Solids, Liquids and Gases: Ice, Water and Steam

Water exists in three states – solid ice, liquid water and gaseous steam. Solids have a fixed shape and size. Liquids can change in shape, but have a fixed size. Gases can change shape and size. Ice Water freezes at 0 degrees Centigrade and becomes ice. On a cold, dry, …

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Keeping Warm or Cold: Insulation and Conduction

Heat travels through solids by conduction (see also ‘Detecting Fake Silver: Conductivity of Metal’). Insulation can keep things warm and keep things cool by reducing heat transfer through conduction. Insulation can also help reduce heat loss through convection (the way heat travels through liquids and gases) and radiation (the way …

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Vibrations: Seeing and Feeling Sound

Sounds are created from vibrations, whether it’s a tuning fork, the reed of a musical instrument, or sound coming from someone’s voice box. The vibrations make the air molecules move backwards and forwards, creating something called a compression wave. The first set of air molecules pushes against the next set …

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Surface Tension: Keeping Bubbles Round and Insects Up

Water molecules at the surface of a glass of water are more strongly attracted to each other than to water molecules in the rest of the water. This creates a kind of ‘skin’ at the surface of the water, called surface tension. Water Droplets and Bubbles Run a tap slowly …

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Warm and Cold: Heavy Water

Hot water has more energy than cold water. This makes the water molecules move around more. Molecules that move more take up more space, but still weigh the same, so cold water is denser than hot water. The denser cold water sinks and the less dense hot water rises (see …

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Warm and Cold: Expanding Air

As air gets warm, the air molecules have more energy and move around more, taking up more space. As the warm air expands, it becomes less dense (see ‘Floating and Sinking: Looking at Density’) than the cold air, so rises up and floats above the cold air. Water acts in …

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Action and Reaction: Balloons in Flight

Sir Isaac Newton was born in 1643 and died in 1727. He was a physicist, mathematician, astronomer, biologist and chemist. Newton developed three laws of motion, which described how things move in response to forces (things like ‘pushes’ or ‘pulls’). Newton’s Third Law states that, “to every action there is …

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Pulling and Pushing: Magnetic Attraction

Magnets are attracted to some metals, and can attract and repel each other. The earth has a magnetic field, and so magnets can be used to find directions. Magnets and Magnets Magnets attract or repel other magnets. Put a bar magnet on a table and move the end of another …

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