1.3 Energy and equilibria

Significant ideas:

• The laws of thermodynamics govern the flow of energy in a system and the ability to do work.
• Systems can exist in alternative stable states or as equilibria between which there are tipping points.
• Destabilizing positive feedback mechanisms will drive systems towards these tipping points, whereas stabilizing negative feedback mechanisms will resist such changes.

Imagine an egg rolling off a table and smashing....what happens? Entropy happens!

Revise...

Systems: an assemblage of parts and their relationship forming a functioning entirety or whole

• Open systems: exchanges matter and energy
• Closed systems: exchanges only energy
• Isolated systems: neither matter nor energy and is theoretical

Equilibrium

• Steady-state: in open systems, continuous inputs and outputs of energy and matter, system as a whole remains in a constant state, no long term changes but there may be oscillations in the short term.
• Static: no change over time; when the state of equilibrium is distributed, the system adapts a new equilibrium; can’t occur in living systems
• Stable: the system returns to the previous equilibrium after disturbances
• Unstable: system returns to a new equilibrium after disturbances
• Tipping point: the minimum amount of change within a system that will destabalize it, causing it to reach a new equilibrium or stable state.

Feedback

• Positive: results in a further decrease of output and the system is destabilized and pushed into a new state of equilibrium
• Negative: tends to neutralize or counteract any deviation from an equilibrium and tends to stabilize systems

New ideas....

Laws of thermodynamics

• 1st: energy is neither created nor destroyed, only changes forms. The Law of Conservation of Energy or E=MC²
• 2nd: the entropy of a closed system increases; when energy is transformed into work, some energy is always lost. The system goes from an ordered state into a chaotic state.

Transfers and transformations

Transfers use less energy than transformations and are therefore more energy efficient.

Transfers:

• refers to processes that move through a system and produce a change in location
• The movement of material through living organism.
• Movement of material in non-living process.
• The movement of energy

E.g.....

Transformations

• involve chemical changes or changes in states
• Matter to matter e.g.
• Energy to energy e.g.
• Matter to energy e.g.
• Energy to matter e.g.

Efficiency = useful energy, the work or output produced by a process / energy consumed.

Efficiency = useful output / input

x100 if you want to express the efficiency as a %

Task:

Design an investigation to investigate the Thermodynamics of Food (IA) practice

When organisms consume food, their bodies convert the stored energy, known as Calories, to chemical energy, thereby allowing them to do work. A calorie is the amount of heat (energy) required to raise the temperature of 1 gram (g) of water 1 degree Celsius (°C).

You can determine energy content of food by burning a portion of it and capturing the heat released to a known amount of water. This technique is called calorimetry. The energy content of the food is the amount of heat produced by the combustion of 1 gram of a substance.

So multiplying the rise in temperature of water by the mass of the water and then by 4.2 gives the number of joules of energy that were transferred to the water.

Energy (J/g) = (final temperature – start temperature) x mass of water (g) x 4.2 (J per ^oC)

(Mass of food burned (g)

Write the method of data collection that could be used.

Be systematic and consider:

• equipment
• reliability
• repeat-ability
• validity
• safety/risks