Chemical Reactions

DEMONSTRATIONS OF CHEMICAL REACTIONS – LINKED ON THE WIKI

Temperature Changes Endothermic ABSORBS Energy Gets COLD Exothermic RELEASES Energy Gets HOT or gives off LIGHT Two types of reactions:

Chemical Equation Subscripts Yield Sign

What are coefficients and subscripts? Circle the subscript. Draw a square around the coefficient. CaF 2

What do coefficients mean? CaF 2

What do subscripts mean? CaF 2 How many Ca ions? How many F ions?

Time for a WS! Parts & Pieces WS

Step ONE Step 1: Draw a line, separating reactants from products. CH 4 + O 2  CO 2 + H 2 O

Step TWO Step 2: Write down the elements on EACH SIDE of the line (IN THE SAME ORDER). CH 4 + O 2  CO 2 + H 2 OCHO

Step THREE Step 3: Count the atoms of each element on BOTH SIDES of the line CH 4 + O 2  CO 2 + H 2 O C - 1C - 1 H - 4H - 2 O - 2O - 3

Step FOUR Step 4: Start on the side with FEWER atoms. CH 4 + O 2  CO 2 + H 2 O C - 1C - 1 H - 4H - 2 O - 2O - 3 There are fewer HYDROGEN atoms on the right, so we’ll start on that side.

Step FIVE Step 5: Write in a coefficient of TWO. Then, re-count the atoms of EACH element on that side. CH 4 + O 2  CO 2 + 2H 2 O C - 1C - 1H - 4 O - 2O - 4 Now the Hydrogens match. Repeat step 4-5 until ALL of the elements match!

Repeating Steps 4-5 Step 4: Fewer Oxygens on LEFT Step 5: Add coefficient of TWO & re- count. CH 4 + 2O 2  CO 2 + 2H 2 O C - 1C - 1H - 4O - 4 Now they all match!

FINAL EQUATION CH 4 + 2O 2  CO 2 + 2H 2 O WARNING: NEVER CHANGE SUBSCRIPTS!! NEVER ADD A COEFFICIENT IN THE MIDDLE OF A FORMULA!!

Try another one! Go on to the next slide to see the answer! CO 2 + H 2  CH 4 + H 2 O

Did you get it right? CO 2 + H 2  CH 4 + H 2 O CO 2 + H 2  CH H 2 O

Try one more! Go on to the next slide to see the answer! Fe + O 2  Fe 2 O 3

Did you get it right? 4Fe + 3O 2  2Fe 2 O 3 Let’s do a WS! This is BALANCING EQUATIONS!