You did work against friction, where did the energy go? Thermal Energy

Thermal Energy Thermal Energy: The total internal Energy Internal Energy: The sum of the kinetic and potential energies of the internal motion of particles that make up an object.

What is Heat? Thermal Equilibrium Heat is energy in transfer from an object of higher temperature to one of lower temperature. The quantity of energy transfer from one object to another is because of a difference in temperature. Heat Flow Cold Warm Hot Thermal Equilibrium

Change of Phase of State States of matter Solid Liquid Gas What happens to the temperature when matter is changing states?

Substances in Phase Transfer 40 32 212 0 100 F C

Phase Change Between A-B: The ice is warming to 0oC Between B-C: Thermal energy melts the ice at 0oC Between C-D: The water is warm to 100oC Between D-E: The water boils and changes to vapor at 100oC After E: The temperature of the vapor increases A B C E D

Thermal Energy Transfer Conduction: Transfer of Kinetic Energy by contact Convection: Heat transfer by the motion of a fluid (e.g. air) Radiation: Electromagnetic waves carry energy Note: Conduction and Convection require matter

Conduction Conduction is the transfer of heat through molecular collisions. This form of heat transfer best occurs in solids where molecules are closely packed. Materials that conduct heat well are called conductors. (Eg. metals such as copper and iron) Magnification

Convection Convection is the transfer of heat though moving fluids. A fluid is any substance that flows, which includes all liquids and gases. Examples include convection ovens and cloud formation. Convection ?

Radiation (not radioactivity) Radiation is the transfer of heat via electromagnetic waves. These waves include visible light, but are mostly infrared. No matter is required for this type of heat transfer. Examples include the sun’s heat and warmth felt from a flame. Open Space Radiation ?

Heat Transfer Question Consider a camp fire burning vigorously. How is heat normally transferred while warming its viewers? Radiation How is heat transferred when you put a hand in the smoke? Convection How is heat transferred to a stick when it is placed in the hot coals? Conduction Some situations involve multiple heat transfer types like this.

Specific Heat Heat: The energy that flows as a result of a difference in temperature Q: The symbol for heat. Measured in Joules (J) C: the symbol for Specific Heat. The amount of energy needed to raise a unit of mass one temperature unit. (J/kg K)

Heat gained Q: Heat m: mass ΔT: Change in Temperature

Sample Heat Problem How much heat is required to raise the temperature of a 2.4kg gold ingot (c = 129J/kgK) from 23°C to 45°C? Light 2.4kg

Calorimerty Calorimeter: A device used to measure changes in thermal energy. Calorimerty depends on the conservation of energy. Qgained + Qlost = Zero

Calorimerty Example #1 A .4kg block of zinc @115°C is placed in .5kg of water @15°C. Find the final temperature.

Heat of fusion Example #1 If 5,000J is added to ice at 0oC, how much ice is melted? Q=mHf Q=mHv Water Hf=3.34x105J/kg Water Hv=2.26x106J/kg Specific Heat Phase Change

Calorimerty Example example #2 A .1kg block of brass @90°C is placed in .2kg of water @20°C. Find the final temperature.

Heat of fusion example #2 How much heat must be transferred to 100g of ice at 00C unit the ice melts and the temperature of the resulting water rises to 200C? Water Hf=3.34x105J/kg

Heat Transfer Example 1 A 0.40kg block of iron is heated from 295K to 325K. How much heat is absorbed by the iron? C=450J/kg K