QOD #41

• Name one chemical PROPERTY and give an example of a chemical change that could happen because of that property.• Name one physical PROPERTY and give an

example of a physical change that could happen because of that property.

Law of Conservation of

Mass

The Law of Conservation of Mass - The mass stays the same before and after a physical change.

(Pizza Dough)

Making Lemonade – Proving Conservation of Mass

Materials: • Large clear cup• Dixie cup with lemonade mix• Water• Spoon• Mass scale

DON’T THROW AWAY ANY OF MY CUPS OR SPOONS.

Procedures:1. Fill up the cup with water ¾ full.2. Pour in the mix, but do not stir!3. Measure the mass of the cup of water mix and

record the mass.4. Mix the ingredients together and stir with

spoon. 5. Measure the mass of the ingredients after the

physical change.6. Drink lemonade!!7. Clean up, then answer questions.

Data Table:Mass Before Physical Change Mass After Physical Change

Total mass of cup of water + lemonade mix before stirring

_____________ grams

Total mass of cup of lemonade

after stirring _________ grams

Questions (RAP answers)

1. What happened to the mass before and after the physical change?

2. Why did that happen?

3. Why is dissolving a physical change?

Clean Up Procedures

1. Place small dixie cup back on tray where you found it.

2. Rinse out clear cup with water and place on tray in the front of the class.

3. Rinse off spoon with water and place in cup of spoons.

QOD #42

•Ms. Rathjen’s room is so cold that her bottle of water froze on her desk. If the mass of the water and bottle was 250 grams before the physical change, what was it after?

The Law of Conservation of Mass (in a chemical change) - The mass stays the same before and after a chemical change in a closed system.

Chemical Change– Proving Conservation of Mass

Materials: • Baking Soda• Water bottle• Balloon• Vinegar• Mass scale

DON’T THROW AWAY ANY MATERIALS! Be careful with balloons!

Procedures:1. Get a water bottle partially filled with vinegar.2. Put a spoonful of baking soda in the balloon with a

partner.3. Find the mass of the balloon with baking soda and the

bottle with vinegar before mixing them.4. Place the balloon over the mouth of the water bottle

and shake the balloon until all the baking soda falls into the vinegar. Hold the balloon onto the bottle!

5. After the chemical change has taken place, find the mass of the bottle and balloon (without removing the balloon from the bottle). Record data.

6. Write down qualitative observations and draw diagram.7. Clean up, then answer questions.

Data Table:

Mass Before Chemical Change

Mass After Chemical Change

Bottle of vinegar + balloon_____

Total mass of bottle with the balloon ______

Qualitative Data:

Diagram: (Label picture)

Questions (PQPA answers)

1. What happened to the mass before and after the chemical change? Why did that happen?

2. Why is it necessary to have a closed system for the Law of Conservation of Mass to apply to a chemical change?

3. Why was this reaction considered a chemical change?

The chemical equation for the overall reaction is:

NaHCO3(s) + CH3COOH(l) → CO2(g) + H2O(l) + Na+(aq) + CH3COO-(aq)

with s = solid, l = liquid, g = gas, aq = aqueous or in water solution

Another common way to write this reaction is:

NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2

10-5-12

QOD#20Tommy wants to see what happens to the mass of his milk as it sours in the refrigerator. The mass of the milk is 400 g before it goes bad.(Fill in the blanks below)1. The mass after the change is ______.2. I know this because _______.3. This is a ________ change because _______.