Jelly good solutions

23rd February 2001 at 00:00
John Stringer describes how a Year 4 class got into hot water and earned top marks from OFSTED.

One particular risk always accompanies practical science - the risk that it might not work. This lesson focused on "Solids, liquids and how they can be separated", with an emphasis on learning the skill of managing a fair test. An element of risk was involved here - not just that it might not work, but also that the classroom could become awash with water and jelly cubes.

The teacher minimised that risk by giving the children prior experience of dissolving materials - so that they were unlikely to try to dissolve their jelly cubes in a teaspoonful of water - and by structuring the lesson carefully, so that the children had an element of choice and, therefore, ownership of the investigation. They chose whether to look at solutions made with water at different temperatures (not measured, since this would introduce complications), or with different amounts of stirring, or with jelly cubes of different sizes, or indeed of different colours.

What made this lesson a winner were these elements: lThe activity was set in a context - in this case, making a jelly in a hurry for a children's party. At the end of the lesson, the teacher returned to the main point: what would be the fastest way to make a jelly?

lThe children had to look for possible risks. The teacher was looking for an understanding that hot water might soften the plastic cups, but the children also suggested that jelly cubes on the floor would be slippery.

* The teacher looked for an explanation of the results. It wasn't sufficient that the children made an observation - for example, "the warmer the water, the faster the cube dissolves". They also had to explain why they thought this made a difference. One boy said, "If you cut the cube into small pieces, the water has more jelly to get at".

* The children evaluated their evidence. Some concluded that, although stirring worked for a raspberry cube, it might not work for a lime one. The teacher suggested that it might be a good idea to try the investigation more than once. They also evaluated how well they had done the testing. How would they improve on their technique next time? "Part way through, we got bored and so we stirred it. But we stirred the bits harder than the whole cube. So that wasn't fair."

* Finally, the teacher brought the whole lesson back to the original problem: "So how can make this jelly in a hurry?" The class knew that small pieces, warm water and stirring were the keys to speedy dissolving. Except for one child who wanted to microwave the cubes. "Now, would that be dissolving - or melting?"


Subject: Science

Class: Year 4

Whole class splitting into groups with learning assistant support.

Lesson time: Thursday 10.45am-11.55am Previous learning * The children had dissolved salt and compared this with what happens when sand is added to water.

* They had recognised, with support, that a solution is clear.

* Some of them had suggested that there were techniques that could have made the salt dissolve faster.

* They had used stopwatches when looking at "Moving and Growing".

Learning outcome * To understand that warm water, stirring and cutting a jelly into small pieces speeds up the process of dissolving it in water, and to suggest some reasons why.

* To revise planning a fair test and to practise using a stopwatch.

Activitydifferentiation Context of party catering.

Discussion: 5-10 minutes Planning the investigation * Focus questions: What are we going to change? What are we going to measure? What are we going to keep the same?

* Safety: Are there any risks to us?

* Reminder: How to use a stopwatch.

* Activity: Jelly cubes, warm and cold tap water, spoons, plastic cups, scissors, stopwatches - 20-30 minutes.

* Learning assistant to support group three.

Lesson development * Questioning: What have you changed? Why did you do that? How do you know that made a difference? How much faster did the jelly dissolve after your change? How do you know the cube had completely dissolved? What did you keep the same? Why?

* Presentation of results: Groups to explain what they did and what they found in turn. Invite possible explanations (10-15 minutes maximum).

* Assessment: This should be on the children's understanding of why they compared their changes with a "control" jelly cube.

* Recording: A sheet should be prepared with emphasis on explanation and some leading questions, for example: "Why do you think that happened?" "What might have happened ifI?" Results should be recorded in a prepared table (10-15 minutes).

* Conclusion: How good was our evidence?

What could we do better next time? (5 minutes) Evidence to be kept for follow-up lesson on transferring data to a bar chart.

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