________ and O2 are pumped through two porous electrodeswhere the half- reactions occur.
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Fuel cells
________ are affected by low temperatures, becoming less efficient.
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fossil fuels
The ________ give out a lot of heat but they cause pollution, with coal the worst culprit, the pollutants in key carbon dioxide which is linked to global warming and other gases that cause acid rain we will look into this later on.
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CO2
No ________ or other polluting gases are formed.
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Hydrogen
________ has a some unique advantages and disadvantages regarding its use as a fuel:
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Nuclear Fuels
________ are not burned.
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exothermic reaction
During a(n) ________, more energy is energy is given out when new bonds are made than the energy taken in to break bonds.
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Uranium 235
________ undergoes decay and gives off heat energy which nuclear power stations harness, (________ is often used.
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fuel
A(n) ________ is a substance which releases energy when burned.
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High pressure tanks
________ are needed to store the oxygen and hydrogen in sufficient amounts.
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Hand warmers
________ used in the wintertime are based on the release of heat from an exothermic reaction.
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silver nitrate
Mixing ________ and sodium chloride solutions gives a white precipitate of silver chloride- and a temperature rise.
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Jets of steam
________ are then used to drive turbines for generating electricity.
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Endothermic reactions
________ take in energy from their surroundings.
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new bonds
More energy is released when ________ are formed than energy required to break the bonds in the reactants.
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symbol ΔH
The ________ (delta H) is used to show the change in heat energy.
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H
________ is the symbol for enthaply, which is a measure of the total heat of reaction of a chemical reaction.
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y axis
The energy of the reactants and products are displayed on the ________ and the reaction pathway (a bit like time) is shown on the x- axis.
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chemical reaction
During a(n) ________ there is always an energy change.
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Reactants
> Products + energy
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This energy is transferred from the chemical energy store of the chemical system to the surroundings and so the energy of the system falls
this means that the energy change is negative
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mixing silver nitrate and sodium chloride solutions gives a white precipitate of silver chloride
and a temperature rise
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Reactants + Energy
> Products
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This energy is transferred to the chemical energy store of the chemical system and so the energy of the system increases
this means the energy change is positive
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The neutralization that occurs takes in heat
so your tongue cools
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Optional
draw the displayed formula in order to identify the type and number of bonds more easily
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Add together all the bond energies for all the bonds in the reactants
this is the ‘energy in
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Add together the bond energies for all the bonds in the products
this is the ‘energy out
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The fossil fuels
coal petroleum (oil) and natural gas (methane) are the main fuels used around the world
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Flashcard (33)