Please help me with this science question

it is less dense than the surrounding mantle

Explanation:

everything has some kind of density. while gases are exponentially less than solids they still have density just as liquids do. magma is a liquid that is less dense than a solid (mantle).

8 carbon atoms forming single bonds with 18 hydrogen atoms; a triple bond exists between the third and fourth carbon atom from the right

explanation:

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.