Download energy-and-entropy-introduction

Metabolism is the sum of all chemical
reactions in an organism.
Energy is the ability to do work
How do these work together?
Metabolism in a nutshell
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WOW There is a lot going on!
What is energy
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Energy
Energy is used anytime work is performed
• Climb a mountain
• Car travels down the road
• Link amino acids together
• Pump sucrose across a membrane
Many forms…
• Chemical
• Electrical
• Mechanical
• Light
• Thermal
Regardless of the form, energy exists in one of two states…
• Kinetic Energy
• Stored Energy- Potential energy
Kinetic vs. Potential Energy
Kinetic Energy
• energy of motion
• Performs work by making things move
Potential Energy
• stored energy
• chemical potential/gravitational energy
The First Law of Thermodynamics
The total amount of energy in any closed system is constant. Energy cannot be
created or destroyed; it can only be converted from one form to another. If a
physical system gains an amount of energy, another physical system must
experience a loss of energy of the same amount.
BOND ENERGY
• A measure of the strength or stability of the covalent bond
• Measured in KJ/mol (equal to amount of energy absorbed per mole when the
bond between atoms is broken(energy is needed to be put into the breaking of
the bonds))
Important
• Energy is absorbed by the bonds as energy is put in to break them and energy is released
Question • How will this affect the net amount of energy absorbed or released in the overall reaction?
Endothermic vs. Exothermic
Energy Diagrams…
• the y-axis indicates the level of potential energy for the reactants before the reaction and the
products after the reaction has occurred
• If energy is released, the reaction is EXOTHERMIC
• If energy is absorbed, the reaction is ENDOTHERMIC
Bond energy and Potential energy have an inverse relationship
• The weaker the bond, the higher the potential energy
• The stronger the bond, the lower the potential energy
Enthalpy (∆ H)
The measure of the energy of a system usually measured using
heat released or absorbed by a system overall.
This is calculated by using the following formula;
∆ H total = ∆ H final - ∆ H initial
Exothermic Reaction have a - ∆ H
Endothermic Reactions have a + ∆ H
The second Law of Thermodynamics
In every energy transfer or conversion, some of the useful energy in the system becomes unusable and
increases the entropy of the universe.
So what is Entropy??
Entropy is a measurement of the disorder in a system.
CHAOS…..
In chemical reactions entropy actually increases when
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Solids react to form liquids or gases
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Liquids react to form gases
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The total number of product molecules is greater than the total number of reactant molecules
There is energy expended to maintain the living structures in all living things. This allows order to be
established even when there is disorder (entropy).
Spontaneous change is a change that will, once begun, continue on its own under a given set of conditions and
it will not require a continuous supply of energy.
So a non spontaneous reaction is one that needs continual energy input to continue.
Gibbs Free Energy: What is this?? What is the
equation?
Define exergonic and endergonic reactions.
P.137-138
Compare and contrast
Kinetic and Potential energy
Exothermic and Endothermic reactions