Grade 10 Science: Predict – Observe – Explain
Learning Goals:
o Describe what “reactants” and “products” in a chemical equation mean.
o Explain the importance of knowing the difference between "coefficients" and
"subscripts".
o Explain, using the law of conservation of mass and atomic theory, the rationale for
balancing chemical equations
Instructions:
1. Fill plastic bag with 100 mL of vinegar and place sealed plastic bag on scale
2. On a piece of paper towel place a spoon full of baking soda and ensure to fold
the paper towel such that none of the baking soda can be released.
3. Determine the mass of the paper baking soda in the paper towel and the vinegar
in the plastic bag. Record the value in your observations.
4. Carefully place the paper towel in the plastic bag without dropping it in the
vinegar.
5. Seal the plastic bag.
6. Once the plastic bag is sealed, allow the baking soda to drop into the vinegar.
7. Without opening the bag, record the mass of the contents. Take care not to break
the seal of the plastic bag.
Before
you
Observe
1st
After
you
observe
3rd
PREDICT
OBSERVE
Conclusions:
2nd
EXPLAIN
4th
EXPLAIN
Balancing Equations
Step 1. Write out the skeleton __________________.
Step 2. Count the number of _____________of each type in the reactants and products.
Step 3. Ensure Polyatomic ions are counted as ________ item.
Step 4. Multiply the __________________ of the formula by the appropriate number to
balance the number of atoms.
Step 5. Ensure not to change the _______________.
Examples
CH3COOH(l) →
NaHCO3(s) +
CO2(g) +
Reactants
Products
Na:
Na:
H:
H:
C:
C:
O:
O:
Mg +
→
HNO3
H2
Reactants
Products
Mg:
Mg:
H:
H:
N:
N:
O:
O:
+
H2O(l) +
Mg(NO3)2
Do it in your group:
S8
+
O2
→
Reactants
Products
S:
S:
O:
O:
C2H3NaO2(aq)
SO2
Before you leave: EXIT CARD
Name: ____________________________
1. Balance and/or label the following equations (label products, reactants, chemical
names):
a. ___ H2(g) + _____ Cl2(g) → ______HCl(aq)
Reactants
Products
b. ___ N2(g) + ___ H2(g) → ___ NH3(g)
Reactants
Products
c. ___ CH4 + ___ O2 (excess) → ___ CO2 + ___ H2O
Reactants
Products
2. What is Law of Conservation of Mass and explain how the experiment proved this law
(BONUS: provide a real life application)
To extend your learning go to: https://phet.colorado.edu/sims/html/balancing-chemicalequations/latest/balancing-chemical-equations_en.html