Páginas: 5 (1019 palabras) Publicado: 25 de enero de 2011
Chances are, you have several materials around your house made of gelatinized materials. Gels are used in all kinds of products and materials: pudding, diapers, insoles, packaging, ice cream, toothpaste, and many more. In this project, find out how gels are made and how they can be adjusted from firm to soft by changing the ingredients.
In this project you will make gelsout of cornstarch and water, and test if you can change the consistency of the final product by changing the ratio of ingredients.
A gel is a mixture of solid particles suspended in a liquid. The solid particles in the gel can absorb water, causing the gel to swell and increase in volume. If you have a baby brother or sister, you can see this in action by doing a quick experimentwith a diaper. Just dunk the diaper in a tub of water and watch it swell as it absorbs water. If you cut open the diaper you will see the pieces of gel that are absorbing the water. | | |
Not only are gels useful around the home, they have found many uses in science, medicine, and technology. Biogels are being studied that can be used in the body for repair or to deliver medicines. Aerogels havebeen used to collect star dust from a comet in space. Gels have even been designed to clean up radioactive contamination!
In this experiment, you will learn how to make a simple gel out of corn starch and water. You will vary the amount of corn starch in the gel from 5% to 20% to see if this will change the properties of the gel.
Terms, Concepts and Questions to Start Background Research
To dothis type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!
* gel
* gelatinization
* suspension
* mixture
* starch
* How are gels made and what are they made out of?
* How does gelatinization change the physical properties of a suspension?
*How does changing the ratio of ingredients change the consistency of the gel?

Materials and Equipment
* corn starch
* water
* measuring spoons and cups
* stir sticks
* small microwave-safe bowls
* permanent marker
* microwave oven
* cookie sheet lined with wax paper
* graph paper
Experimental Procedure
1. You will be making several suspensionsof corn starch in water, each at a different concentration. Each suspension will have a different percentage of cornstarch (5%, 10%, 15%, and 20%) suspended in water.
2. Label each bowl with the percentage of starch (5%, 10%, 15%, and 20%) using a permanent marker.
3. Mix the ingredients for each mixture following this table as a guideline:
| 5% | 10% | 15% | 20% |
cornstarch | 5mL (1 tsp) | 10 mL (2 tsp) | 15 mL (3 tsp) | 20 mL (4 tsp) |
water | 95 mL | 90 mL | 85 mL | 80 mL |
4. Safety note: As you heat the gel it can become super-heated and cause a burn. Take caution when stirring.
Heat each bowl separately in the microwave on high for a total of 1 minute 30 seconds by following these steps:
a. Stir each bowl thoroughly
b. heat for 30seconds
c. stir again
d. heat for 30 seconds
e. stir again
f. heat for 30 seconds
g. stir thoroughly

5. When you heat each suspension, make observations before and after heating. Does anything change? Write down your observations in a data table:
| Before Heating | After Heating | After Cooling | Number of Squares Covered |
5% | | | | |
10%| | | | |
15% | | | | |
20% | | | | |
6. Allow the suspensions to cool to room temperature before touching them, they will be VERY HOT! As they cool, do you notice any more changes?
7. When the suspensions have cooled to room temperature, touch them with your fingers. Write down your observations in a data table.
8. Now you will measure the thickness, or viscosity,...
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