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6.3 The Laws of Thermodynamics
If the reaction is catalyzed, the activation energy is lower.
The diagram's horizontal axis shows the sequence of events.
Everything outside of the system is relevant to a particular case of energy transfer.
When heating a pot of water on the stove, the system includes the stove, the pot, and the water.
There are two types of systems.
Energy can be transferred between the system and its surroundings by an open system.
The system is open because it can lose heat.
A closed system can't transfer energy to its surroundings.
The organisms are open.
They consume energystoring molecule and release energy to the environment by doing work.
Energy is subject to the laws of physics.
The laws of the universe govern the transfer of energy.
The total amount of energy is constant.
There has always been the same amount of energy in the universe.
The first law of thermodynamics states that energy can be transferred from place to place, but it can't be created or destroyed.
The transfers and transformations of energy happen all the time.
Light bulbs produce light energy.
Natural gas is transformed into heat energy by gas stoves.
Plants convert sunlight energy into chemical energy that is stored within organic molecules.
The challenge for all living organisms is to obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work.
Living cells are able to meet this challenge.
The energy stored within sugars and fats is converted into energy by cellular chemical reactions.
It is easy to do work with the energy in the ATP molecule.
There are two examples of energy being transferred from one system to another.
Humans can convert the chemical energy in food into the movement of a bicycle.
Plants can convert light energy from the sun into chemical energy.
The primary tasks of a living cell may seem simple.
The second law of thermodynamics explains why these tasks are harder than they appear.
All of the energy transfers and transformations in the universe are not completely efficient.
Some amount of energy is lost in a form that is not usable.
This form is usually heat energy.
When an airplane flies through the air, it loses some of its heat energy because of the surrounding air.
The air molecule speed is temporarily increased by this friction.
During cellular reactions, some energy is lost as heat energy.
Warm-blooded creatures like us benefit from this because heat energy helps maintain our body temperature.
Some energy is lost in an unusable form, so no energy transfer is completely efficient.
Order and disorder are important concepts in physical systems.
The more energy a system loses to its surroundings, the more random it is.
There is high disorder and low energy.
The room would become messy if no work was put into it.
It would be in a state of high entropy.
In order to bring the room back to a state of order, energy must be put into the system in the form of the student doing work and putting everything away.
This state is not very good.
A car or house needs to be kept in an ordered state by constantly being maintained.
Left alone, a house's or car's entropy gradually increases through rust and degradation.
Chemical reactions have varying amounts of entropy as well.
As chemical reactions reach a state of equilibrium, the entropy increases, and as the molecule diffuses and spread out, the entropy also increases.
An experiment can be set up to understand how energy transfers work.
Take a block of ice.
The water has a high structural order because it is in solid form.
The molecule can't move very much because they are in a fixed position.
The ice's temperature is below freezing.
The system's entropy is low.
The ice should be allowed to melt at room temperature.
Living things are highly ordered, requiring constant energy input to maintain themselves in a state of low entropy.
Living systems lose some usable energy when they take in energy-storing molecules and transform them through chemical reactions.
Waste and by-products are not useful energy sources.
The system's surroundings are increased by this process.
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