Academic journal article The Science Teacher

Professors Devise Simple Climate Change Demo

Academic journal article The Science Teacher

Professors Devise Simple Climate Change Demo

Article excerpt

An experiment developed by physicists at the Queensland University of Technology (QUT) in Australia uses Archimedes' principle to demonstrate that oceans expand as they heat up, causing sea levels to rise, even without factoring in melting ice sheets.

"This process is called thermal expansion--a concept that's traditionally been very difficult to demonstrate in a teaching lab because one litre of water will expand by only 0.2 ml per degree Celsius," says Stephen Hughes of QUT. "This new experiment uses a glass marble immersed in a beaker of water, with the marble suspended by fishing line and paper clips from an overhead electronic balance. "The weight of the marble increases as the water is warmed because water loses buoyancy as it expands and its density decreases."

Archimedes' principle describes how the weight of an object immersed in water is reduced by an amount equal to the weight of the water displaced. Hughes says this law of buoyancy means the buoyancy of an object changes if the water density changes. For example, if a ship were to travel from the Arctic to the tropics it would float lower because warm water is less dense than cold water," he says. "We're using the same effect--except with glass marbles on a much smaller scale. My first-year physics students find the experiment quite easy because the volume of the marble can be measured precisely by the instructor before the experiment and the students can read all the other measurements they need directly from digital instruments and without needing to take great care to measure the volume. …

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