EFFECT OF CHANGE OF PRESSURE :
We have already learnt that the difference in various states of matter is due to the difference in the distances between the constituent particles. What will happen when we start putting pressure and compress a gas enclosed in a cylinder? Will the particles come closer? Do you think that increasing or decreasing the pressure can change the state of matter?
Fig. By applying pressure, particles of matter can be brought close together.
Applying pressure and reducing temperature can liquefy gases. Have you heard of solid carbon dioxide (CO2)? It is stored under high pressure. Solid CO2 gets converted directly to gaseous state on decrease of pressure to 1 atmosphere* without coming into liquid state. This is the reason that solid carbon dioxide is also known as dry ice. Thus, we can say that pressure and temperature determine the state of a substance, whether it will be solid, liquid or gas.
Fig. Interconversion of the three states of matter
State whether the following statement is true or false :
Solid carbon dioxide is stored under low pressure.
Fill in the following blank with suitable words :
Gases can be liquefied by applying ....................... and lowering .....................