. Remember… All changes of state: Solid Liquid  Gas Are Physical
Evaporation
Condensation
Melting
Freezing
Are Physical
Changes!

8. Physical or Chemical Change?

9. Physical or Chemical Change?

10. Physical or Chemical Change?

11. Physical or Chemical Change?

12. Physical or Chemical Change?

13. Physical or Chemical Change?

14. Physical or Chemical Change?

15. Physical or Chemical Change?
Rotten Egg

16. Physical or Chemical Change?

17. Physical or Chemical Change?

18. Physical or Chemical Change?

19. Physical or Chemical Change?

20. Physical or Chemical Change?

21. What causes Chemical Reactions?

22. Reaction and Energy Changes
Chemical Reactions either RELEASE or ABSORB energy.

23. Release Energy Example:
Natural Gas
Methane + Oxygen  Carbon Dioxide + Water + ENERGY

24. Absorb Energy Example:
Photosynthesis
Carbon Dioxide + Water + ENERGY  Oxygen + Glucose

25. Chemical Equations Equations are used to represent chemical reactions
Reactants – starting substances
Products – new substances
Reactants Product

26. Chemical Equations Arrow always points to the product
Hydrogen + Oxygen Water
Mercury Oxide Liquid Mercury Oxygen
Sodium Chloride Sodium + Chlorine

27. Word Equations – uses names
Names of the reactants separated by a +
Arrow separates reactants from products
Names of products separated by a +
Example:
Hydrogen + Oxygen Water

28. Formula Equations – uses symbols
Symbol of the reactants separated by a +
Arrow separates reactants from products
Symbol of the products separated by a +
Example:
H₂ + O₂ H₂O

29. Writing word and formula equations:
Mercury oxide is heated to form liquid mercury and oxygen
Word =
Formula =

30. Common symbols in equations
→ : produces or forms
+ : plus
(s) : solid
(l) : liquid
(g) : gas
(aq) : aqueous - dissolved in water

31. Add the symbols Hydrogen + Oxygen Water Mercury Oxide Mercury + Oxygen
Sodium Chloride Sodium + Chlorine

32. Common symbols in equations
Reversible
1803 a scientist observed the formation of sodium carbonate crystals at the edge of a salt lake 2NaCl + CaCO3 → Na2CO3 + CaCl2. He recognized this as the reverse of the familiar reaction Na2CO3 + CaCl2→ 2NaCl + CaCO3. He reasoned that the excess of salt in the lake helped push the "reverse" reaction towards the formation of sodium carbonate

33. Common symbols in equationsKI
______ The element symbol above the arrow indicates a catalyst.
A catalyst is something that speeds up the reaction but is not changed during the reaction, so it goes above the arrow.

34. Review writing ionic compounds
Magnesium Nitride
Iron (III) Oxide
Sodium Sulfide
Copper (II) Chloride

35. Seven diatomic elements:
Hydrogen (H2)
Nitrogen (N2)
Oxygen (O2)
Fluorine (F2)
Chlorine (Cl2)
Iodine (I2)
Bromine (Br2)
Write these on back of periodic table!

36. Common Polyatomic Ions
Write these down on the backs of your periodic tables

37. Writing polyatomic compounds
Aluminum Hydroxide
Mercury (II) Phosphate
Aluminum Sulfate
Copper (II) Bromide
Lead (II) Chlorite
Silver Cyanide
Ammonium Oxide