PHY 317K 1st Edition Lecture 21 Outline of Last Lecture I. Explain why different substances have different specific heat capacitiesII. Solve problems involving specific heat capacitiesIII. Describe the solid, liquid, and gaseous statesOutline of Current Lecture I. Describe and explain the process of phase changes in terms of molecular behaviorII. Explain in terms of molecular behavior why temperature does not change during a phase changeIII. Specific Latent HeatIV. Solve problems involving specific latent heatsV. Identify factors that affect evaporation rate.Current LectureDescribe and explain the process of phase changes in terms of molecular behavior.- When a material goes from solid to liquid or liquid to gas it is called a phase change.- As a solid is heated, energy is added to the material, the solid will eventually melt as the particles collect to much energy to stay in the tight lattice pattern.- If the resulting liquid continues to be heated then particles will eventually “fly free” and form a loosely associated gas.Explain in terms of molecular behavior why temperature does not change during a phase change- When a material undergoes a phase change energy has to be continuously added to the material to continue the phase change, but the temperature of the material does not change. - When a material goes from a solid to a liquid the distance between particles does not increase significantly. - The energy goes into breaking the intermolecular or interparticle forces. - As a material goes from a liquid to a gas (vaporized), again the temperature does not increase the energy is going into further disassociating the particles or adding potential energy to the particles. - The further particles are away from each other the greater potential energy they have, just like with gravitational forces the further to bodies are away the more potential energy they have.Define specific latent heat- Specific latent heat is defined as the energy or heat per unit mass required for a materialto undergo a phase change.- Specific latent heat of fusion is defined as the energy per unit mass required to melt a material:- Specific latent heat of vaporization is defined as the energy per unit mass required to vaporize or convert a material from liquid to gas:- The particles in a liquid are nearly as dense as in a solid, but the particles in a gas are much less dense than in a liquid or solid. - Thus the specific latent heat of vaporization is usually far greater than the specific latent heat of fusion.- It should be noted that the energy required to melt or vaporize a material is then released if the material is allowed to cool and return to solid (freezing or solidification) or liquid (condensation) form.Solve problems involving specific latent heats- In order to measure the specific latent heat you must be able to accurately measure the amount of heat going into or out of a material. - The mass of the material must also be accurately measured, but that’s not too tough.- As energy is added to the material the temperature will become constant as the materialstarts to undergo a phase change. - At this point the amount of energy being transferred to the material needs to be recorded or tracked until the temperature starts to change again (the phase change is finished).- It is also possible under specific conditions for a material to straight from solid to gas. This is called sublimation. - Frozen carbon dioxide will sublime at standard temperature and pressure. - There is a latent heat associated with this as well, it’s called specific latent heat of sublimation, surprise surprise.Identify factors that affect evaporation rate.- If a water is left in an open container at room temperature it will slowly evaporate, yet it’s boiling point is well above room temperature… - At room temperature most of the water molecules do not have enough energy to disassociate and vaporize, but some do. - The molecules that have sufficient energy evaporate and take their energy with them.- This has the effect of lowering the average energy per molecule of the water, which reduces the temperature of the water. - This is called evaporative cooling. This is why you sweat when you exercise. As the sweat evaporates off your skin your body is cooled.- There are several factors that affect the evaporation rate. Increasing the temperature of the liquid will increase the evaporation rate. - Increasing the exposed surface area will also increase the evaporation rate. A decrease in atmospheric pressure above the liquid will reduce the evaporation