It is all the notes and all you need to know to score in IGCSE CIE physics and chemistry in the IGCSE course. this is notes for every topic in the course. This document is on the entire IGCSE CIE course.
The particle nature of
matter
- State the distinguishing properties of solids, liquids and gases
Solids
- Strong forces of attraction between particles, particles are packed very closely
together in a fixed and regular pattern
- Atoms vibrate in position but can’t change position or move
- Solids have a fixed volume, shape and high density
Liquids
- Weaker attractive forces in liquids than in solids, particles are close together in an
irregular, unfixed pattern.
- Particles can move and slide past each other which is why liquids adopt the shape of
the container they’re in and also why they are able to flow.
- Liquids have a fixed volume but not a fixed shape and have a moderate to high
density.
Gases
- No intermolecular forces, particles are in random movement and so there is no
defined pattern
- Particles are far apart and move quickly (around 500 m/s) in all directions, they
collide with each other and with the sides of the container (this is how pressure is
created inside a can of gas)
, - No fixed volume, since there is a lot of space between the particles, gases can be
compressed
- Describe the structure of solids, liquids and gases in terms of particle separation,
arrangement and types of motion
-
- Describe changes of state in terms of melting, boiling, evaporation, freezing,
condensation and sublimation
Melting
- Melting is when a solid changes into a liquid
- Requires heat energy which transforms into kinetic energy, allowing the particles to
move
- Occurs at a specific temperature known as the melting point (m.p.) which is unique to
each pure solid
Boiling
- Boiling is when a liquid changes into a gas
- Requires heat which causes bubbles of gas to form below the surface of a liquid,
allowing for liquid particles to escape from the surface and within the liquid
- Occurs at a specific temperature known as the boiling point (b.p.) which is unique to
each pure liquid
Freezing
- Freezing is when a liquid changes into a solid
, - This is the reverse of melting and occurs at exactly the same temperature as melting,
hence the melting point and freezing point of a pure substance are the same. Water
for example freezes and melts at 0ºC
- Requires a significant decrease in temperature (or loss of thermal energy) and
occurs at a specific temperature which is unique for each pure substance
Evaporation
- When a liquid changes into a gas. Evaporation occurs only at the surface of liquids
where high energy particles can escape from the liquid’s surface at low temperatures,
below the b.p. of the liquid
- The larger the surface area and the warmer the liquid/surface, the more quickly a
liquid can evaporate
- No heat is required and evaporation occurs over a range of temperatures
Condensation
- When a gas changes into a liquid, usually on cooling. When a gas is cooled its
particles lose energy and when they bump into each other they lack the energy to
bounce away again, instead they group together to form a liquid
- No energy is required for condensation to occur and it takes place over a range of
temperatures
Sublimation
- When a solid changes directly into a gas
- This happens to only a few solids such as iodine or solid carbon dioxide
- The reverse reaction also happens and is also called sublimation (sometimes called
deposition or desublimation)
- Sublimation occurs at a specific temperature which is unique for a pure substance
, - Explain changes of state in terms of the kinetic theory
Changes in State & Kinetic Theory
- When substances are heated, the particles absorb thermal energy which is converted
into kinetic energy. This is the basis of the kinetic theory of matter
- Heating a solid causes its particles to vibrate more and as the temperature increases,
they vibrate so much that the solid expands until the structure breaks and the solid
melts
- On further heating, the now liquid substance expands more and some particles at the
surface gain sufficient energy to overcome the intermolecular forces and evaporate
- When the b.p. temperature is reached, all the particles gain enough energy to escape
and the liquids boils
- These changes in state can be shown on a graph which is called a heating curve
- Cooling down a gas has the reverse effect and this would be called a cooling curve
- These curves are used to show how changes in temperature affect changes of state
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