Teachers.Net Lesson Plans

#109. Density of a Material

Science, level: Senior
Posted by Michael H. Edmondson (medmond@hotmail.com).
Hardaway High School, USA
Materials Required: Graduated cylinder (10 mL and 50 mL) Balance (triple beam) Stirring rod Weighing paper Teaspoon (plastic) Large plastic cup Small plastic cup Sodium borate solution (4%) Guar gum powder Food coloring (optional)
Activity Time: 1 class period
Concepts Taught: Density, chemical reactions

Laboratory - Density of a Material

Purposes:
(1) To determine the density of a material which is created
by «FirstName».
(2) To observe physical and chemical changes
(3) To observe chemical properties
(4) To observe physical properties
(5) To apply the method of weighing by difference.

Equipment and Materials:

Graduated cylinder (10 mL and 50 mL)
Balance (triple beam)
Stirring rod
Weighing paper
Teaspoon (plastic)
Large plastic cup
Small plastic cup

Sodium borate solution (4%)
Guar gum powder
Food coloring (optional)

Procedure:

After taking safety precautions (goggles and apron, gloves optional), mass the large plastic cup. Record the mass. Add five drops of food coloring (same color, different colors, none - but no more than five drops). Mass the cup plus food coloring. Record this mass. Add water to the third ring of the large plastic cup, using your graduated cylinder. Read the cylinder carefully. Record the volume. Determine the mass of the water, cup and (optional) food coloring. Determine the mass of the guar gum powder given to you. Record this mass.

Determine the mass of the small plastic cup. Fill this cup half full with sodium borate solution, using your graduated cylinder to determine the volume. Mass the cup plus the sodium borate solution. Record this mass.

Slowly dissolve the guar gum powder into the water/food coloring solution. Stir at all times. Add the powder slowly. Break up any "chunks" prior to adding to the water solution. This solution should change to a higher viscosity, but still be quite fluid.

When all of the guar has been dissolved, add at once the sodium borate solution. Immediately stir. Continue to stir, observing any changes which may be occurring. Stir for approximately 3 minutes.

Scrape as much material off the stirring rod back into the cup. Mass the

large cup plus the material. Record this.

DATA TABLES:

Before mixing the water/food coloring solution with the sodium borate solution:

(1) Mass of large plastic cup, water, and food coloring:_________________________

(2) Mass of large plastic cup plus food coloring:_______________________________

(3) Mass of large plastic cup:__________________________________________________

(4) Mass of weighing paper + guar gum:_______________________________________

(5) Mass of weighing paper:___________________________________________________

(6) Mass of guar gum:________________________________________________________

(7) Mass of sodium borate solution + cup:_____________________________________

(8) Mass of small plastic cup:_________________________________________________

(9) Mass of sodium borate solution:___________________________________________

(10) Volume of water:_________________________________________________________

(11) Volume of sodium borate solution:_______________________________________

(12) Volume of water/food coloring + sodium borate (add the previous two lines):
_______________________________

(13) Mass of water + guar gum + food coloring (if used) + sodium borate solution:

_______________________________

After mixing the water/food coloring solution with the sodium borate solution:

Divide the mass of the mixture (line 13) by the volume of the mixture (line 14) to determine the density of the material. Show the work here.

The density of my material is:_________________________________________________

QUESTIONS:

1. Discuss the changes which occurred as you stirred the guar gum into the water.

2. Discuss the changes which occurred after the sodium borate was added to the water/guar mixture.

3. What is density?___________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

4. What chemical changes did you see occur?_________________________________

______________________________________________________________________________

______________________________________________________________________________

5. Was there a chemical change involving the food coloring (did the solution remain the same color?)______________________________________________________

6. What is a mixture?________________________________________________________

7. Is the product a mixture?________________Why or why not?__________________

______________________________________________________________________________

______________________________________________________________________________

8. Explain the process of weighing by difference._______________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

9. What physical properties seem to have changed (if any)?____________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

10. What is guar gum normally used for?______________________________________

______________________________________________________________________________

______________________________________________________________________________