2 The nature of matter In this chapter, you will find out about: ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆
the three states of matter, and changes of state separating and purifying substances filtration use of a separating funnel evaporation and crystallisation distillation paper chromatography criteria of purity elements and compounds atomic theory
Lord of the rings Saturn is perhaps the most beautiful of the planets of the Solar System. It has fascinated astronomers because of its mysterious rings (Figure 2.1). The Pioneer, Voyager and Cassini–Huygens space-probes sent back a great deal of information on the nature of the rings and the mass of Saturn itself. Each ring is made up of a stream of icy particles, following each other nose-to-tail around
Figure 2.1 Saturn and its rings silhouetted against the Sun: a photograph taken by the Cassini probe. The rings are made of ice and dust.
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the kinetic theory and changes of state diffusion Brownian motion atomic structure and subatomic particles proton (atomic) number and nucleon (mass) number isotopes relative atomic mass uses of radioactivity the arrangement of electrons in atoms.
the planet. The particles can be of widely varying sizes. The rings resemble a snowstorm, in which tiny snowflakes are mixed with snowballs up to the size of a house. The ice that surrounds one of the most spectacular planets of our solar system is made of water – the same substance (with the same formula) that covers so much of the Earth’s surface. The planet of Saturn is made of gases, mainly hydrogen and helium. Deep in the centre of these lightweight gases is a small rocky core, surrounded by a liquid layer of the gases. The hydrogen is liquid because of the high pressure in the inner regions of the planet nearest the core. The liquid hydrogen behaves with metallic properties. Study of Saturn’s physical structure emphasises how substances that we know on Earth can exist in unusual physical states in different environments. How do changing conditions affect the appearance, properties and behaviour of different substances?
Original material © Cambridge University Press 2014
Chapter 2: The nature of matter
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