this is msj chem in this video i'll be looking at the states of matter the three states of matter we look at in this video are solid liquid and gas here we can see the particle arrangement for each of the states of matter the particles in a solid are held in fixed positions therefore solids have a fixed shape and a fixed volume in a liquid the particles are able to move more freely than in a solid therefore liquids have a fixed volume but no fixed shape and finally we have a gas in a gas the particles move freely at high speeds with very weak forces of attraction between the particles for these reasons gases have neither a fixed volume nor a fixed shape next we look at changes of state so going from left to right we have a solid to a liquid which is melting liquid to gas can be either evaporation or boiling the change of state from a solid directly to a gas with no liquid phase is known as sublimation so next we'll go from right to left a gas changing state to a liquid is condensation a liquid to a solid is freezing the change of state from a gas directly to a solid with no liquid phase is known as deposition and finally we look at state symbols state symbols show the physical state of a substance S stands for solid alpha liquid G for gas and aq for aqueous AQ is used for solutions formed by dissolving a solid in a liquid so here we have an example of a chemical reaction that involves all four state symbols so in the reaction solid sodium reacts with water which is a liquid to form an aqueous solution of sodium hydroxide and hydrogen gas