Science fairs give students an opportunity to delve into scientific concepts that excite them, and to be creative when planning their projects. Successful projects often begin with a hypothesis about the science behind something you see in your everyday life, and use innovative experiments to draw conclusions.

Some people freeze their chocolate bars before they eat them, but most people would not want to freeze their gummy worms first. The study of how different materials feel and behave is called materials science. Materials scientists have many jobs such as making sure buildings are able to last and withstand certain weather conditions.

This project uses simple materials science techniques to test the flexibility of candies. When you can bend a material and it holds the shape, it is “ductile.” A flexible candy bends on its own, while a brittle candy does not stay bent. Obtain six each of three types of candy. Unwrap three of each candy and place them in the freezer for one hour.

Unwrap the remaining candies. Take one in both hands, and bend it as slowly as possible, while watching closely to see what happens. Bend it until it breaks, or is folded completely in half if it will not break.

Rate each candy on a scale of 1 to 5. 1 is a very flexible, soft candy that bends on its own or does not hold its own shape when bent. 5 is a very brittle candy that does not stay bent, and if you bend it too far, it quickly snaps in half.

Repeat this for each of the three room-temperature pieces of all three candies. Do the same for the frozen candies, but do not remove them all from the freezer at once. Remove one, bend it and rate it, and then remove the next candy.

Calculate the average, or “mean value,” for each set of three candies in the freezer and each set of three candies at room temperature (see Resources for help calculating mean values). Compare the room temperature candies to the frozen ones, and the different candies to each other. Note whether certain candies were more flexible and brittle, and whether certain candies were more affected by being frozen. Consider what caused the differences in the candies.

Many people store disposable batteries in the refrigerator to keep them cool and dry. Others claim that household temperatures are cool enough for batteries, and that the presence of foods and condensation in a refrigerator will damage the batteries with moisture. This experiment tests whether there is any truth to the belief that batteries last longer in the refrigerator.

Obtain nine new, unused AA disposable alkaline batteries of the same brand. Store three of them in an airtight container in the refrigerator to protect them from possible moisture, and another three in a small open bin on the same refrigerator shelf as the other batteries. Store the remaining three inside a cabinet. Leave them there for one to three months.

At the end of the storage period, gather the batteries, taking care not to mix up the different groups. Wait about one hour to allow the refrigerated batteries to come to room temperature. You will need a battery voltage tester with a digital display, which you can purchase one for less than 10 dollars. Use the tester to measure and record the voltage number result for each battery.

Calculate the mean voltage for each group of batteries that were stored together (see Resources for help). Compare the average voltages of each group of batteries. The higher the voltage, the more life a battery has left. Did the results indicate whether being stored in the refrigerator extended the batteries’ life? Was there a difference between the two groups stored in the refrigerator?

The increasing number of children who are overweight often makes the news. Health authorities are concerned about overweight children’s risk of serious illness. Many organizations have launched initiatives to increase the fitness level of children who have a Body Mass Index (BMI) above the 85th percentile for their age. Unfortunately, there has not been a consensus about which, if any, strategies have been effective, or even whether children with high BMIs are less physically fit than their peers. This project explores the connection between children’s BMI and their cardiovascular fitness.

Develop a hypothesis predicting whether children with BMIs above the 85th percentile will have lower fitness levels than children with BMIs below the 85th percentile. Select a group of 15 to 20 boys and 15 to 20 girls. The children should all be within a two-year age range. Obtain consent forms signed by the children and their parents or guardians; your teacher should be able to help you create an appropriate form.

Measure each child’s height and weight. You can enter this data into the childhood BMI online calculator in the Resources section of this article to determine each child’s BMI. Measure their fitness using the Harvard Step Test. Testing one child at a time, ask each child to stand at the bottom of a staircase, and step up onto the first step with both feet and then back down to the floor with both feet, in an “up-up-down-down” rhythm. Have the child do this 30 times per minute for four minutes, or for less time if they become too exhausted to continue. Use a stopwatch, and count their steps out loud.

After the test, have the child immediately sit down. Measure their heart rate by feeling their wrist pulse and counting the heart beats for 30 seconds, then multiplying that number by two. Wait two minutes, and measure their heart rate again. For each child, subtract their heart rate two minutes after the end of the Harvard Step Test from their heart rate immediately after the test. The difference in the heart rates indicates how quickly their hearts are able to return to a resting rate after exertion. The larger the number, the higher the child’s fitness level.

Create line graphs comparing the children’s BMIs and recovery heart rate numbers. Consider your initial hypothesis and whether the results supported it. What conclusions can you draw about using BMI to measure fitness and health in children?