1. Alka Seltzer and density

2. Density of Gas
Lab

3. Chem Catalyst
You have seen the commercials, maybe used the product yourself.
What is happening when the tablet begins to fizz?
Does all of the tablet’s initial matter remain in the water? Explain your answer.
If not, where does it go?

4. In your comp book…
Write down the title and goal of the gas density lab.
Write down the procedure required to obtain the volume of gas released from ½ an antacid tablet.
Write down the procedure required to obtain the mass of the gas released from ½ an antacid tablet.

5. Goals
Develop a simple method that allows for capturing the gas released from a chemical reaction
Determine the density of the released gas
Determine why gas generally moves up and out of a beaker
Determine is a chemical reaction has taken place

6. Main ideas All matter has density, even if the matter can not be seen
The density of gas is much less than the density of solids and liquids
The pressure of the trapped gas on the liquid is greater that external air pressure.

7. To find the density of anything, what information do you need?

8. Answer:
The mass and volume of the object

9. Materials needed 100 ml graduated cylinder
600 ml griffin beaker, 100ml beaker
Water
2 antacid tablets (keep these dry until use!)
Piece of aluminum foil
Good eyesight and quick reflexes

10. To Find the volume of gas
From Antacid tablet

11. Procedure to determine the volume of gas
Fill up a graduated cylinder to the very top with warm water (record temperature)
Fill a 400 ml ml beaker about ½ full of warm water
Cover the top of the cylinder with a piece of aluminum foil
Quickly invert the cylinder an place into the beaker
Remove the aluminum foil
Break an antacid tablet in half

12. Procedure, part 2
g. Drop ½ of the antacid tablet into the beaker, quickly cover the tablet with the inverted graduated cylinder h. As antacid dissolves the level of water in cylinder should go down i. Make sure all pieces of antacid dissolve under the cylinder j. Repeat procedure with other ½ of tablet. k. Clean up area, wash beaker and cylinder

13. Volume chart Antacid Tablet section Volume of gas (include units)
Temperature of water (⁰C)
1st Piece
2nd Piece

14. To find the mass of gas from an antacid tablet

15. Procedure to determine the mass of gas locked in a antacid tablet
Take a small beaker (100 ml) and fill it with 40 ml of warm water
Find the mass of beaker with water and a tablet of antacid, DO NOT put tablet into water during the weigh in
Add 1 tablet of antacid to water , let tablet dissolve completely
Find the mass of beaker and water after tablet dissolved
Clean and dry beaker

16. Chart for mass of gas before tablet was placed into beaker
Description of objects to be measured
Mass value (g)
Mass of all (beaker, water, tablet)
before tablet was placed into beaker
Mass of all (beaker, water,)
after tablet dissolved
Mass of the gas: The difference between the above measures
Temperature of the water
value in degrees celsius:

17. Calculate density of gas
Determine the density of gas :
__________________ g/ml
__________________ g/cm3

18. List of ingredients of Alka Seltzer
A lot of Baking Powder (BiCarbonate of Soda)
A tiny amount of Aspirin
A small amount of Citric Acid for flavor
What material(s) do you think composes the gas? (Hint: Think of what you exhale with every breath)