# 3. Solving problems through experiments

For the final part of this section, we build on the ideas in the first two sections to ask pupils to solve the problem in the Key Activity (read this now). This activity uses investigative skills – predicting, planning, recording and presenting findings. Does this kind of activity keep your pupils interested? Can you think of other topics in the science curriculum where you could use this? Share your ideas with your colleagues. Perhaps you could start a journal of investigations in your school.

Often, in science, the unexpected happens. In Case Study 2, one teacher uses a demonstration to challenge his pupils’ thinking – he shows that a metal needle floats. How is that explained? This type of activity gives you an opportunity to assess pupils’ understanding and to add to your original class mind map.

## Case Study 3: A needle floats – exploring surface tension

Barnabas Lyere had always been delighted by surprises as a child. In his science teaching he enjoyed finding unexpected ways to demonstrate the facts found in textbooks. This short demonstration certainly surprised his pupils and made them think carefully about the nature of water.

He gathered together an open glass bowl, two-thirds full of water, a few ordinary steel sewing needles, scissors and a double-ply sheet of toilet paper/tissue.

First, he asked the pupils to predict what would happen if you placed a needle on the surface of the water. They were all confident that it would sink. Barnabas let one of them try it – their prediction was right.

Next, he took another needle and cut a small rectangle of tissue slightly longer than the needle and about 2 cm wide. He peeled apart the two layers and rested the needle on one of the rectangles. Carefully he lay both on the water. ‘See! It floats,’ he told his class. They all said he was cheating. But then, as they watched, the tissue became waterlogged and sank, leaving the needle floating on the thin skin of the surface.

Barnabas didn’t give any explanation. He asked his pupils to discuss their thinking and questions in small groups. Then he asked them to suggest explanations for what they had observed and he shared some ideas about surface tension.

At the end of the lesson, some of his pupils added the new information to their original mind map about water. (Resource 5: Surface tension gives background information for you, the teacher.)

## Key Activity: What is the best way to dry a cloth?

• Organise your pupils into groups of four.
• Give each group a piece of cloth or paper towel to wet and then cut up. Now ask them to think of the best way to dry the pieces of cloth. Should the cloth be – crumpled up? Folded up? Spread out? In the sun? In the shade? In a draught?
• Each group should make a prediction and plan their experiment. What equipment will they need? What will they measure? How will they present their results?
• Discuss with your pupils the need to keep everything the same except the one thing they are investigating – here, this is their method of drying. So they will need to make sure that each piece of cloth is the same size and have the same amount of water on it at the start.
• When groups have their plan and their equipment, let them try their investigation.
• Each group should present their findings to the class; they should include the best way to dry the cloth and things that went wrong in their investigation.

2. Focus on drinking water

Resource 1: Surviving in the desert