1. Daily TAKS Connection: Conservation of Mass
IPC(8) The student knows that changes in matter affect everyday life. The student is expected to:
(C) investigate and identify the law of conservation of mass

2. Day 1: Construct a folded book foldable
Instructions:
Hamburger fold the foldable handouts
Cut 2 cm slits from the edges of the fold of the handout that has page 2 (as marked)
Cut along the fold line of the other sheet of paper beginning and ending about 2 cm from each end (as marked).
Burrito fold and insert paper from step 2 into the hole and open, forming a book.
Color the front cover
Construct a folded book foldable titled “Conservation of Mass”
Materials:
Foldable handout (2 pages)
Scissors
Pen
Colored pencils/crayons

3. Day 2 Notes (record on page 1 of foldable):
atoms are neither created or destroyed in a chemical reaction
atoms are rearranged in a chemical reaction
Student Task: Label the “Reactants” and the “Products” in the boxes provided above the diagram on page 1 of your foldable.
Image source:

4. Day 2 Notes continued (record on page 2 of foldable):
Rule:
to support the Law of conservation of mass, the “mass of reactants must equal the mass of products”

5. Question
If all the reactants in a chemical reaction are completely used, which of the following statements accurately describes the relationship between the reactants and the products?
a. The products must have a different physical state than the reactants.
b. The total mass of the reactants must equal the total mass of the products.
c. The reactants must contain more complex molecules than the products do.
d. The density of the reactants must equal the density of the products.
Answer: B

6. Question
2H20 →
2H2 + O2
The chemical equation shows H20 being decomposed. Which of these statements best describes the mass of the products if 150 g of H20 is decomposed?
a. The mass of each product is equal to the mass of the H20.
b. The sum of the products’ masses is 150 g.
c. The sum of the products’ masses equals the mass of the H20.
d. Both b and c.
Answer: D.

7. Question
In the procedure shown, a calcium chloride solution is mixed with a sodium sulfate solution to create the products shown. Which of the following is illustrated by this activity? a. The law of conservation of reactants b. The law of conservation of products c. The law of conservation of mass d. The law of conservation of energy
Answer: C. Clue from picture – mass of reactants and products = g.

8. Day 3: Notes (record on page 3 of foldable)
When a chemical reaction takes place and
mass appears “lost”, a gas is probably a product and dissipates into the atmosphere
mass appears “gained”, other atoms were introduced into the system and reacted with

9. Question
Which of these would support the idea that mass is conserved in a reaction that produces a gas as a product?
a. Heating the reactants to ensure the reaction occurs in a gaseous state
b. Subtracting the mass of the gas from the mass of the solid and liquid products
c. Mixing the reactants and measuring their total mass
d. Trapping the gas and measuring its mass
Answer: D.

10. Question
The mass of a rusty nail is found to be slightly greater than the mass of the same nail before it rusted. The change in mass indicates that the rusting process —
a. is a physical change
b. involves an energy-to-matter conversion
c. decreases the density of the metal
d. involves metal bonding with other atoms
Answer: D

11. Question
The illustrations show a conservation-of-mass experiment. The solution in the beaker lost mass because —
a. materials have less mass at high temperatures
b. the mass of the reactants and products was less than 100 g
c. sodium sulfate (Na2SO4) is lighter than air
d. some of the water molecules turned into water vapor
Answer: D. Due to the large amount of heat (shown on illustration), water likely evaporated.

12. Day 4 Notes – record on page 4 of the foldable
List the atoms found in a chemical formula.
an atom is indicated by an uppercase letter
Example: H – Hydrogen OR
an uppercase letter followed by a lowercase letter
Example: Hg – mercury
Determine the number of each atom type.
Subscript multiplied by coefficient
Example:
2H20
Point out to students that even though a subscript of 1 is not written for the O atom, it is implied. H
subscript 2 x coefficient 2 =
4 atoms total O
Subscript 1 x coefficient 2 =
2 atoms total
coefficient
subscripts

13. Day 4 Student Task:
Determine the type and number of atoms in 2CH4 and record on the table, page 4 of your foldable.
Answer: 2 carbon atoms and 8 hydrogen atoms.

14. Day 5 Notes (record on page 5 of foldable):
To determine if a chemical equation demonstrates the law of conservation of mass, calculate the number/type of atoms for both the reactants and products (coefficient x subscript)
Example:
2Na + MgF2 → 2NaF + Mg
Reactants
Products
Na = 2
Mg = 1
F = 2
Because there are the same number of each type of atom in the reactants and products, this equation is balanced and supports the law of conservation of mass.

15. Day 5 Student Task:
Student task: Determine if the equations below support the law of conservation of mass. Show your work on page 6 of your foldable.
Cl2 + KI → 2KCl + I2
4Na + O2 → 2Na2O
2Na + HCl → 2NaCl + H2
No; there is only one K atom in the reactants and 2 K atoms in the products. The I atoms are not balanced either.
Yes
No; there is only 1 H and Cl atom in the reactants and 2 H and Cl atoms in the products.

16. Day 6 Notes:
Record the following steps on page 7 of your foldable. Use these steps to balance the equation shown.
How to balance a chemical equation:
Determine type/number of atoms for reactants and products. (type is always the same for both)
Choose an element that is not balanced.
Add a coefficient in front of the formula with that element and adjust your counts.
Repeat steps 2-3 until balanced.