There are four states of matter, solid, liquid, gas and plasma. Their formation is as when solid is heated it converts into liquid, liquid on heating converts into gases and gases on heating converts into plasma.
Plasma:
Plasma is the fourth state of matter. It is the highest energy state of matter.
Composition:
Plasma is made up of negatively charged and positively charged particles.
Result:
The answer to your question is Plasma.
Answer: The correct option is C ( is very hard and burns cleanly).
Explanation:
COAL is a form of rock that is made up of mostly carbon amongst other elements which includes sulphur, nitrogen, hydrogen and oxygen. There are different types of coal which include:
--> anthracite ( 90% carbon)
--> bituminous coal ( 70-90% carbon)
--> lignite ( 60- 70% carbon) and
--> peat (60 % carbon).
Anthracite is the type of coal that contains the highest carbon content ( 90% carbon). This makes it very hard and is often a times referred to as HARD COAL. Anthracite is a higher quality coal for domestic and open fire heating. This is because it contains less impurities than other type of coal and thereby making it to BURN CLEANLY avoiding atmospheric pollution.
The numbers may be off by a few, if you worked it out, since my periodic table is for AP chemistry. Hope this helps!!!
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As a sidenote, you posted this in Chemistry, when it actually belongs in another topic. Please be sure to post questions only where they belong. Thanks! :)