Answer: When you mix sand and water there are no reactions. The sand sits at the bottom of the water because the sand is heavier than the water is.
Answer:
which one is it 9 42 or 12?
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.
Answer:
chemical composition,cells, tissues,organs,organ systems,organism.
Answer:
A. It allows two populations to evolve separately.
Explanation:
Geographic isolation is theorized to have catalyzed the formation of new species. Let’s say groups A and B of a bird species get separated by something, and they can’t cross between to interbreed or exchange alleles.
We describe this as no gene flow, which is the opposite of choices C and D. Because of this, they may diverge if given enough time due to the difference in environmental pressures, because they’re now in different environments.
B is incorrect because it doesn’t apply.
