Your kitchen makes a great laboratory! Learn about chemistry and biology topics as you explore there. And if you're looking for a science fair project idea, your kitchen is a great place to start. Most of these projects take about a week before you see any results.
Dissolve an Eggshell
Make an egg shell disappear without touching it! Set a raw egg in a glass of white vinegar (acetic acid), so that it's completely covered in the liquid. Bubbles should start to form on the surface of the egg almost immediately. Let it sit for a week and then carefully take the egg out. What happened? The acid 'ate' away and dissolved the calcium carbonate that the shell is made out of! There might be some chalky white residue left on the egg that you can gently scrape off. The inside of the egg is still intact, though, because vinegar doesn't break down the egg membrane. The egg also swells up, because some of the liquid seeps inside it. You should be able to see the yellow yolk through the membrane. How does the shell-less egg feel? Pick it up carefully to avoid popping it.
You can also try the experiment with a peeled boiled egg (boil it for 10 minutes). What do you expect to happen? The vinegar actually doesn't eat up the egg, but makes it feel somewhat rubbery. You can also try this with chicken bones. After a week in vinegar, the bones will be rubbery, because they lost calcium and other hardening minerals.
Make Sugar & Epsom Salt Crystals
Use sugar and water to grow edible crystals! The sugar and water should be mixed in a 2:1 ratio, such as 1-1/2 cups of sugar and 3/4 cups of water. This works best with a small saucepan on the stove, although you can use a microwave instead.
1. Heat the water to boiling and then add the sugar, stirring until no more can be dissolved. (The solution is saturated.)
2. Continue to heat the solution until it is clear. Pour the solution into a glass, but go slowly so you don't get any undissolved sugar from the bottom of the pan in the glass.
3. Next, dip a clean piece of cotton string into the solution so that the lower part of the string is coated. Take the string out and let it dry, then suspend it in the solution, part in and part out, for a week. (You might tie one end to a pencil and set the pencil over the mouth of the glass.)
Once a saturated solution starts to cool, the loose solute (sugar, in this case) molecules start to join with the solute molecules on the string, while the solvent (water) molecules get closer together, losing more solute. The solute crystal gradually develops around the group of solute molecules on the string.
Epsom salt crystals are even easier to grow:
(Note: Unlike sugar crystals, the Epsom crystals are not edible.)
1. Fill two 6-8 ounce cups with warm water and stir Epsom salt into each until no more salt will dissolve. Tie a washer or other small weight to each end of a 12' piece of cotton string.
2. Set each end of the string in one of the cups, with the middle of the string hanging down loosely into a 'u' shape. Set a plate underneath to catch the drips as the water and salt solution moves along to the middle of the string.
After a few days, you should see tiny crystals forming along the string. The air causes any leftover water to evaporate, leaving a solid crystal. After a week you can take the string out of the water and examine the crystals more carefully. You can also try this activity with table salt.
There might be a white buildup on the crystals from the minerals in the water or mixed with the salt. Try rubbing it off so you can see the clear crystals. If you can, use distilled water to avoid some of this mineral buildup.
If you have a microscope or magnifying glass, compare the sugar and Epsom salt crystals to each other to see if they have a similar crystal structure. You can also compare the crystals to a few grains of sugar and of Epsom salt.
Homemade Ice Cream & Butter
After hundreds of years, the best ice creams are still made with fairly simple ingredients: milk, cream, sugar, and maybe eggs. You can make ice cream using simple ingredients!
What You Need:
- 1/2 cup milk
- 1/2 cup cream
- 1/4 cup sugar
- 1/2 teaspoon of vanilla or other flavoring
- Quart-size ziplock bag
- Gallon-size ziplock bag
- Rock salt
What You Do:
1. Stir the milk, cream, sugar and flavoring together in a bowl, then pour the mixture into a quart-size freezer ziplock bag.
2. Stick this bag inside a gallon-size ziplock, half-filled with ice and rock salt - about 2 cups of ice and 1/2 cup of salt. Salt lowers the freezing point of water, which causes the ice to melt at a lower temperature. The lower freezing point provides the temperature difference needed to transfer heat between the freezing ice cream ingredients and the melting ice. Use a thermometer to measure the temperature in the outer bag. Next, begin shaking the bag so that the ingredients are whipped together.
3. What do you expect to happen to the cream mixture? After five minutes of shaking, let the bag sit for a few minutes. Now take the temperature inside the gallon bag again. Has it changed? What happens if you don't shake it?
Ice cream is a colloid, an emulsion where two substances are just suspended within each other rather than being chemically bonded together. This is why many ice creams also have an emulsifier to prevent the fat molecules from separating from the rest of the ice cream (this makes the texture of the ice cream smoother). Ice cream also uses a stabilizer (like gelatin or guar gum) to help hold air into the ice cream, which gives it its light texture. To be officially called ice cream, the colloid has to be at least 10% milk fat and 6% non-fat milk solids (such as proteins).
Butter is made in a similar way. Pour some heavy cream into a small jar, screw the lid on tightly, and shake the jar briskly for 10-20 minutes. The butterfat molecules in the cream collide as you shake the jar, and they begin to stick together, forming butter and leaving the watery liquid of the cream separate. You'll notice a change in how the sloshing sounds and how heavy it feels. (Regular milk has a lower fat content than cream. Can you still make butter using whole milk? Skim milk has had so much fat removed that it can't be used for butter.)