In general, it is not recommended to eat in a science laboratory, but there are some fun experiments that produce edible results. The key is to put away all chemicals, use clean glassware and work on clean surfaces. Here are several interesting experiments that result in edible products.
The Physics of Popcorn: Inside every corn kernel is a drop of water. When the kernels are heated the water turns to steam and expands, which causes the mini-explosion that creates the popcorn. Once the science is explained, the students can eat the popcorn.
Colored Celery: Celery stalks have xylem and phloem tubes in them which carry water and food from the roots to the leaves and back. This can be demonstrated by soaking the celery in water colored by edible food dyes. As the water travels up the xylem, the food dye is carried with it, turning first the stalks and then the leaves blue or red. The celery is still edible.
The Fizz: When carbonate bases are mixed with acid, the products are carbon dioxide gas, salt and water. This can be demonstrated by making 'sherbet'. Give your budding chemists some baking soda and citric acid crystals. Mix a quarter of a teaspoon of baking soda with a teaspoon of citric acid crystals and add tablespoon of icing sugar to the mix to make it taste better. As soon as a small amount is put on the tongue, the 'sherbet' starts fizzing as the carbon dioxide gas forms. The students should also taste the saltiness of the product as it dissolves.
Edible Cells: The typical cell is too small to see but is made up of organelles such as the cell membrane,cytoplasm, nucleus, ribosomes, mitochondria and a cell wall and green chloroplasts if it is a plant cell. Cells can be modelled using edible ingredients to give students a better concept of cell structure. Use jello or jam for the cytoplasm and licorice for the cell membrane. Green jello is perfect for a plant cell. Musk sticks make good cell walls. Then provide a number of different candies to represent the other cell organelles, such as tic tacs, jelly beans and M&Ms. Give your budding biologists pictures of cells to work from and let them choose how to make the cell. They can make a table that lists the names of the organelles, the functions of those organelles and the candies they used for their model. And of course when they finish, they get to eat their cell.
Marshmallow Genetics: In this experiment, junior biologists use toothpicks, marshmallows, tictacs and musk sticks or licorice and other candies to build an animal. The design of the animal is determined by the genes the students get. Make the genes out of paper strips: blue for the father and pink for the mother. There are genes for coat color (pink or white marshmallows), body size (1,2 or 3 marshmallows), neck length (short or long musk sticks), number of legs (4 or six), tail or no tail, number of eyes (2 or more). The students have to pull the genetic makeup of their offspring out of a hat, getting two genes, one from each parent, for each characteristic. There can be straight dominance rules (long neck dominant over short neck for instance) or there can be incomplete dominance (a white parent and a pink parent could make a pinto offspring). Once they have their genotype, the students then construct their animal. When they finish, they can eat it! This experiment creates some very strange beasts indeed. This is a very short introducion to this experiment. Check out the website http://www.practicalbiology.org/areas/advanced/genetics/modelling-inheritance/making-reebops-a-model-for-meiosis,77,EXP.html for more details on the method.
Chocolate Chip Geology: Valuable minerals seldom occur in a pure state. It is necessary to purify ores by removing the rock and worthless components and this can be simulated with chocolate chip cookies. The cookie is the ore. The choc chips are the gold. The students should weight their 'ore' first. Then they crush the cookie, taking care not to crush the choc chips. After crushing, the choc chips can be separated by sifting and sieving. The last of the 'dross' can be removed by adding a bit of water and floating off the lighter cookie crumbs. This is very similar to the industrial processes used to purify gold, iron, aluminium and other valuable minerals from their ores. The students can then weigh the choc chips to see what percentage of 'gold' occurred in their 'ore'. Save some whole cookies to be eaten at the end of the experiment.
Catsup Plate Tectonics: Although the ingredients of this experiment are edible, its pretty messy and I usually throw the results away. Spread the catsup or tomato paste on a board. This represents the molten magma that the tectonic plates float on. Use crackers to represent the plates themselves. They can be pushed around the catsup to simulate plate movements. When pushed together, the catsup wells up in the middle to show mountain building. When pulled apart the magma is exposed to show plate spreading. Plates can be slid alongside one another to show how the San Andreas fault is moving California. This is a lovely, messy experiment that will make plate movements much clearer.
Predator-Prey simulations: Predators are often specialised to catch specific types o prey. This can be simulated with various sorts of candies, nuts and pieces of fruit and vegetables. Give each student a plate of mixed foods and then give each one a particular tool with which to collect their food: tongs, toothpicks, forceps, nutcrackers, spoons and chopsticks are good tools to use. Then give each student one minute to forage. Afterwards, compare which tools were best for which sorts of foods. The toothpicks are great at picking up marshmallows but not so good for preying on tic tacs. It soon becomes quite clear that the kinds of food an animal can catch and eat will depend on what sorts of mouths, teeth and feet they have. When they are finished of course, the predators can be rewarded by eating their prey.
If your children think science is only for nerds, give them these experiments to try. They may change their minds.