# 2.5-2.6

## 2.5 The Mass of Copper and Sulfur

Purpose: To determine if the total mass of sulfur and copper increases, decreases, or stays the same when they are heated together.

Procedure:

1. Clean pan and zero balance
2. Find mass of test tube, sheet, and band together
3. Add 2 grams to balance
4. Measure 2 grams of copper until balanced
5. Add copper to test tube
6. Mass piece of paper towel
7. Add 1 gram to balance
8. Add sulfur to paper towel until balanced
9. Add sulfur to test tube
10. Cover top with rubber sheet and wrap rubber band around tube to secure
11. Record mass of test tube, sheet, band, sulfur, and copper unheated
12. Have Mr. Leeds check setup
13. Light burner, heat mixture, and observe
14. When reaction ends, cap flame
15. Find mass of heated test tube, sheet, band, sulfur, and copper
16. Clean up
Materials:

• Balance
• Paper towel
• Large test tube
• Rubber sheet
• Rubber band
• Sulfur
• Copper
• Burner
• Matches
• Large clamp
• Pegboard
Post Lab:

• Melting point of copper is 1100 C (2000 F)
• Melting point of sulfur is 112 C (235 F)

Yellow Smoke:

• Water in sulfur turns to vapor (gas) and rises in test tube
• When it cools, sulfur bonds with copper, forms copper sulphide
Experimental Errors:

• Hole in rubber sheet, gas could escape, decrease in mass
• Sheet pops off, gas could escape, decrease in mass
• Rubber band pops off, gas could escape, decrease in mass
• Not sealed around top of test tube, gas could escape, decrease in mass
• Sulfur sticks to sides of test tube, doesn't react with heat

## 2.6 The Mass of a Gas Lab

Purpose: To determine if the mass will increase, decrease, or stay the same when a solid and liquid produce a gas.

Procedure:

1. Clean and zero balance
2. Fill bottle 1/3 with water
3. Mass bottle, cap, and tablet in cap (dry cap)
4. Put tablet in bottle (don't touch with hands)
5. Wait 30 seconds and mass bottle
6. Slowly loosen cap (DON'T REMOVE)
7. Mass bottle

Materials:

• Alka-Seltzer tablet
• Bottle
• Water
• Balance
• Cap

Lab Safety: -Wear goggles

Experimental Errors:

• Water in pan during Mi, lose mass
• Cap is wet during Mi, lose mass
• Touch tablet after Mi, lose mass
• Cap is not tight or on quickly enough, lose mass
Alka-seltzer:

• Antacid (suppresses acid) and pain reliever
• 3 ingredients: aspirin, citric acid, and sodium bicarbonate (which produces a gas)

## 2.7 The Conservation of Mass

Closed System: A space where nothing can enter or leave

Groups that had no change in mass (including sensitivity of the balance):

• 2.1: 75%
• 2.4: 75%
• 2.5: 50%
• 2.6: 48%
Law of Conservation of Mass: In a closed system, mass will remain constant, regardless of the actions of the processes inside the closed system.