Week 5 Double Class 80 minutes
We have four 1st year science classes, and we have three science labs. The timetabling this year has all first year science classess scheduled at the same time. We have set up a rota for the labs and this week I was in the classroom for the double period. I decided that I would continue with the food tests and complete 3 out of 4. I planned for the test for starch, the test for protein and the test for fat. I will do the test for reducing sugar in the next single class when I have the hotplates in the lab.
When I arrived at the classroom, I was diverted to the Technical Graphics room, as there was a speaker in for TY in the science demo room (the tiered room in most schools around the country!). We set off for the tech graph room at the other end of the school, 12 A0 whiteboards, markers, one basin of water, the food test experiment box and 20 first years in tow. On arrival, a quick rearrangement of the room and a note to myself that there was a carpet floor in this room. We stored the drawing boards to the side of the room and rearragned the double desks into three groups. There were six students at each double table, split into two groups of students for the double class. There was no laptop in this room, but there was a projector. I asked the students to bring in four foods each, that they would be interested to test for food types. Inevitably, some students did not bring food samples, while other students asked did they have to test the chocolate as they would really like to eat it at lunch!!
Task 1: Design an experiment to test for starch.
Student worked in groups of 3. I set my stopwatch to 8 minuites. I reminded them to make a title, list your apparatus (I highlighted the spelling of this as from correcting their scrapbooks this required correcting), write your proposed method, design a results table, leave a space for your conclusion and draw a labelled diagram. I questioned them: What might make a fair test? What is a control? What substance is readily available to you, that you know does not contain starch? Do most animal/plant products contain starch? What do you think? What substance is available that is not derived from plants or animals? It took students a long time to discover that water could be their control. I resisted telling them and it was difficult. There were light bulb moments and cheers as students realised it was water. This part of the class generated quite alot of noise at times. I am not sure whether it was more noise that in the lab or whether I was more conscious of the noise as I was in a different part of the school with other classes nearby. Some students had tested food for starch in Primary school, however, they did not design and experiment and the nature of experimental design is new to them. I think that this was a good experiment to ask them to design as they had some prior knowledge. They also came up with designs which were not viable but which allowed me to pose questions to deepen their understanding. For example, one student suggested crushing the food in the mortar and pestle, adding water to make it a liquid, draining the liquid through a sieve and he wanted to see if he could see the sugar particles in the sieve because starch is a sugar. I asked him a few questions: Do you think the sugar/starch particles are big enough to be trapped in a sieve? Do you think you could see them if they were? Finally, as a scientist, if you could see the sugar/starch, is that proving that they are sugar/starch? When you say sugar, do you mean carbohydrate?
We have chosen a textbook, Catalyst. We chose this book as it is based on an enquiry approach to teaching science. The students will purchase an ebook only and we will have 24 copies of the book in each lab, should the teacher wish to use it in class.
After ten minutes, students presented their title, apparatus and method to the class. Each group was given a spotting tile, mortar and pestle, droppers, and iodine dropper bottle. The groups carried out the test for iodine on four food types. They discovered the colour change. They learned that the colour change is the result. They learned that a conclusion is explaining why this happened - because starch is present. They also realised the importance of water as a control as they said they could look back to see the original colour and compare.
Task 2: To design an experiment to test for protein
I allowed them to discuss and debate their method on their whiteboards for five minutes. It was interesting that most groups decided that Iodine was the chemical they would use again. When I questioned them on this, 'if you used Iodine to test for protein then how do you know the difference between the test for starch and the test for protein?' They realied there must be a difference chemical reagant used. At this point, I informed them it was called Biuret solution. I gave each group a dropper bottle of Biuret. They straight away said 'ok it is blue so that colour change is blue -> __________'. All groups tested four foods for protein using a mortar and pestle, dropper and spotting tile.
Task 3: To design and experiment to test for fat
I began this task in the same way. I asked them to design the experiment using the headings. The students were more confident at this stage and I think designing the three experiments in the same double was hard for them but it helped them to apply and think through the scientific method many times, while working as part of a group. It was difficult for me to allow them to discover the method and I really had to resist telling them!!
There are personalities emerging and disagreements are beginning to appear, where certain students are asking to move group and they realise who they like to work with and who they work well with. This is something I will need to think about and monitor. I think mixed gender groups, and pre planned mixed ability groups will be implemented strictly from here in.
In this taask, the students applied their knowledge that water should be used as a control and that it 'dried out and left no mark'. They also noticed how the brown paper 'went see through' and 'didn't dry out' when compared with the paper that they put water on. They recorded their result and their conclusion.
I thought of this on the spot, as I think being in a different place and with the move, I felt they were unsettled. I used a simple strategy today which I explained near the beginning of the class, when I realised that I needed it. When I out my hand up, all students must stop what they are doing, face me and put their hand up. This signalled I had an instruction or something to say. This worked well for me today and all students responded well to this.
I will assess their knowledge and understanding by grading their experiment reports by comment only. I am interested to see how they write up their reports.
1. Write a scientific report for the three scientific experiments that you designed in Science Matters experiment book.
2. We stuck in the learning intention: 'Conduct investigations to find out the biomolecules present in different foods' Write a reflection in your scrapbook on your experiences of designing and carrying out the experiment - refer to the key skills that you applied and the learning intention in your reflection.