IS HEATING THE ONLY WAY TO CAUSE CHANGES OF STATE?

As well as heating or cooling, changing the pressure acting on a substance can also cause it to change state. If the pressure on the molecules in a substance is increased, it becomes harder for them to move apart from each other, so the temperature at which they become a liquid is increased. Similarly, at low pressure, changes happen at lower temperatures. It is impossible to make a good cup of tea or coffee’ at the top of Everest, for. example, because water boils at a temperature almost 30°C (50°F) less than at sea level.

All matter can move from one state to another. It may require extreme temperatures or extreme pressures, but it can be done. Sometimes a substance doesn’t want to change states. You have to use all of your tricks when that happens. To create a solid, you might have to decrease the temperature by a huge amount and then add pressure. For example, oxygen (O2) will solidify at -361.8 degrees Fahrenheit (-218.8 degrees Celsius) at standard pressure. However, it will freeze at warmer temperatures when the pressure is increased.

Some of you know about liquid nitrogen (N2). It is nitrogen from the atmosphere in a liquid form and it has to be super cold to stay a liquid. What if you wanted to turn it into a solid but couldn’t make it cold enough to solidify? You could increase the pressure in a sealed chamber. Eventually you would reach a point where the liquid became a solid. If you have liquid water (H2O) at room temperature and you wanted water vapor (gas), you could use a combination of high temperatures or low pressures to solve your problem.

One winter day, you sit by a window inside your warm home. You watch the snow pile up on the ground. You see small animals slide across a frozen pond in your backyard. You can see their hot breath as steam clouds in the cold air. You are drinking a cup of cocoa. You see steam rising from the mug, and you know it is too hot to drink. So you add an ice cube to the cup and wait for the melting ice to cool your cocoa. Solids, liquids, and gases are all around you. The solid ice in the pond, the liquid cocoa, and the steamy air are different states of matter. What is matter? How are solids, liquids, and gases different? Why did the solid ice cube melt into liquid when you put it into your cocoa?

Picture Credit : Google