Aim The aim of this experiment is to encourage children to devise an experiment in order to answer a science question. Young children have a tendency to rely on adults as the source of all knowledge and will usually answer a question of “how do you know?” with “because my daddy told me”. This question “Do seeds need water to grow?” is a simple one with a straightforward yes or no answer that can investigated experimentally by children who are very young.

Age range This lesson is designed for children aged around 6 to 7 years old. For younger children the lesson could be modified by focussing less on fair testing and concentrating on simply finding out the answer. For older children or more able children the question could be extended to include “How much water is optimum”

Lesson Starter Dear Gardener's Questions I am trying to grow some yummy cress seeds to put in my egg sandwiches but they will not grow. I know that I need to plant them in some soil but what else do they need? Ever hopeful Teresa Green Show children a letter from a concerned gardener. Tell them that they are the expert on a tv show called gardeners question time and that they need to give advice to the concerned gardener explaining why his seeds did not grow. How many ideas do they have?

Main activity Explain that the children are going to perform an experiment to find out if seeds need water to start growing. Ask them to make a prediction and write some of the predictions on the board. Now ask them to plan an experiment to find out the answer. This activity can be done in pairs or groups so that the children can support each other. Typically children will say that they should plant the seeds in a pot, give them water and see if they grow. You will probably need to prompt children of this age to consider the benefit of also planting some seeds in a different pot that is not watered for the purposes of comparison. Once you have discussed fair testing with them ask them to carry out the experiment that they have planned.

Fair testing An important idea to start introducing to children is the idea of a fair test. A good way to do this is by suggesting unfair testing e.g. “ Why don't we use radish seeds for the watered pot and cress seeds for the unwatered pot?” Try to encourage the children to begin to realise that for a test to be fair everything has to be constant except the one thing that is being tested.

Recording results This experiment is probably best recorded in the children's science books in the form of drawings. Have the children concentrate on drawing the two pots at the beginning of the experiment. Explain that there is no need to draw themselves (otherwise that is what they will put most effort into) and that the pictures should be large enough and clear enough to see the seeds. Once the seeds have had time to germinate, ask them to redraw the pots showing what has happened. What conclusions can they draw?

Practical tips. I like to use petri dishes instead of pots because they are disposable and have lids that prevent the watered pots from drying out and ruining the results. Seeds do not need sunlight to germinate! Putting them on the windowsill will cause then to rapidly dry out. I suggest putting them in a fairly dark (but not cold) place in the classroom. Labels are your friend. It seems obvious but it is vital that all pots are labelled as watered or not watered. If the children forget to do so then the results are ruined. It's best to use a fast germinating seed for this such as cress which will germinate within a week. Make sure that the children put at least 5 seeds in each pot to account fro natural genetic variations in the seeds.

First plenary As it will take a week for the seeds to germinate this first plenary could consist of a question and answer session. “Why are we doing this experiment? What are we trying to find out?” “How will we know the answer to our question when we look at the pots next week?

Results. Once the seeds have germinated. Ask the children to draw the pots in their books again and to compare them to the week before. Do their results tell them anything? Are they able to say if seeds need water to grow or not?

Second plenary Remind the children of the letter from the concerned gardener that prompted this investigation. Ask them to make up a TV show episode about this letter. If your school has a video camera this show could be recorded, otherwise make a giant TV screen out of a large cardboard box and allow the children to use that.