What Changes If The Degree (Amount) Of Intermolecular Bonds Of A Substance Are Changed?
The three states of matter
The three states of thing tin be represented past the particle model. This model explains the properties of substances in their unlike states, as well as changes of land.
Changes of country
The diagram summarises the common changes of state.
Some substances tin change direct from solid to gas, or from gas to solid, without becoming a liquid in betwixt. This is called sublimation . Solid carbon dioxide ('dry ice') and iodine tin can sublime .
Explaining change of state
Melting, evaporating and humid
Energy must be transferred, by heating, to a substance for these changes of state to happen. During these changes the particles proceeds energy, which is used to:
- suspension some of the bonds betwixt particles during melting
- overcome the remaining forces of allure between particles during evaporating or boiling
In evaporation, particles leave a liquid from its surface but. In boiling, bubbles of gas form throughout the liquid. They rise to the surface and escape to the surroundings, forming a gas.
The amount of energy needed to change state from solid to liquid, and from liquid to gas, depends on the strength of the forces between the particles of a substance. The stronger the forces of attraction, the more energy is required.
Every substance has its own melting point and humid point . The stronger the forces between particles, the higher its melting and boiling points.
The strength of the forces betwixt particles depends on the particles involved. For case, the forces between ions in an ionic solid are stronger than those betwixt molecules in water or hydrogen. This explains the melting and boiling point information in the tabular array.
| Substance | Bonding type | Melting point | Boiling bespeak |
|---|---|---|---|
| Sodium chloride | Ionic | 801°C | 1413°C |
| H2o | Pocket-sized molecules | 0°C | 100°C |
| Hydrogen | Small molecules | -259°C | -252°C |
Evaporation tin can have place beneath the boiling point of a substance.
Condensing and freezing
Energy is transferred from a substance to the environs when a substance condenses or freezes. This is because the forces of allure between the particles become stronger.
Predicting a physical state
The land of a substance at a given temperature tin be predicted if its melting point and boiling point are known. The table summarises how to work this out.
| Temperature | Predicted country |
|---|---|
| Given temperature < melting bespeak | Solid |
| Given temperature is between melting and boiling points | Liquid |
| Given temperature > boiling point | Gas |
- Question
-
The melting point of oxygen is -218°C and its boiling indicate is -183°C. Predict the country of oxygen at -200°C.
-
Oxygen will be in the liquid state at -200°C (considering this is between its melting and boiling points).
Limitations of the particle model
The particle model assumes that particles are solid spheres with no forces betwixt them. However:
- particles are non solid, since atoms are by and large empty infinite
- many particles are not spherical
Source: https://www.bbc.co.uk/bitesize/guides/z93jfcw/revision/2
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