Solutions and Materials
At times, you may wish to make your own materials rather than purchase them. This section tells how to make certain materials. The quantities listed below are recommended for a class of 30 children working in 6 groups.
Children can use adobe bricks to build various types of structures and models.
- The children can make their own adobe bricks from loam and straw.
- Mix about 4 cups of loam with small pieces of straw.
- Add enough water to make a thick mud.
- Place the mud in hollow blocks, ice-cube trays, or any cube-shaped containers.
- Place the cubes in a very warm place for about 2 weeks.
- Remove the cubes from their containers.
Alum can be used to study crystal growth and to investigate the properties ofsaturated and supersaturated solutions.
- Alum can be obtained from a drugstore.
- To grow large alum crystals, the children need a saturated solution of alum.
- To prepare this solution, place 250 mL (1 cup) of water in a pan.
- Add 6 teaspoons of alum to the pan.
- Heat but do not boil the solution.
- Remove the pan from the heat.
- Stir in 1 teaspoon of alum at a time until no more will dissolve.
- When this solution cools, pour it into small plastic jars. Have the children suspend their seed crystals in the jars.
Baking Soda Solution
Baking soda solution can be used to produce carbon dioxide, by addition of an acid.
- Place 1 L (1 quart) of water in a plastic jar. Stir in baking soda one spoonful at a time until no more will dissolve.
- Pour off the clear liquid. Store in dropper bottles.
Beet Juice Indicator
Beet juice is an indicator, a substance that changes color as the pH of a solution changes. Beet juice is red in acidic solutions and blue in basic solutions.
- Wash and slice a fresh beet. Place about four slices of beet into a pan containing 1 cup of water.
- Heat until boiling and continue heating for about 5 minutes.
- Remove the beet slices and allow the red liquid to cool.
- Store in dropper bottles.
Bromothymol Blue (BTB)
Bromothymol blue is an indicator, a substance that changes color as the pH of a solution changes. Bromothymol blue is yellow in acidic solutions and blue in basic solutions.
- BTB can be prepared by mixing 0.1 g (a pinch) of bromothymol blue powder in 10 mL of a 4% solution of sodium hydroxide.
- Add 20 mL of alcohol and dilute to 1 L with distilled water.
- The solution should be deep blue.
- If it is green, add sodium hydroxide solution drop by drop until the solution turns blue.
- Bromothymol blue can be purchased from scientific supply houses.
CAUTION: Sodium hydroxide is corrosive; the BTB solution should be prepared in a laboratory. BTB stains hands and clothes. Have children wear goggles and follow safety precautions when using BTB solution.
Bubbles can be used to investigate a variety of phenomena, including motion, surface tension, and refraction of light.
- To prepare a bubble solution that yields giant, long-lasting bubbles, add 1 cup liquid detergent and 2½ teaspoons glycerin to 3 cups water.
- Stir this mixture carefully so that an excessive amount of suds does not form.
CAUTION: Have the children wear safety goggles when blowing soap bubbles.
The growth of crystals can be observed by making a crystal garden.
- Half fill a clear plastic jar with hot water.
- Slowly add salt to the water and stir to dissolve.
- Continue adding salt until no more will dissolve.
- Place 1 tablespoon of vinegar in the water.
- Place a piece of charcoal or small porous stone in the jar.
- Beautiful crystals will soon start to form on the charcoal or stone.
Daffy dough will fascinate the children with its unusual properties. It is fun to make and examine.
- Each group of children should stir ½ teaspoon of salt into ½ cup of liquid starch in a medium-sized container.
- Add to this ¼ cup of white glue.
- Stir for 5 minutes.
- As this material starts to coalesce, have the children knead it until it forms a ball.
- Squeeze out the excess liquid.
- If the mixture does not coalesce, add salt sparingly and continue to knead the dough.
Dough can be used to prepare and study imprints.
- To prepare dough, combine 10 cups of flour, 2½ cups of salt, and 4½ cups of water.
- Mix thoroughly and knead to remove any lumps. Make six dough balls, wrap each in plastic, and store them in an airtight container.
Gelatin is a colloid and can be used to investigate the properties of this type of mixture. Gelatin can also be used to simulate the ground movement that occurs in certain types of soil during an earthquake.
- Prepare gelatin by mixing the powder with hot water.
- Stir until the powder dissolves. Pour the solution into a clear, plastic bowl and place the bowl in a freezer overnight.
Goo is a mixture that can be used to investigate the properties of matter in the liquid and solid states.
- To make goo, put ½ cup of water into a cup and add 5 drops of food coloring.
- Sprinkle 2 packages of plain gelatin on the colored water. Let this sit for one minute. Then stir the mixture for one minute to break up the lumps.
- Let the mixture sit for three hours so that it gels slightly.
Hard water is water that contains large amounts of dissolved minerals. It can be used to investigate how dissolved minerals affect the taste of water and the cleansing action of detergents.
- To prepare hard water, first crush four antacid tablets that contain calcium carbonate as an ingredient.
- Be sure the tablets are crushed to a powder. Then mix the powder with 200 mL of water.
Indophenol Blue Indicator
Indophenol blue is used to test for the presence of vitamin C, changing from blue to colorless in the presence of the vitamin.
- Prepare this vitamin C indicator by mixing 0.1 g of indophenol blue powder in 1 L (1 quart) of distilled water.
CAUTION:Have the children wear safety goggles when using indophenol blue.
Iodine indicator is used to test for the presence of starch. It turns blue-black when starch is present.
- Iodine indicator can be purchased from scientific supply houses as Lugol's solution.
- Lugol's solution can be prepared by dissolving 10 g of potassium iodide in 100 mL of distilled water.
- Then add 5 g of iodine crystals and mix. (Use caution handling these chemicals; the solution should be prepared in a laboratory.)
- Store the solution in brown dropper bottles. Tincture of iodine obtained from a drugstore may also be used as an indicator.
CAUTION: Iodine stains hands and clothes and is toxic. Have children wear goggles and follow safety precautions when using iodine indicator.
Iron filings can be used to investigate chemical change (rusting), including the observation that a component in air (oxygen) is involved in the process.
- Iron filings can be made from a dry, fine-grade (grade 0000) steel wool pad, the kind without soap.
- Put on gloves.
- Pull the steel wool pad into two halves, hold them over a piece of paper, and rub them together so that the iron filings fall onto the paper.
- Carefully pour the iron filings into a dry jar.
- Cover until ready to use.
Limewater is used to detect the presence of carbon dioxide, becoming milky-cloudy when carbon dioxide dissolves in it.
- Add about 3 g of calcium hydroxide to 1 L (1 quart) of warm water in a plastic bottle.
- Cover and shake well. Let the solution cool.
- Pour off the clear liquid.
- Store in a plastic bottle until ready to use.
CAUTION: Have the children wear safety goggles when using Limewater. Do not ingest limewater.
Modeling dough can be used by children to make small models and structures. It can also be used to investigate the properties of matter.
- To prepare modeling dough, mix 1½ cups of salt, 3 cups of flour, and 2 tablespoons of cream of tartar in a large bowl.
- Add ¼ cup of vegetable oil. Mix a few drops of food coloring in 2¾ cups of boiling water and add this to the mixture.
- Mix until the color is uniform.
- Store dough in an airtight container.
Artificial ocean water can be used to investigate the physical and chemical properties of seawater.
- To prepare artificial ocean water, dissolve 300 g of table salt, 42 g of magnesium chloride, 28 g of magnesium sulfate (Epsom salts), and 14 g of plaster of Paris in 11 L of water.
Phenolphthalein is an indicator, a substance that changes color as the pH of a solution changes. Phenolphthalein is purple in very basic solutions and colorless in slightly basic and in acidic solutions.
- Ask a pharmacist at a drug store for a package of any laxative that contains phenolphthalein.
- Use the back of a spoon to mash four tablets on a saucer.
- Pour this powder into a small cup; add about 10 mL of rubbing alcohol.
- Let this mixture soak for about 15 minutes.
- Pour off the liquid and store in a dropper bottle.
Children can investigate polymerization and the properties of a polymer with an example they prepare themselves. Prepare the following solutions ahead of time.
- Solution A: Place about 1 L (1 quart) of water in a pan.
- Slowly sprinkle 40 g of poly (vinyl) alcohol on the water, while stirring.
- Heat this mixture (on a hot plate) to about 90°C.
- Do not boil it.
- Stir this mixture for about 20 minutes, until it looks like white corn syrup.
- Cool and store in a plastic jar.
- Solution B: Dissolve 8 g of borax in about 200 mL of water.
- Stir until dissolved.
- Store in a plastic jar.
- To prepare the polymer, have the children place 30 mL of solution A in a paper cup.
- Add to this 10 mL of solution B.
- Stir with an ice-cream stick until a soft ball is formed.
- Remove the polymer ball from the cup and knead for about 5 minutes.
Red Cabbage Juice Indicator
Red cabbage juice is an indicator, a substance that changes color as the pH of a solution changes. Red cabbage juice is red in acidic solutions, and green or blue in basic solutions.
- To prepare red cabbage juice indicator, tear about five leaves of red cabbage into small pieces.
- Place these in a large beaker or a stainless steel pot.
- Add 1 L of water, bring to a boil, and simmer until the water turns a deep purple.
- Pour the liquid through a strainer or through a piece of cheesecloth into a storage bottle. Keep the solution refrigerated.
A salt/sand/iron-filings mixture can be used to investigate the nature of mixtures and to allow children to experiment with methods of separating a mixture.
- Add the following materials to a large plastic jar with lid: 1 cup kosher salt, 1 cup sand, and ¼ cup iron filings.
- Shake to mix well.
- Each group of children will require about ¼ cup of this mixture.
Salt solution can be used to investigate the properties of solutions, including means of separating the components.
- To prepare a 2% salt solution, dissolve 2 g of table salt (sodium chloride) in 98 mL of water (preferably distilled).
Simulated Solid Waste Bag
Simulated solid waste is useful for having children determine the kinds of materials that are disposed of by people, and for investigating recycling possibilities.
- Gather a collection of items representative of the materials typically found in solid waste.
- You could include the following: toothpicks, plastic pieces cut from canned soda cartons, paper clips, metal soda tabs, paper, cardboard pieces, glass droppers, metal and plastic jar lids, and rubber bands.
- Each group of children will require one bag of solid waste.
Children can investigate the unusual physical properties of Super Starch.
- The following recipe makes enough Super Starch for six groups of children.
- Mix 4 boxes of cornstarch with 6¾ cups of water. Add 15 drops of food coloring if desired.
- Store in an airtight container until ready to use.
- For easy clean up, let the material dry and wipe up with a moist cloth.
Yeast culture can be used to observe reproduction by budding. Yeast culture can also be used to investigate fermentation and production of carbon dioxide.
- Prepare yeast culture, using a packet of dried yeast and following the directions on the label. or
- Add about 25 mL of molasses or grape juice to 450 mL of water.
- Then add ½ package of dried yeast to the mixture and mix.
- Set aside in a warm place.
- The culture will be ready to use the following day.