Children are remarkable scientists. They learn about their world through constant experimentation, performing the same sequence of events until they can predict the outcome, and then changing something just to see what will happen. Their natural curiosity makes most elementary school children approach science class enthusiastically, but too often that enthusiasm is sapped by tedious lists of terms taught by teachers who are more than a little apprehensive of the subject. Even if class time is devoted to hands-on projects, the experiments are generally spelled out for the students and require little thinking or creativity.
If you home-school your children, creative, child-driven experiments can be an integral part of their science curriculum. If your children are in a school that teaches science mainly through memorization of facts, experimenting on the weekends will help them better understand the importance of the concepts they are learning and keep them excited about the subject.
When helping your child design and perform an experiment, there are some important concepts that should be considered. First, an experiment should help answer a question. This could be as simple as “what happens if I add blue food coloring to the water?” or as complex as “how many genes are involved in rose color?” It is best if the question is one that your child asks, perhaps in response to a previous experiment.
Second, try to test only one variable per experiment. If your child is interested in how temperature and moisture affect radish growth, help her design an experiment to test each. If you try to change both at the same time, it will be difficult to determine how much of the results are caused by a difference in moisture and how much from a difference in temperature.
Finally, the most important consideration is to choose an experiment which interests your child and which your child can perform most, if not all, of and understand the results. Even if the initial experiment design comes from some other source, if the child does the work and takes the data, it becomes her research.
With those principles of in mind, here are two well-designed experiments to practice with and to stimulate your child’s scientific imagination.
1. What location is more biodiverse: the kitchen or the bathroom?
2 baking dishes of the same size
1 package instant gelatin dessert (any flavor)
Plastic wrap or lids for the baking dishes
Sterilized water (boil water for 20 minutes, allow to cool to room temperature)
Plant mister (or clean hair spray bottle)
1) Sterilize the baking dishes and their lids by boiling them or washing in the dishwasher.
2) Prepare the instant gelatin dessert mix according to the directions on the package. While the mixture is still hot, pour a centimeter thick layer in each dish. Cover with the lids or with plastic wrap and chill until the gelatin has set.
3) Put a dish in safe places in the kitchen and the bathroom. Remove the lids.
4) Check the dishes daily. If the gelatin starts drying up, mist very lightly with sterilized water.
5) Once colonies are visible, count the number of total number of colonies and of different looking ones on each plate and compare. Research biodiversity and decide, using data from the experiment, which room is more biodiverse.
This experiment can be repeated testing different room’s biodiversity, how moisture affects fungal growth or which gelatin flavors are best for catching organisms
A fungal garden is easy to construct using the colonies collected from this experiment. Just prepare another baking dish as in steps one and two. Carefully cut a small piece (about 1 cm x 1 cm) from the outer edge of each colony you wish to transplant. Lay this piece on the new dish. Be sure to use a different, sterilized knife for each colony to avoid contamination and always wash hands after working with the organisms.
2. How many pieces of candy are in the bag (mark-recapture technique)?
A paper bag
Wrapped hard candies
A permanent marker
1) Decide you many pieces of candy you want to sample, depending on haw much time and effort you want to devote to this experiment, we’ll call this number A.
2) Draw out A pieces of candy. Mark each one with the marker and return them all to the bag at the same time.
3) Mix the bag of candy well and pull out A pieces of candy again. Record how many are marked. We’ll call the number of marked ones M.
4) Now estimate the total number of candies in the bag using this relationship:
M/A = A/Total
Once your child learns the mark-recapture technique, the experiments she can design are endless. She can actually count the number of candies present to learn how the size of the sample affects the accuracy of the estimate and record data to determine how many candies of each color are in the bag. Once the candy bag possibilities have been exhausted, sampling can be used to estimate how many people are in a store (What day is more popular for shopping, Tuesday or Thursday?), at a function (How many children attended? How many were from out of state?). After carefully researching trapping and marking techniques, she can also estimate wildlife population sizes.
After a few experiments, it becomes practical to keep records – what was asked, how the experiment was performed, what was found. A notebook kept exclusively for his research will keep the scientist organized and serve as a record of his growth. For home schooled students in states that require a portfolio, this lab book will be an invaluable addition.
As your child becomes a more experienced researcher, he or she will naturally develop more elaborate experiments. Poorly designed experiments, however, only yield uncertain results and reinforce bad scientific procedure. The two biggest design flaws to be on the lookout for are nonrandom sampling and inconsistent measuring.
Suppose your child decides to see if distance from the highway affects tree growth. She suspects that it does, believing that the tress nearest the road will be the smallest. She decides to measure the diameters of five trees in three different areas. Sure enough, the further from the road, the wider the tree.
Because she already had an idea how the experiment would turn out, the young scientist may have subconsciously chose thin trees at one location, wide ones at another. In order to prevent this unintentional nonrandom sample – which plagues even experienced researchers – it is important to have a randomization scheme. You could, for example, take a couple of dice and a tape measurer with you to the field. Before every measurement, pick a direction, roll the dice, and move the number of feet you rolled in the direction you chose. The tree closest to you is randomly chosen.
Nonrandom sampling can easily occur when measuring animal populations. Imagine your son wants to estimate the number of squirrels in the woods using the mark-recapture technique. You help him devise a very humane trap that lures squirrels with peanuts and lets you mark them with a spot of flour.
A squirrel will quickly learn what your trap looks like and that it means a free treat. Over the course of the day, you may recapture the same squirrels several times, which will cause you to underestimate the number of squirrels in the area.
Conversely, if you hurt the squirrel in any way, he will avoid the trap in the future and you may overestimate the population.
Even the data obtained from a completely random sample can be skewed if the experimenter takes inconsistent measurements. Once at a family gathering, two of my cousins were comparing their hat sizes. The mother of one, eager to show that everyone had more or less the same size head, measured her son’s head. Holding the tape measurer to mark the right place, she “measured” the head of each person in the room.
Sure enough, everyone had the exact same size head. She was convinced, even after several people pointed out that she had measured some heads right at the brow, some only an inch or two from the top. Finally, the two cousins exchanged hats, but even the sight of a tiny hat perched on an extra-large head next to a head swallowed by an enormous cap did not persuade the former teacher that something was wrong with her experiment.
Consistent measurements are key to having valid projects, and usually not much extra work is involved. Trees can be measured consistently at shoulder level, heads right at the brow.
By giving her the opportunity to design and perform meaningful, interesting experiments you will nurture problem solving skills, patience and your child’s self-esteem.
With encouragement and support, her scientific curiosity and knowledge can continuously grow.