Answer:
(1). Going in the order: Gas, Liquid, Solid.
Particle separation: Very large; large; small.
Strength of forces between particles: very weak; weak; strong.
(2). a. The change of state is condensation.
b. The density of the substance is increasing as particles move closer together.
(3). a. The liquid's temperature decreases until it reaches solidification (freezing) point, and then the temperature will remain constant until all of the liquid has solidified.
b. The particles move with less and less energy until they have low enough energy to come together and solidify, then they will release more energy when they come together to form bonds, and vibrate about their equilibrium positions once they are part of a molecular bond.
Additional explanation:
(1). The particle separation in a gas is very large because the gas has a very low density, and since particles are not that close together,<em> the strength of forces between particles is very weak</em>.
The liquid is somewhat more denser than the gas and therefore the particle separation is large but less than that in a gas,<em> The strength of forces between particles is still weak but greater than in a gas. </em>
Finally, particle separation in a solid is small because the solid is still more denser than the liquid, and the strength of forces between particles is strong because it's these forces that give a solid its rigid shape.
(2). a.The change of state of a substance in which particles slow down and move close together is called condensation.
b. As the particles move close together, they are occupying less and less volume; therefore, the density is increasing.
(3). The explanation is already given in the answer.
= 40 x 1.5 x 1.5 = 90 kg/m^{2}