Kinetic and Potential Energy on the Nanoscale

Kinetic Energy on the Nanoscale thermal energy Baseball Looking at a tiny piece within the baseball.

Potential Energy on the Nanoscale Case 1 Case 2 Different position means different potential energy

Temperature Cool Block Warm Block Figure 3. Two blocks touching. One is initially warm and one is initially cool.

Temperature measure of average kinetic energy of KMT particles

Temperature Fahrenheit 212 o F 32 o F Celsius 100 o C 0oC0oC Kelvin 373 K 273 K Figure 5. The three common temperature scales (Fahrenheit, Celsius, and Kelvin). The degree markings on thermometers are based on the freezing and boiling points of water (depicted here for each scale). o F = (9/5 × o C) + 32 o C = 5/9 × ( o F – 32) o F = (9/5 × o C) + 32 o C = 5/9 × ( o F – 32)

Temperature Cool Block Warm Block Figure 3. Two blocks touching. One is initially warm and one is initially cool. Energy is transferred from one block to the other – there is a heat flow, or heat is transferred

Warming/Cooling (Transferring Heat) Do all substances change their temperature same way? Do all substances absorb same amount of heat to appear “hot”?

Warming/Cooling (Transferring Heat) For different amounts of a particular substance (iron for example), will the same amount of heat cause the substance to feel hot? Is the same amount of heat needed to cause the same temperature change for different masses (of same substance)?

Specific Heat Capacity Amount of heat needed to raise the temp of 1 gram of material by 1 o C

Using Heat Capacity Heat transferred = q = C s * m *  T Determine the amount of heat transferred for 15.0 g of water if the temperature changes from 20.0 o C to 50.0 o C.

Using Heat Capacity If the same amount of heat transferred to water in the last problem was transferred instead to a 15.0 g sample of iron that was at 20 o C (specific heat capacity=0.449 J/g o C), what change would occur for the iron? –Ans: The iron would increase its temperature by 281 o C.

Phase Changes If we continue to add heat to our water sample, what happens? Temp will continue to increase When we reach 100 o C, what happens? –Water boils

Phase Changes Description of Phase Change Name of Change Solid  LiquidMelting or Fusion Liquid  SolidFreezing Liquid  GasVaporization Gas  LiqCondensation Solid  Gas (directly without changing to liquid first, dry ice does this) Sublimation Gas  Solid (directly without changing to liquid first) Deposition

Ice Bath Activity Was there a temperature change? Was there a flow of heat? Was energy conserved? How can there be a flow of heat, but no temperature change?

Phase Changes temperature of substance undergoing phase change does not change during the phase change

Latent Heat of Fusion Heat required to melt 1 gram of a material 333J/g for water (ice) How much heat would be needed to melt 20 g of ice?

Latent Heat of Vaporization Heat required to vaporize 1 gram of a material 2260 J/g for water (ice) How much heat would be needed to vaporize 20 g of ice?

Heat transfers One of two things may occur –Temperature change –Phase change –HANDLE EACH DIFFERENTLY! –Each may occur in stages or steps!

Changes with Heat Amount of Heat Transferred Temperature ( o C) Heating Ice

Heat transfers You may see one of two things occur –Temperature change –Phase change –HANDLE EACH DIFFERENTLY! –Each may occur in stages or steps!

General Heat Transfers If a 300 g sample of water were at 22.4 o C, what transfer of heat would occur to make all of this sample become ice? Note: for water  H vap = 2260 J/g;  H fus = 333 J/g C s (wtr) = J/(g o C); C s (ice) = 2.06 J/(g o C)

Applying our understanding of heat – including conservation of energy If a 10 g block of iron that was at 90 o C was added to an insulated container of water that was at 25 o C, what would happen? Once the temperature of the water stopped rising, the water and the block were at 30 o C. How much water was present? (Note the specific heat capacity of iron is J/(g o C) and that for water is J/(g o C).)

Water and Cold Objects Activity Was there a temperature change? Was there a flow of heat? From where to where? If object is the system, was it an endo- or an exothermic change? Was it the same heat flow for each object?

Water and Cold Objects Activity Role of heat capacity! NOW, ICE…..