In some materials the solid goes directly to the gas without going through a liquid state. So the energy per particle is biggest for the gas and smallest for the solid. In one case 3 He you can actually make the liquid turn solid by heating it up. In that weird case the solid has more energy than the liquid. The reasons for that special behavior are too tricky for me to describe here.
It's something you may get to understand if you study physics further. Mike W. What happens when you take energy out of a gas? Related questions How do you calculate rate of reaction? How can rate of reaction be affected? How can rate of reaction be increased? How can temperature affect reaction rate? How can the rate of reaction be calculated from a graph?
How do reaction rates give information about mechanisms? What is a reaction rate constant? How do the reaction rates change as the system approaches equilibrium? Why does the rate of reaction increase with concentration? Why do rates of reaction change with pH? See all questions in Rate of Reactions. The opposite process, a liquid becoming a solid, is called solidification.
For any pure substance, the temperature at which melting occurs — known as the melting point — is a characteristic of that substance.
It requires energy for a solid to melt into a liquid. Every pure substance has a certain amount of energy it needs to change from a solid to a liquid. However, our quantity is given in units of grams, not moles, so the first step is to convert grams to moles using the molar mass of H 2 O, which is Because the substance is melting, the process is endothermic, so the energy change will have a positive sign. During melting, energy goes exclusively to changing the phase of a substance; it does not go into changing the temperature of a substance.
Hence melting is an isothermal process because a substance stays at the same temperature. Only when all of a substance is melted does any additional energy go to changing its temperature.
What happens when a solid becomes a liquid? In a solid, individual particles are stuck in place because the intermolecular forces cannot be overcome by the energy of the particles. When more energy is supplied e. This is the liquid phase: particles are still in contact but are able to move around each other.
This explains why liquids can assume the shape of their containers: the particles move around and, under the influence of gravity, fill the lowest volume possible unless the liquid is in a zero-gravity environment — see Figure The phase change between a liquid and a gas has some similarities to the phase change between a solid and a liquid. At a certain temperature, the particles in a liquid have enough energy to become a gas.
The process of a liquid becoming a gas is called boiling or vapourization , while the process of a gas becoming a liquid is called condensation. This means that the temperature at which a liquid becomes a gas, the boiling point , can change with surrounding pressure.
Therefore, we define the normal boiling point as the temperature at which a liquid changes to a gas when the surrounding pressure is exactly 1 atm, or torr. Unless otherwise specified, it is assumed that a boiling point is for 1 atm of pressure. To determine the magnitude of the energy change, we must first convert the amount of Br 2 to moles.
As with melting, the energy in boiling goes exclusively to changing the phase of a substance; it does not go into changing the temperature of a substance.
So boiling is also an isothermal process. Only when all of a substance has boiled does any additional energy go to changing its temperature. What happens when a liquid becomes a gas? We have already established that a liquid is composed of particles in contact with each other. When a liquid becomes a gas, the particles separate from each other, with each particle going its own way in space.
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