The Material World class 2: more gases, and properties of materials

Our second class about The Material World went very well. Everyone was attentive and came up with great ideas about the topic.

The younger group (roughly KS1 or ages 5-7) repeated several of the activities from last week, to introduce ideas of different states of matter, and to reinforce these ideas for those who had already learned about them. They seemed to all have plenty of fun running around being gas particles.

I then introduced a few other activities to get them to think about gases and their properties: blowing bubbles, blowing up balloons and using a home-made balance to show that a blown up balloon does weigh more than an empty balloon. The exhaled air is not ‘nothing’ or ‘weightless’ as children often think. One of the children provided a great answer to why we don’t feel the pressure of air pressing down on us – we are used to it!

We talked about all matter being made up of particles. I arranged some ping pong balls on a metal grating in a regular pattern, and used a borrowed hairdryer to blow them around on two different speeds. This was based on an exhibit in the Science Museum in London which I always thought was a great way to show the kinetic theory of gases. Our hairdryer couldn’t get the balls moving at great speed so I also showed them a video a friend of mine had taken of the actual exhibit.

With the older group (KS2 or 8-10) I went through the same or similar activities, and then moved on to considering the properties of different materials.

– How can we tell that an object is one material and not another, for example plastic instead of wood, or metal?

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– What different properties do they have that make them appropriate or not for certain uses?

The boys closed their eyes and tried to guess what some objects were and what they were made of. I think if I do this again I will prepare some more fun objects with very different textures, densities and other properties. I might have to raid my little girl’s ‘treasure basket’ for these.

We wrote a list of different properties of materials which included colour, transparency, strength, electrical conductivity and thermal conductivity. The children were very good at coming up with ideas.

We had a great time testing materials for magnetism and for electrical conductivity. I was surprised to see that our Sydney tap-water conducts electricity pretty well even without anything else added, although our buzzer circuit was louder once we poured in some vinegar.

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The boys then started designing some objects and deciding what materials to use them for and why. I asked them to design one sensible version and one silly version. They will continue with this next week, which will give us more opportunity to discuss how designers choose the most appropriate material for their objects. We will then move on to using magnifying glasses to look at the structure of different materials.

As I said earlier, I was very pleased with this week’s class and I feel the groups are working well.

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