1. Conservation of Mass (or Matter)
11/3/14
Conservation of Mass (or Matter)

2. 1. Physical Change: Re-Shaping Clay
Mass Before Physical Change
Mass After Physical Change
Ball Shape: __________
Pancake Shape: __________
Ripped in Two: __________
Roll the piece of clay into a ball shape. Measure the mass. Record.
Flatten the clay into a pancake shape. Measure the mass. Record.
Return the clay to a ball shape. Measure the mass. Record.
Rip the piece of clay in two pieces. Place both pieces on the scale, measure the mass. Record.

3. Reflection:
What happened to the mass after the physical change? Why?
After the physical change, the mass stays the same because the amount of matter stays the same, only the shape changes.

4. The Law of Conservation of Mass (or Matter)
the mass stays the same during a physical change and a chemical change in a closed system
matter cannot be created or destroyed (disappear)
the number of atoms remain the same before and after the change

5. 2. Chemical Change: Vinegar & Baking Soda
Materials:
Water bottle w/vinegar
Balloon
Baking soda
Mass scale
Spoon
Goggles
(DON’T THROW ANY OF THE MATERIALS AWAY!)

6. Mass Before Chemical Change Mass After Chemical Change
Bottle of vinegar + balloon w/ baking soda ______
Total mass of bottle with the balloon attached ______
Qualitative Observations: Diagram: (draw a picture & label parts)

7. Procedures: Get a water bottle partially filled with vinegar.
Put the baking soda in the balloon. Someone will need to hold the balloon “open” while another pours the baking soda in the balloon.
Place the bottle of vinegar and the balloon with baking soda on the scale and record the mass.
Make sure everyone has goggles on.
Place the balloon over the mouth of the water bottle (make sure it is fully on the bottle) and shake the balloon until the baking soda falls into the vinegar.
After the chemical change has taken place, find the mass of the bottle and balloon (without removing the balloon from the bottle).
Make qualitative observations and draw diagram.
Place everything back on tray and return it to the counter.

8. After the chemical change, the mass decreased by about 2-3 grams because the gas that was produced (now in the balloon) isn’t accounted for on the scale. However, the same amount of matter is in the closed system, so the mass/matter is conserved. It is necessary to have a closed system during a chemical change to keep any gases produced from escaping.
Reflection:
What happened to the mass after the chemical change? Why?
Why is it necessary to have a closed system for the Law of Conservation of Mass to apply to a chemical change?