General properties of substances in different states
The gaseous, liquid and solid states are characteristic not only for water, but also for most other substances. At room temperature, for example, iron is solid, water is liquid and helium is gaseous.
In the solid state, the molecules are close together and cannot move much relative to each other. That is why solids retain their shape. Solids can't easily be compressed because their particles are already tightly packed.
In the liquid state, the molecules are farther apart and more mobile than in the solid state. Therefore, liquids can flow and the shape of a liquid depends on the shape of the container in which it is kept. Just like solids, liquids can't easily be compressed because their particles are still too tightly packed.
In the gaseous state, the distances between molecules are very large, the molecules are mobile and fill any large space. Unlike solids and liquids, gases can easily be compressed.
Does it retain its shape? | How much can it be compressed? | |
Water vapor - gaseous | ||
Water - liquid | ||
Ice - solid |
What does the state of the substance depend on?
The state of the substance depends mainly on the temperature. Each substance has a certain melting point; for example, iron begins to melt when heated to 1535 degrees.
However, mercury is a metal that is liquid at room temperature, only freezes at –38.8 degrees, and evaporates at 356 degrees.
The state of the substance also depends on the pressure. For example, the household gas in the gas tank, which is strongly compressed and under high pressure, is liquid. When the gas exits the gas tank, the pressure decreases, so the liquid evaporates and becomes gaseous again.
- Iron
- Sugar
- Oil
- Water
- Carbon dioxide
- Oxygen
Think!
- How does the state of the water depend on the temperature?
Properties of the substance - volatility and fluidity
Substances evaporates most rapidly at their boiling point, but the particles start to evaporate at much lower temperatures. Volatility is a property of a substance that indicates how easily it evaporates. Volatility refers to the ability of the particles of a substance to separate from a liquid or solid. If a drop of petrol and a drop of water are left open, petrol will evaporate first, because it is more volatile.
Liquids can also be compared in terms of their fluidity - the ability to flow. For example, oil flows more slowly than water, and alcohol flows faster.
The state of the substance depends onand .
A measure of how easily a substance evaporates is called .
Liquids can also be compared based on their.
Important terms
- volatility – a measure of how easily a substance evaporates
- fluidity – the ability of a liquid to flow readily
I now know that…
In the solid state, the molecules are tightly packed together, that's why solids retain their shape. In the liquid state, the molecules are more mobile, that's why liquids can flow. In the gaseous state, molecules move freely and can be compressed. The state of the substance depends on the temperature and pressure.
