Ib Environmental Systems & Societies Topic 1: Systems & Models Thermodynamics Topic 1: Systems & Models Thermodynamics

1.1.4: Describe how the 1st & 2nd laws of thermodynamics are relevant to environmental systems The laws of thermodynamics describe the transport of heat & work in thermodynamic processes The 1st law of thermodynamics: Energy cannot be created nor destroyed. It can only change form. This is the statement of conservation of energy The laws of thermodynamics describe the transport of heat & work in thermodynamic processes The 1st law of thermodynamics: Energy cannot be created nor destroyed. It can only change form. This is the statement of conservation of energy

1.1.4: Describe how the 1st & 2nd laws of thermodynamics are relevant to environmental systems In any process where work is done, there has been an energy transformation With no energy transformation there is no way to perform any type of work All systems carry out work, therefore all systems need to transform energy to work and be functional In any process where work is done, there has been an energy transformation With no energy transformation there is no way to perform any type of work All systems carry out work, therefore all systems need to transform energy to work and be functional

First Law of Thermodynamics ENERGY 2 PROCESS ENERGY 1 (WORK) ENERGY 3 12

Photosynthesis and the First Law of Thermodynamics Heat Energy Light Energy Chemical Energy Photosynthesis 18

Photosynthesis: an example of the First Law of Thermodynamics: Energy Transformation 17

1.1.4: Describe how the 1st & 2nd laws of thermodynamics are relevant to environmental systems The laws of thermodynamics describe the transport of heat & work in thermodynamic processes The 2nd law of thermodynamics: In any isolated system entropy tends to increase spontaneously This means that energy and materials go from a concentrated to a dispersed form and the system becomes increasingly disordered Therefore, the capacity to do work diminishes The laws of thermodynamics describe the transport of heat & work in thermodynamic processes The 2nd law of thermodynamics: In any isolated system entropy tends to increase spontaneously This means that energy and materials go from a concentrated to a dispersed form and the system becomes increasingly disordered Therefore, the capacity to do work diminishes

1.1.4: Describe how the 1st & 2nd laws of thermodynamics are relevant to environmental systems Entropy: the measure of disorder in a system Life, in any of its forms or levels of organization, is the continuous fight against entropy (disorder). In order to fight against disorder and keep order, organization and functionality, living organisms must use and transform energy to obtain the form of energy most needed. Living organisms use energy continuously to keep all systems working properly. If something is not working properly, organisms must make adjustments. This is done by negative feedback mechanisms. Entropy: the measure of disorder in a system Life, in any of its forms or levels of organization, is the continuous fight against entropy (disorder). In order to fight against disorder and keep order, organization and functionality, living organisms must use and transform energy to obtain the form of energy most needed. Living organisms use energy continuously to keep all systems working properly. If something is not working properly, organisms must make adjustments. This is done by negative feedback mechanisms.

Life & Entropy Entropy Life Energy

Life & Entropy In any spontaneous process the energy transformation is not 100 % efficient, part of it is lost (dissipated) as heat which, can not be used to do work (within the system) to fight against entropy.

Life & Entropy In fact, for most ecosystems, processes average only 10% efficiency (10% Principle), this means that for every energy passage (transformation) 90% is lost in the form of heat energy, only 10% passes to the next element in the system.

Life & Entropy As energy is transformed or passed along longer chains, less and less energy reaches the end. Therefore, elements at the end of the chain must be more efficient because they must operate with a very limited amount of energy.

Life & Entropy In ecological systems, this problem is solved by reducing the number of individuals in higher trophic levels.

Combustion & Cell Respiration: two examples that illustrate the 1st and the 2nd laws of Thermodynamics Heat Energy ATP Chemical Energy (petrol) Chemical Energy (sugar) PROCESS Combustion 20 J PROCESS Cell Respiration 40 J 100 J 80 J 60 J 22

The Second Law of Thermodynamics in numbers: The 10% Law For most ecological process, theamount of energy that is passed from one trophic level to the next is on average 10%. Heat Heat Heat 900 J 90 J 9 J Energy 1 Process 1 Process 2 Process J 100 J 10 J 1 J J = Joule SI Unit of Energy 1kJ = 1 Kilo Joule = 1000 Joules 23