Michael Faraday was one of the most important experimental physicists who ever lived. His work in understanding and using electricity has allowed many of our technological advances in the last two centuries.

Solid, liquid or gas? - answers

Oxygen - gas
This makes up about 30% of air and was discovered in the 1770s.  It turns into a liquid at -183oC, and in liquid form it is a pale blue colour.

Iron - solid
Iron melts at 1538oC.

Hydrogen - gas
Hydrogen liquefies at -252.8Co.  It is used as a liquid fuel in rockets.

Chlorine - gas
Chlorine gas turns into a liquid at -34oC but it will turn into a liquid at room temperature if you apply enough pressure (i.e. squeeze it hard enough!).

Sodium - solid
Sodium is a solid at room temperature, albeit quite a soft solid.  Drop it in water and it breaks up the water molecules, releasing hydrogen gas.

Carbon dioxide - gas
At -78.5oC solid carbon dioxide (dry ice) turns directly into carbon dioxide gas (turning directly from solid to gas is known as 'sublimation').  To get a liquid you have apply pressure to the carbon dioxide.

Mercury - liquid
Mercury is the only metal that is a liquid at room temperature.

Curriculum Links

Getting colder


The particulate nature of matter

  • the properties of the different states of matter (solid, liquid and gas) in terms of the particle model, including gas pressure
  • changes of state in terms of the particle model


Particle model

  • the differences in arrangements, in motion and in closeness of particles explaining changes of state, shape and density
  • Ideas, political power, industry and empire: Britain, 1745-1901

Scottish Curriculum Links:


SCN 3-05a

Planet Earth - Processes of the planet

By contributing to experiments and investigations, I can develop my understanding of models of matter and can apply this to changes of state and the energy involved as they occur in nature

SCN 4-05a

Planet Earth - Processes of the planet

I have developed my understanding of the kinetic model of a gas. I can describe the qualitative relationships between pressure, volume and temperature of gases.

SCN 3-15a

Materials - Properties and uses of substances

I have developed my knowledge of the Periodic Table by considering the properties and uses of a variety of elements relative to their positions.

SCN 3-15b

Materials - Properties and uses of substances

Having contributed to a variety of practical activities to make and break down compounds, I can describe examples of how the properties of compounds are different from their constituent elements.


SCN 4-15a

Materials - Properties and uses of substances

Through gaining an understanding of the structure of atoms and how they join, I can begin to connect the properties of substances with their possible structures.

Getting colder

liquid chlorineIn the ten years between inventing the electric motor and the electric generator, Faraday didn't sit around doing nothing.  One of his key discoveries in chemistry was that it was possible to turn a gas into a  liquid.  We are most familiar with water, in the form of solid ice, liquid water and water vapour (gas).  To make something turn from a gas to a liquid to a solid we have to cool the substance down.  For some substance this is pretty tricky since the lowest temperature that occurs naturally on Earth is about -89C in the Antarctic - not very convenient for experiments!

Cooling a gas makes the molecules of the substance slow down and get closer together.  Since Faraday couldn't cool some of the gases to a low enough temperature he turned them into a liquid by squeezing their molecules together (pressurised).  There are gases under pressure around us all the time, air in balloons and the gas in a fizzy drink.  Although these pressures aren't great enough to turn the gas into a liquid!

Faraday started with chlorine (the image above shows a tube of liquid and gaseous chlorine), and in time managed to liquefy all of the known gases except for six, which included oxygen, hydrogen and nitrogen.  He couldn't get these to liquefy because they needed to be both cooled and put under pressure at the same time.

Key fact: To turn a gas into a liquid you need to cool it, put it under pressure, or do both at the same time.


Solid, liquid or gas?

Can you match the substance with how the atoms or molecules are arranged at room temperature (and pressure)?

Carbon dioxide

Take the quiz online here.