1. Chemical Reactions

2. Physical and Chemical Changes A is any change that does not alter the identity of a substance physical change Matter can change in many ways A occurs when a substance is changed into a new substance chemical change

3. Pop Quiz Question #1 Are these chemical changes or physical changes? ____ sanding a piece of wood ____ melting an ice cube ____ dissolving sugar in water ____ crushing an aluminum can ____ baking bread C P P P P

4. Chemical Equations Any time a reaction takes place it can be represented with a chemical equation CH 4 + O 2  CO 2 + H 2 O Reactants are substances found at the left side of a chemical reaction equation Products are substances found at the right side of a chemical reaction equation Products “yields”

5. Pop Quiz Question #2 During a chemical reaction, reactants always A.Become more complex B.Require catalysts C.Lose mass D.Form products

6. Chemical Reactions During reactions bonds between atoms are broken and new ones are formed CH 4 + O 2  CO 2 + H 2 O Bonds are brokenNew bonds form

7. Evidence of Chemical Reactions Ways to detect whether a chemical changes has occurred: –Temperature change –Formation of a gas –Color change –Formation of a precipitate A precipitate is a substance that forms as a result of a reaction between solid two liquids

8. Pop Quiz Question #3 I see a flame during a chemical reaction. This flame represents A. production of a gas B. a color change C. a temperature change D. formation of a precipitate

9. Conservation of Mass In a chemical reaction atoms are neither created nor destroyed –All atoms present in the reactants are also present in the products Law of conservation of matter/mass: Matter cannot be created or destroyed

10. Chemical Equations and Conservation of Mass Chemical equations represent how atoms are rearranged in a chemical reaction summarize chemical equations show the Chemical equationschemical reactions Balanced conservation of mass

11. Balancing Equations Step 1: List out the atoms and chemical formulas H2OH2O CH 4 +O2O2  CO 2 +

12. Balancing Equations Step 2: Count the number of each atom in the reactants CH 4 + O 2  CO 2 + H 2 O Step 3: Count the number of each atom in the products C=1 H=4 O= 2 C= H= O= 1 3 2

13. Balancing Equations Step 4: Note which atoms are not balanced CH 4 + O 2  CO 2 + H 2 O C=1 H=4 O= 2 C= H= O= 1 3 2 Step 5: Select an atom to balance. Use coefficients to balance. 2 x 2 = 4 2

14. Balancing Equations Step 6: Update atom counts and rebalance 2 x 2 = 4 C=1 H=4 O= 2 C= H= O= 1 4 4 CH 4 + O 2  CO 2 + 2 H 2 O 2

15. Balancing Equations Step 7: Check to ensure all atoms are balanced C=1 H=4 O= 4 C= H= O= 1 4 4 CH 4 + O 2  CO 2 + 2 H 2 O 2

16. Pop Quiz Question #4 Balance the following equation: Al + Fe 2 O 3  Al 2 O 3 + Fe Al=1 Fe=2 O= 3 Al= Fe= O= 2 3 1 2 x 1 = 2 2 2

17. Pop Quiz Question #5 Balance the following equation: Mg + O2  MgO 22

18. Pop Quiz Question #6 NaCl  Na + Cl 2 22 Balance the following equation: