Again, with Dale Tunnicliffe and early science… she points out:
“Things in our world change. The amount of light we have changes, from a lot during the day when the sun shines, to there being hardly any at night, when the only light comes from the moon because our part of the earth has turned away from the sun. The weather changes; it may rain or be fine, be calm or windy, hot or cool, humid or dry.” (p.115)
In this chapter, Dale Tunnicliffe offers activities designed “to help children recognize everyday changes and some yearly ones” (p.118), because “Change is a part of everyday life, so much so that we take it for granted and often do not notice it.” (p.118)
I’m interested in how she presents ‘change’, pointing to the seasons, the changes plants and animals undergo, the changes in sound and light in our environment, and the changes that happen when materials are combined.
Under the following headings, she writes:
Change of state
“Water changes state and can alter its form – from solid (ice), to liquid, to gas (steam). Steam can be seen rising from the spout of a boiling kettle, and is the process of heated, gaseous water reforming as a liquid. Some changes are reversible, for example chocolate melting, water vapour condensing on a cold surface and puddles evaporating into the air. Heating materials can bring about physical changes: the things melt and change what they look like. When candle wax gets hot when the candle is lit, it melts to form molten wax. Ice cream when heated becomes runny as the ice in it melts and changes to water.
Likewise, cooling materials down can also cause physical changes; cooling a liquid can turn it into a solid. This is seen when making ice cubes or ice-lollies in a freezer, for example, or when molten candle wax or runny chocolate cool and solidify. When some foods are cooled they become hard, like food taken directly from the freezer. Frozen food has to thaw out and the water in it become liquid again before we can eat it.” (p.117)
“Sometimes different kinds of solids are found together in mixtures and need to be separated. This can be done by sieving; alternatively, if the solids are in a liquid, often the solid will sink to the bottom of the container (gravity working!) and the liquid can be poured off. This is decanting. Solids can be separated from liquids by a sieving process where the solution is poured through a material with holes in, such as a colander, to drain the water off. Examples of this sieving are straining peas with a sieve or colander from the water in the saucepan in which they have been cooked or tea strainers catching loose-leaf tea when the tea is poured out from a teapot. Filter paper can be used to filter liquid away from the solids, which stay on the paper, like coffee filters. Kitchen towel pieces can be used as a filter when put inside the inverted cut-down top of a soda bottle. If, however, the solid has dissolved in the liquid, like sugar put into hot water, filtering does not work. Then other methods have to be used. One way to take the liquid away from sugar dissolved in hot water is by heating it, causing the water to evaporate. This change is reversible; if changes are chemical, for example adding acid (vinegar) to sodium bicarbonate (baking soda), which makes bubbles of gas (carbon dioxide), they cannot be reversed. The gas cannot be put back into the bicarbonate powder.” (p.117)
Changing things permanently
“Chemical change is when materials used break down and are permanently changed into something else. Food items are cooked and in this way we change our food, e.g. potatoes change from hard to soft pieces. Some foods change colour when they are cooked: fried meat becomes darker and white rice, which is hard before it is cooked, becomes soft and white. Wood and paper burn to ash, and burnt bread becomes burnt toast with [-p.118] black carbon. Cooking is all about heating cold substances, which then change, as in mixing flour, milk and eggs and making a new substance from the constituents such as a cake. When eggs are cooked they change and cannot be changed back to the raw egg state. Oxygen reacts with some other chemicals in cut surfaces of apples and potatoes and turns the whitish surface brown.” (pp.117-118)
Key words Dale Tunnicliffe points to under the topic of ‘Changes’ include: “Solid, liquid, gas, change of state, mixers, separating, filtering, vapour, sound, light, electricity, metamorphosis, larva, imago, hibernate, dormant.” (p.115)
Ref: (emphases in blue bold, mine) Sue Dale Tunnicliffe (2013) Talking and Doing Science in the Early Years: A practical guide for ages 2-7. Routledge: Oxon and New York.