Thermo

THERMOCHEMISTRY

TOPIC 1

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LEARNING OUTCOMES

At the end of this topic, you should be able to: 1. Explain the concept of chemical energy, potential energy, work, heat, heat capacity, specific heat capacity and Hess Law 2. Draw energy profiles diagram of exothermic and endothermic reactions. 3. Distinguish the differences between the reaction in a simple and bomb calorimeter 4. Calculate the heat of reaction, enthalpy of combustion and enthalpy of formation.

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WORK

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is done to achieve motion against an opposing force; Work = force x distance

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WORK

Examples: 1.The process of raising a weight against the pull of gravity 2. A chemical reaction that drives an electric current through a resistance

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ENERGY

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Is the capacity of a system to do work

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work is done on an isolated system (for example by compressing a gas),

the system does work (when the piston moves out)

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ENERGY

KINETIC ENERGY

POTENTIAL ENERGY

CHEMICAL ENERGY

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HEAT

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Energy has been transferred as heat when the energy of a system changes as a result of a temperature difference between the system and its surroundings

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Boundaries: - diathermic; - adiabatic.

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SYSTEM

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TYPES OF SYSTEM

SYSTEM

OPEN SYSTEM

CLOSED SYSTEM

ISOLATED SYSTEM

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OPEN SYSTEM

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CLOSED SYSTEM

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ISOLATED SYSTEM

INSULATOR

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STATE OF A SYSTEM

DESCRIBING THE CONDITION OF THE SYSTEM BY GIVING THE VALUES OF A SUFFICIENT SET OF NUMERICAL VARIABLES.

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STATE FUNCTION

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A state function (state variable) is a property of a system that depends only on the current state (condition) of the system, not on the way in which the system acquired that state (independent of path). Example:

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EXOTHERMIC REACTIONS

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Any reaction that releases energy as heat into its surroundings. Heat flow : System →...