“Exploration of the Properties of Water”
Authors
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| National Statements of Learning |
Activity Links to National Statements of Learning for Science
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| Organiser | Year 3 |
Year 5 |
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| Science as a human endeavour | X |
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| Science as a way to know | X |
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| Science as a body of knowledge | Energy and Force | ||
| Matter | X |
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| Living Things | |||
| Earth and Space | |||
Standard 2
·Science as a Human Endeavour stages 4-7
·Scientific Inquiry stages 3-8
Discuss with the class the behaviour of ice bergs and ice blocks in water. The ice floats and about 10% is partially visible above the surface of the water. The water molecules in an ice block/ice berg arrange themselves in such a way that they take up about 10% more space than the liquid form. This expansion means the ice is less dense and the extra 10% of volume is what we see floating above the surface.
Class Activity and Question for Investigation:
How does a coloured cube of ice react when placed in a beaker of oil and water?
Ask students to predict what will happen when water and oil are mixed together and then an ice cube is added.
Which of the three is the heaviest?
What will happen as the ice melts?
Explanation- (to guide class discussion during the activity).The oil sits on top of the water as it is less dense than water. The ice is less dense than both the water and oil and sits on top of the oil The beaker is nearly full and the ice cube sits above the top of the beaker. As the ice cube melts the heavier coloured water drops travel down through the oil and into the water beneath. The water (separated by the oil) gradually changes colour. As the ice cube melts the beaker does not overflow. This is because the water molecules contract and lose the additional volume gained in the freezing process.
Further question for discussion:
Why is global warming a serious problem if ice contracts and takes up less space(volume) when it thaws?
The problem arises when land based ice melts as this is not part of the existing volume of sea water.
Discuss dissolution and examples of substances that will dissolve in water eg salt, sugar, jelly crystals, sodium bicarbonate.
Questions
What happens to sugar when it dissolves in water?
The sugar particles break down into individual sugar molecules that are too small to be seen by eye and mix with the water molecules. The sugar and water molecules are compatible with each other and this allow the mixing to occur.
Why didn’t the oil in our first experiment mix with the water?
Oil molecules are not compatible with water molecules and do not mix. If you try to mix them they separate again into separate layers after you stop stirring or shaking.
What are some ways we could prove the sugar is still there?
(Weigh the sugar and water separately and see if the weight of the solution equals the combined weight or try making the solution at home and tasting it.)
Discuss what factors (variables) might change the rate at which sugar will dissolve eg the temperature of the water. Draw a table and list these factors (variables) -see below.
Explain to the students that they will be measuring the effect of changing just one variable -the temperature. This will then be a fair test for measuring the effect of temperature on how fast sugar dissolves.
| What we keep the same (variables) | What we will change(independent variable) | What we will measure(dependent variables) | |||
| The amount of sugar - one cube | The temperature-chilled water, tap water and hot water | Amount of sugar dissolved at each temperature. | |||
| The type of sugar - white sugar | |||||
| The amount of water | |||||
| The presentation of the sugar - cubes (no loose crystals) | |||||
| What we do after the sugar is added-let sit, no stirring | |||||
| The time - 30 seconds* |
*Repeat the test at 60,90,150 and 180 seconds at each temperature to generate more results
See the attached rubric for student self assessment of unit outcomes