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Unit 9 · Matter

Elements and Atoms Presentation

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Unit 9 · Matter

Elements and Atoms

Science & Technology · Grade 7

Learning Objectives

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Define an element and say why 118 kinds are enough for everything

⚛️

Describe an atom, its nucleus and its shells

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Give the mass, charge and location of proton, neutron and electron

🔢

Work out atomic number and atomic weight, and say what fixes identity

What an Element Actually Is

  • Cannot be broken into anything SIMPLER by a CHEMICAL process
  • Hammer copper into dust and the dust is still copper
  • Small is not the test: sugar is tiny, and it is not an element
  • 118 in all: 92 natural and 26 artificial. That is the whole list
MATTER solids, liquids, gases PURE SUBSTANCE MIXTURE physically combined into ELEMENT COMPOUND chemically combined into HOMOGENEOUS HETEROGENEOUS iron, gold, oxygen water, salt salt in water sand in water This whole topic lives in one box: the ELEMENT box at the bottom left.

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Presenter notes: Ask the class to count how many different substances they can see from where they are sitting, and let the list grow: wood, glass, chalk, cloth, paper, plastic, water, air, skin, ink. Then tell them that every single one of those, and every substance anywhere on Earth, is built from just 118 kinds of building block. Not thousands. A hundred and eighteen, and only 92 of those occur in nature. Ask how that can possibly be enough, and do not answer. Say that today they will meet the building blocks, and that a single number decides which one you are holding.