lab investigation: law of conservation of mass matter cannot be created or destroyed - it can only...

LAB INVESTIGATION: Law of

Conservation of Mass

Matter cannot be created or destroyed - it can only

be changed!

MATERIALS:• graduated cylinder • beaker• small plastic canister• 30 mL of water (H2O)• 2 g of baking soda (NaHCO3) • 4 g of calcium chloride (CaCl2) • Ziploc plastic bag • safety goggles• triple beam balance• 2 spoons each with a LABEL – baking soda

and calcium chloride

PROCEDURE & DATA:1. Be sure to wear safety goggles when

doing this investigation!

PART I:Baking Soda

& Water

2. Use the graduated cylinder to add 15 ml of water to the beaker.

3. Add 2 grams (about ½ teaspoon) of baking soda to the water in the beaker. Only use the spoon for dry baking soda

Swirl gently until most of the baking soda dissolves.

PART II:Calcium Chloride

& Water

4. Add 4 grams (about 1 teaspoon) of calcium chloride to the plastic bag. Use the spoon for dry CaCl2

5. Use the graduated cylinder to add 15 ml of water to the plastic bag. Seal the bag and gently swirl it until most of the calcium chloride dissolves.

What do you observe about the contents of the bag?_________________________

CAUTION: If there is a leak or spill, inform your teacher.

Wash your hands if the chemicals come in contact with your skin.

The product is acidic and can irritate your skin!

PART III: All-in-One Bag!

Baking Soda Solution &

Hydrochloric Acid

6. Pour the liquid from the beaker of baking soda solution into the small canister. Do not pour in any of the undissolved baking soda! Liquid only!

7. Place the sealed plastic bag and the plastic cup on the triple beam balance and record their total mass.

Total Mass of the System BEFORE the Final Reaction: ____________g

8. Carefully stand the cup of baking soda solution inside the bag. Without spilling the contents of the container, squeeze the air out of the bag and seal it.

9. Without opening the bag, tip over the cup allowing the two liquids to mix. What do you observe about the contents of the bag?

__________________________________________________________ _____________________________

10. After it stops releasing gas, place the bag on the balance and measure the mass of the system again. Record this as the final mass after the reaction.

Note: Measure the mass of the system quickly. Plastic bags may have small leaks around the sealing strip.

Total Mass of the System AFTER the Reaction: ____________g (Final Mass)

11. Determine how much gas was produced by slowly unsealing the bag. Once the gas has left the bag, reseal it and determine the remaining mass.

12.Subtract the new mass from the final mass to calculate the mass of the gas produced.

Mass of the Gas Produced: ____________g

Clean-Up & DisposalFollow posted clean-up & disposal procedures: Plastic bags are to be emptied into the sink & then

thrown away in the trash can.

Canisters are to be cleaned in the sink & returned to the lab table.

Goggles are to be wiped with alcohol (not lenses – only areas that contact skin or hair) and kept at the lab table. Throw away used alcohol swabs.

Any spills, breakage, injuries, or accidents MUST be reported to the teacher immediately – no matter how small or unimportant they may seem!

Big Ideas to Discuss:

Evidence of a Chemical Change! When a chemical change occurs, the chemical ______________ of the substances are changed. Atoms are _______________! Was Any Mass Lost? Possible Sources of Error in Investigation… Law of Conservation of Mass! What do the products likely taste like? …and why SHOULDN’T you taste them?