Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
The scientific method is the "process of experimentation" for your hypothesis. There are five steps in the scientific method they consist of: conduct research, form hypothesis, test hypothesis, record data, draw conclusion.
Hope this helps!
Answer: The correct answer is C: decreased use of fossil fuels.
Explanation: The burning of fossil fuels causes the release of CO2 and other harmful substances into the atmosphere. Fossil fuels are fuels that are burnt by power plants and such to generate power.
Answer:
1. B
2. A
3. C
4. A
5. A
Explanation:
A nursery bed can be defined as a specially prepared temporary plot of land or garden which serves as a home for raising seedlings (young plants) prior to planting them in the main location (area). Thus, when older trees in the environment or surrounding dies or are cut-off, these younger plants (trees) propagated in the nursery bed are transferred to replace them.
<em>Some of the criteria or requirements for setting up a nursery bed are;</em>
1. Shed: this is one structure essential in propagating young trees.
2. Location/Site: a place near a source of water should be chosen because water is essential for plant growth and coolness from extreme heat caused by the sun.
3. Storage place for tools and equipment: it is important to have a complete set of tools or their substitute to be able to carry out all nursery activities properly.
4. Boxes, pots, and plots for germinating seeds: there are three places to germinate seeds, young plants, and young trees. Pots are used for germinating young trees while boxes and plots are used for raising seedlings.
5. Soil type: different plants need different types of soil. These includes clay, loamy and sandy soil.
