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Conservation of Mass

Produced by Teachers TV and part of the Great Lesson Ideas series, this video illustrates lesson planning ideas for experiments to help students explore the principle of conservation of mass.

First, the students mix colourless solutions of potassium iodide and lead nitrate together, to form a bright yellow mixture, demonstrating that a chemical reaction has taken place. They weigh the solutions before and after mixing, noting that the mass remains the same.
Next, students observe the reaction between marble chips and hydrochloric acid. The class discuss why the mass decreases in this reaction and conclude it is due to the loss of carbon dioxide gas.

Lastly, students see how popcorn kernels increase in volume when boiled, but the mass stays the same.

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