Is More Expensive More Absorbent?

Robert D. Wilson               Hermann Raster Elementary School
                               6936 S. Hermitage
                               Chicago IL 60636
                               (312)535-9144

Objective(s):

This lesson is geared to 4-6 grades but can be adapted to lower and upper 
grades.  Spill some water on your desk.  What is the first thing you grab?  A 
paper towel.  Students will find out through experimentation which paper towel 
is the most absorbent as well as which one is the best cost value for their 
money.  

Hypothesis:

The most expensive paper towel will be the absorbent and the best value for the
money.

Materials Needed:

class materials
4-6 different brands of paper towels     200 straws             1/2 lb. clay
30 clear plastic cups                    6 (mg) scales          6 (cm) rulers
6 (5 cm x 10 cm) cards                   6 pr. of scissors      water
300 clothes pins                         permanent markers      hole punch
6 styrofoam trays                        Stop watch 
                                            (or watch with second hand)
           
Strategies:


Part A. Which towel is most absorbent?

1. Tear off one sheet of paper towel from each of the four rolls.  
2. Fill your cup up half way with water.  
3. Use a marker and make a fill line half way up on the straw.
4. Put water into a straw by putting the straw in the water up to the fill line.  
5. Put a finger over the top of the straw and take the water out of the cup.  
6. Place water from straw on styrofoam tray.  
7. Place towel over the water on the tray.  (Do not press down on the towel, let 
   it absorb water on it's own.)  
8. Take towel off tray and measure the width of the wet spot.   
9. Repeat steps 1 through 8 for each brand of paper towels.  Remember to  
    completely dry the tray before continuing.  
10. Record the results of each to see which towel absorbed (had the largest wet 
    spot) the most water. 

Part B. How much water does each towel pick up?

1. Cut a 5cm x 10cm piece of paper towel.  Use the card as a template to cut the 
   paper towel to the right size.  Weigh it dry.  Record its weight.  (See 
   charts at the end).  
2. Weigh your cup.  Fill your cup up half way with water.  Weigh the cup with 
   water.  Record its weight.  
3. Fold the paper towel in half and wet it thoroughly.  
4. Skin off excess water over the lip of the cup.  Weigh the paper towel again 
   while wet.  Reweigh the cup and water also.  Record the results. 
5. Repeat this for each brand of paper towels. 

Part C. How fast does each towel pick up water?

1. Make a straw stand on your styrofoam tray to hang paper towels from.  Hang a 
   5cm x 10cm piece of paper towel (with 2 lines, 1cm and 2cm from the bottom) 
   using a clothespin from the straw across the top.  Use the clay to make the 
   straw stand is stationary and steady on the tray.  
2. Place the towel in the cup of water up to the 1cm line.  Time how long it 
   takes for the water to reach the 2cm line.  Record your results on the 
   charts.  Repeat this for each brand of paper towels. 

Part D. How strong is a wet paper towel?

1. Have one of your group members hold a 5cm x 10cm piece of paper towel by its  
top corners.  Wet the towel across the middle. 2. Add clothespins to the bottom 
of the paper towel evenly across the bottom.  Also add clothespins to the 
clothespins until the towel breaks.  3. Count the number of clothespins it took 
to break the towel.  Record your results on the charts.  Repeat for each brand 
of towels. 

Part E. How do paper towels compare in price?

1. Read the labels of each brand of paper towels.  Record the following data on 
the charts.
  a. The price of each roll.
  b. The square feet of each roll.
  c. The number of square feet you get for a penny.
        
   x = square feet = number of sq. ft. x    1 roll      
        penny            roll            price in pennies

  d. Calculate the milligrams of water absorbed for a penny.

   x =  mg   = square feet x 929cm2   x no. of mg absorbed
       penny      penny      sq. foot        50 cm2


Performance Assessment:

The students will be observed to see that they are active participants in the 
experimental process.  I will orally review with them the scientific process.
They will have to chart their progress and results of their findings.  I will 
also check their calculations when it comes to cost per usage to find the best 
value.  They will also be given a brief quiz over the materials presented.

Conclusions:

This lesson is meant to be fun and informative.  It crosses the curriculum by 
teaching Math: Computations and Concepts; Science: securing data from
experimentation, the Scientific Method process; Economics: finding the best
value for the money, cost effectiveness; Health: cleanliness; Reading: read
and understand product labels.

References:

Addison-Wesley Science textbooks