Day One
Get three plastic containers; they don't have to be very big, just enough to hold a handful of bean seeds. Lay some cotton wool in each container so each one is about half full. Put a handful of bean seeds on top of the cotton wool so they're evenly spread apart. Put water into the three containers; just enough so the cotton wool absorbs the water, but not so there's a pool of water on the bottom. Put two containers next to each other on a windowsill, or anyplace with plenty of daylight. Put the third container in a cupboard so the bean seeds don't get any light.
Day Two
Write headings on a sheet of paper: "Water and Light," "Light no Water" and "Dark." Underneath and to the left side of the headings, write "Day 2" then under that "Day 3" and under that "Day 4." You can continue the number of days later if you want to. Get your child to examine the three containers. The two in the daylight are identical and are starting to show signs of sprouting; the one on the cupboard doesn't show any signs of growth. Put a little water in one of the containers in the daylight, but not in the other container. Write down the results under the appropriate headings.
Day Three
Get your child to check the three containers again and to write down what he sees on the sheet of paper. The bean seeds in the container that was watered and in the daylight are shooting fast and small leaves are appearing. The bean seeds in the second container in the daylight have also grown, but the cotton wool is drying out, so the growth is not so pronounced. The bean seeds in the container in the cupboard show no signs of growth. Water the first container as before, but not the second container. Write down what is happening.
Day Four
Check the three containers again. The bean seeds in the cupboard are still not growing, although sometimes you may find very small shoots appearing, depending on how dark the cupboard is. The bean seeds in the container with water and daylight continued to grow and may be half an inch or so tall. The bean seeds in the third container have stopped growing and appear to be dying. The small shoots that originally appeared are beginning to shrivel. Write down what's happening to the bean seeds in each container.
Conclusion
You can continue the experiment for longer if you want, but four days is usually enough to show the effects that daylight and water have. Ask your child about the effects of water and daylight on the growth of the bean seeds and what is needed to grow healthy beans. Remember you can put the healthy beans into soil and watch them produce their own beans that you can eat. Put the container that was in the cupboard somewhere light and water it; the seeds will start growing within a day.