Unit 7 Kinetics and Thermodynamics Cartoon courtesy of

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Unit 7: Kinetics and Thermodynamics Cartoon courtesy of Nearing. Zero. net

Unit 7: Kinetics and Thermodynamics Cartoon courtesy of Nearing. Zero. net

Heat is the energy that is transferred from one object to another because of

Heat is the energy that is transferred from one object to another because of a temperature difference. The direction of heat transfer is always from a hotter object to a colder object. Thermal equilibrium is reached when two or more objects in contact with one another reach the same temperature.

Heat (Enthalpy) Change The amount of heat energy released or absorbed during a process.

Heat (Enthalpy) Change The amount of heat energy released or absorbed during a process. Endothermic: Processes in which energy is absorbed as it proceeds, and surroundings become colder Exothermic: Processes in which energy is released as it proceeds, and surroundings become warmer

You have water at 25°C. You dissolve ammonium acetate, NH 4 C 2 H

You have water at 25°C. You dissolve ammonium acetate, NH 4 C 2 H 4 O 2, in the water and find the temperature decreases to 15°C. Is T positive or negative? Is heat energy transferring from the solution to the environment or from the environment to the solution? Is the process an exothermic or endothermic process?

System: The chunk of the universe being studied (i. e. , a water molecule,

System: The chunk of the universe being studied (i. e. , a water molecule, a beaker of solution, a campfire). Surroundings: Everything “outside” the system.

Heat describes the process of energy transfer. Heat is not a “thing” (a noun).

Heat describes the process of energy transfer. Heat is not a “thing” (a noun). Energy is a measurement of the capacity of a system to do work or to transfer heat. Internal energy is associated with the degree of motion of atoms. Heat transfer changes the internal energy of a system.

Units for Measuring Heat The Joule is the SI system unit for measuring heat:

Units for Measuring Heat The Joule is the SI system unit for measuring heat: The calorie is the heat required to raise the temperature of 1 gram of water by 1 Celsius degree

A Bomb Calorimeter

A Bomb Calorimeter

A Cheaper Calorimeter

A Cheaper Calorimeter

Calorimetry is the measurement of the amount of heat transferred. The temperature rise of

Calorimetry is the measurement of the amount of heat transferred. The temperature rise of water is a measure of the amount of heat transferred from a chemical change such as a fire.

Calorie: The amount of heat needed to raise the temperature of one gram of

Calorie: The amount of heat needed to raise the temperature of one gram of water by one degree Celsius. Specific heat capacity of water is the conversion factor between calories, grams, and temperature change. For water, the conversion factor is 1 calorie/1 gram – 1°C.

Specific Heat The amount of heat required to raise the temperature of one gram

Specific Heat The amount of heat required to raise the temperature of one gram of substance by one degree Celsius.

Calculations Involving Specific Heat OR cp = Specific Heat q = Heat lost or

Calculations Involving Specific Heat OR cp = Specific Heat q = Heat lost or gained T = Temperature change m = Mass

Table of Specific Heats

Table of Specific Heats

Temperature is a measure of the average motion, or kinetic energy, of the atoms

Temperature is a measure of the average motion, or kinetic energy, of the atoms and molecules in a substance. Heat is a measure of the total motion of all the atoms and molecules in a system. More heat is required to raise the temperature as the mass of the substances in the system is increased. The heat required is also specific to the substances, and is called the specific heat. • Latent heat is the heat associated with a phase change and is measured in cal/g.

Latent Heat of Phase Change Molar Heat of Fusion The energy that must be

Latent Heat of Phase Change Molar Heat of Fusion The energy that must be absorbed in order to convert one mole of solid to liquid at its melting point. Molar Heat of Solidification The energy that must be removed in order to convert one mole of liquid to solid at its freezing point.

Latent Heat of Phase Change #2 Molar Heat of Vaporization The energy that must

Latent Heat of Phase Change #2 Molar Heat of Vaporization The energy that must be absorbed in order to convert one mole of liquid to gas at its boiling point. Molar Heat of Condensation The energy that must be removed in order to convert one mole of gas to liquid at its condensation point.

Latent Heat – Sample Problem: The molar heat of fusion of water is 6.

Latent Heat – Sample Problem: The molar heat of fusion of water is 6. 009 k. J/mol. How much energy is needed to convert 60 grams of ice at 0 C to liquid water at 0 C? Mass of ice Molar Mass of water Heat of fusion

Heat of Solution The Heat of Solution is the amount of heat energy absorbed

Heat of Solution The Heat of Solution is the amount of heat energy absorbed (endothermic) or released (exothermic) when a specific amount of solute dissolves in a solvent. Substance Heat of Solution (k. J/mol) Na. OH -44. 51 NH 4 NO 3 +25. 69 KNO 3 +34. 89 HCl -74. 84