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Unit 9 · Matter

Matter and Density Presentation

ScienceSubject
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Unit 9 · Matter

Matter and Density

Science & Technology · Grade 7

Learning Objectives

🧱

Say what counts as matter, and what does not

📦

Define density and explain why equal volumes can differ in mass

➗

Use D = m ÷ V to find any one of the three quantities

🔍

Explain why density identifies a substance but mass does not

What Counts as Matter

  • Matter is anything that has mass AND takes up space
  • Air, water, soil, stone, wood: all of them are matter
  • Shadow, heat and light are NOT matter. No mass, no volume
  • Three states: solid, liquid and gas
A chart of the three states of matter with beakers of solid, liquid and gas at the top and everyday examples below

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Presenter notes: Bring in a small iron nail and a large ball of cotton wool, and ask which is heavier. Everybody says the cotton, because it is enormous. Weigh them and let the nail win. Then ask the question that runs the period: why did everybody get that wrong? Because we judged by size, and size is not the same as amount of stuff. Tell them that today they will learn a single number that keeps the two apart for ever, and that this number is also how a jeweller can tell real gold from a fake without cutting it open.