Answer: D) By decreasing the activation energy of a reaction
A catalyst is a substance that speed up the rate of chemical reaction without affecting the product of the reaction. They only affect the rate of reaction not the yield of reaction.
Catalyst provide an alternative reaction pathway that has lower activation energy than that of uncatalysed reaction. It increases the frequency of collision and because of these greater collision which lowers the activation energy of the reaction.
The solid inner core is made of mainly iron crystals with small amounts of nickel and heavier elements such as gold and platinum. The liquid outer core is a nickel iron alloy with small amounts of heavier elements.
The answer is...
<u>Closed</u> ecosystems do not experience any new input or output of energy and/or material.
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Mouth or nose. Then goes into your trachea and into your lungs