Week 1 · Unit 1 The Matter, opener; Lesson 1 Structure of the Atom (A): the atom as the building unit, Rutherford, protons, neutrons and electrons, energy levels · 3 lessons
1
Atoms: the building units of matter
Science Prep 1 Term 1, Unit 1: pp. 1–5
GoalSay what matter is and explain that everything is built from atoms, which are far too small to see.
New words
matter · anything that has mass and takes up spaceatom · the tiny building unit of all mattermolecule · a group of atoms joined together
Explanation
Matter is anything that has mass and takes up space: a stone, water, the air in a balloon, even you. Light and shadows are not matter. All matter is built from tiny pieces called atoms. A block of limestone, for example, is made of calcium carbonate molecules, and each molecule is built of atoms joined together. Think of a wall: from far away you see one wall, but it is made of many small bricks. Atoms are far too small to see, even with a school microscope. Long ago, Greek thinkers imagined that if you kept cutting a piece of matter into smaller and smaller bits, you would reach a last bit that cannot be cut, and they called it an atom. In the early 1800s the English scientist John Dalton built the first scientific atomic theory, based on experiments.
a block of limestone→calcium carbonate molecules→atoms
Worked examples
A balloon full of air shows that air is matter. The air takes up space, because it stretches the balloon, and it has mass. We cannot see it, but it is there.
Matter
Not matter
sand
torch light
juice
a shadow
a pencil
Which of these are matter? Sand, juice, torch light, a shadow, a pencil. Sand, juice and a pencil have mass and take up space, so they are matter. Light and a shadow are not.
Aya says: “A beach looks smooth from far away, but it is millions of grains.” Matter is like that too: it looks smooth, but it is built from atoms that are too small for us to notice.
Class activity
Tear and imagine. With an adult, tear a strip of paper in half, then tear one half in half again, and go on as long as your fingers can. When you cannot tear any more, stop. Now imagine a magic tool that keeps going. This is how the Greek thinkers pictured an “uncuttable” piece. Real atoms are far smaller than any paper bit.
Practice
1
What is matter?
Anything that has mass and takes up space.
2
Is a shadow matter? Explain.
No. A shadow has no mass and does not take up space.
3
Put these in order from biggest to smallest: an atom, a block of limestone, a molecule of calcium carbonate.
A block of limestone, a molecule of calcium carbonate, an atom.
4
Who built the first scientific atomic theory, and when?
