Summary for pages 36-39:
Matter is Made of Atoms
What we know about matter is based on macroscopic observations.
Scientific explanations are not always accurate. They often provide a way to think about why things happen.
A microscopic model will help explain more about the behaviour of matter.
2-7 Atoms
Matter is composed of atoms.
An atom is the "smallest possible piece" of something.
Spheres are used by chemists to represent atoms.
2-8 Elements
An element is a substance that cannot be broken down and can exist as a solid, liquid, and gas.
Solids hold their shape because the atoms are stuck together but still vibrate.
When the temperature rises, atoms flow past each other and the liquid takes the shape of container.
At the boiling point, atoms move far apart. The liquid turns into a gas.
Particles made of more than one atom are called molecules.
Elements have different melting and boiling points. Generally, larger particles have a higher boiling point.
2- 9 Compounds
All compounds are composed of two or more more kinds of atoms.
Molecules have definite shape and composition.
A compound can be decomposed when heating and electrolysis occurs.
Not all compounds are composed of molecules.
Ions are particles with an electrical charge.
Ionis compounds form ions; molecular ions form molecules.
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