Science under your feet (30 min)
Start by asking the children to stamp on the spot, then “march” them outside asking them to think at all times what is below their feet – try to vary the surfaces you are walking on. The teacher should take a spade with them to dig out a cross-section of field/garden. Then ask questions, “what is below your feet, why did we not make a hole in the floor when stamping, what are puddles?
Demo: “looking below the sea” (to be set-up now, and discussed at the end of the day)
Take a bucket full of river sludge/water or seawater (inc sand & shingle) and pour it into a large settling-tower / clear plastic cylinder. Children make predictions about what will happen.
Looking at Rocks and Soil (45 min)
Take a large collection of rocks and soils so that each child can easily access 3-4 different ones. Provide a table to be completed by the children encouraging description of colour, size, shape, texture, can the rock be snapped – gross features. Then, using hand-lenses look closer and make predictions of porosity (for rocks only). Define porosity and think about how it could be tested.
Choose 4 stones and ask the children to place them in order of weight. Then make predictions about their weight, and, using scales, weigh and record the actual weight of the stones.
Demo: porosity
Pick 3 rocks (chalk, limestone, granite) and drop them into a large clear tank of water. Observe carefully and quietly (!!) – all will probably produce air-bubbles on their surface due to surface cracks and holes (bubbles produced from displaced air), but there will be a continuous flow of bubbles from the porous rocks (chalk & limestone) possibly accompanied by ‘whistling’
Porous Shapes & Absorbency (30 min): care with definitions of porosity & absorbency!!
Take up to 4 different soil samples (eg. Peat, sand, clay, peat & sand mix), and place the same amount of soil in 4 different tubes, note where on the tube the soil goes up to. Gently add an equal amount of water to each sample, observe what happens, shake the tubes gently and allow to settle.
Meanwhile, use a range of coloured card shapes, some of which interlock or fit tightly next to one another and others which don’t. Ask half the class to create a porous ‘rock’ and half to make a non-porous ‘rock’ by sticking the shapes to a piece of A4 paper. This will test their understanding of the term porosity and leaves time for the water to be absorbed by the soils.
Go back to the soil work, which soil has soaked up the most water and is therefore the most absorbent? If you use graduated tubes this works very well, 10 ml of soil + 10 ml water, does it give 20 ml? If less than 20, why? Clay or peat are the most absorbent. Discussion about spaces between soil particles, displacing air with water – what do plant roots grow through?
Rapid Rivers (30 mins)
Thinking about the deposition of rocks down a riverbed – large ones travelling shorter distances because they are heavier. The forces involve the movement of water.
First create your riverbed: guttering or half drain-pipes lined with white paper are ideal. Start with the top of the river slightly higher than the bottom. Get a bucket of muddy, stone-filled water (make your own if no river nearby) and giving everyone a turn, take out a beaker of the muddy water and “throw” it down river bed and observe the size distribution of the particles. After the first person has had their turn, subsequent waves of water will move the larger particles ‘down river’. Introduce a bend in the river and investigate further. We found the paper lining the riverbed to be essential otherwise EVERYTHING ends up at the bottom very quickly.