Chemical Cells And Fuel Cells C
Overzicht
Somewhere in the room you are sitting in there is almost certainly a small sealed cylinder that is quietly eating itself. A cell in a torch, a remote control or a smoke alarm works by letting one metal corrode on purpose, in a container built so that the electrons released have nowhere to go except the long way round, through your circuit. That is the whole trick of a chemical cell: take a reaction that would otherwise waste its energy as heat, and force the electrons to do a job on their way from one reactant to the other.
It also explains the one thing everybody knows about batteries, which is that they go flat. The reactants are sealed inside, there is a fixed amount of them, and when they run out the voltage collapses. This lesson takes that limit seriously and then shows you the engineering answer to it: a cell you never charge and never throw away, because you pipe the reactants in from outside as fast as it uses them. Hydrogen goes in, air goes in, electricity comes out, and the exhaust pipe drips water.
Doelstellingen
- A chemical cell produces a potential difference until the reactants are used up.
- Fuel cells produce electricity through the reaction of a fuel with oxygen. Hydrogen-oxygen fuel cells use hydrogen as their fuel, and are useful in cars and spacecraft. Water is the only waste product from a hydrogen-oxygen fuel cell, so they cause less pollution when in use. Students should be able to compare the advantages and disadvantages of the combustion of hydrogen with the use of hydrogen fuel cells from information that is provided. Students should know and understand the benefits and disadvantages of hydrogen fuel in terms of: storage and use; products of combustion. Knowledge of the details of the reactions in fuel cells is not required.
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- A simple chemical cell is made from two metal strips dipping into an electrolyte. Which change would produce the largest potential difference? A. Using two strips of the same metal B. Using two metals that are close together in the reactivity series C. Using two metals that are far apart in the reactivity series D. Using larger strips of the same two metals Answer: C
- Why does a non-rechargeable chemical cell eventually stop producing a potential difference? A. The electrons in the wire are used up. B. The reactants inside the cell are used up. C. The electrolyte cools down. D. The electrodes become the same metal. Answer: B
- Which substance is the only product of the reaction in a hydrogen-oxygen fuel cell? A. Carbon dioxide B. Hydrogen peroxide C. Water D. Oxides of nitrogen Answer: C
- Which statement explains the main difference between a fuel cell and an ordinary chemical cell? A. A fuel cell contains no electrolyte. B. A fuel cell has electrodes made of the same metal. C. A fuel cell has its reactants supplied continuously from outside. D. A fuel cell produces heat rather than a potential difference. Answer: C
- Which of these is a disadvantage of using hydrogen as a fuel in a car? A. Burning it produces carbon dioxide. B. It is difficult to store because it is a gas of very low density at ordinary temperatures. C. It cannot be made from water. D. It releases no energy when it reacts with oxygen. Answer: B
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