The melting & boiling point in deg. C of elements A, B, C, D & E are -189 & -186, -219 & -183, -7 & 58, 29 & 222, ....
660 & 2450 respectively. At room temperature (30 deg. C), which element(s) is/are solid(s), liquid(s), or gas(s) & what would happen to the particles of element C when it is cooled from 80 deg. C to -10 deg. C?
A, B, & C would be gases at room temperature because they boil (turn from a liquid to a gas) at temperatures below 30 C. D is a liquid at room temperature but it is just below its boiling point so a significant amount of it would probably be evaporating into the gas phase. Element E is a solid, probably a metal, due to its high melting point.
For element C, at 80 C it is completely in the gas phase. As it cools to 29 C it undergoes a phase change from the gas to the liquid (condensation). Once all the gas has condensed it continues cooling and at -7 C undergoes another phase change from a liquid to a solid (freezing). Once it is all solid the solid will then cool a further 3 degrees to a final temperature of -10 C.
Element A: Both melting point and boiling point are below room temperature therefore the element will be gas at room temperature.
Element B: Both melting point and boiling point are below room temperature therefore the element will be gas at room temperature.
Element C: Melting point is below room temperature and boiling point is above room temperature. Therefore the element will be liquid at room temperature.
When element C is cooled from 80 degrees C to -10 degrees C, the particles of the element will remain in gas form when cooled from 80 degrees C to 58 degrees centigrade. When cooled further the particles will five out latent heat of boiling and turn into solid without temperature drop. When cooled further after becoming liquid, the particle will remain liquid up to temperature of -7 degrees C. On being cooled further they will give out latent heat of fusion and become solid without drop in temperature. On further cooling after conversion to solid the temperature will again start dropping. The particles will remain in solid state on reaching the temperature of - 10 degrees C.
Element D: Melting point is below room temperature and boiling point is above room temperature. Therefore the element will be liquid at room temperature.
Element E: Both melting point and boiling point are above room temperature therefore the element will be solid at room temperature.