Answer:
Chemical Change
Explanation:
It became white and became solid which makes it a chemical change.
If the core were to cool completely, the planet would grow cold and dead. It also would get a little dark: Power utilities pull radiant heat from Earth's crust and use it to heat water, the steam from which powers turbines to create electricity.Cooling also could cost us the magnetic shield around the planet created by heat from the core. This shield protects Earth from cosmic radiation. The shield is created by a convection process caused by constantly moving iron. Like the planet itself, Earth's core is constantly spinning. Some scientists think it's moving even faster than the rest of the planet. The friction converts kinetic energy into electrical and magnetic energy that forms the field, which deflects harmful, charged particles emanating from the sun toward the north and south poles. Your welcome :)
Explanation :
(a) 
This reaction is combustion reaction in which an oxygen react with a molecule to give its corresponding oxides ans water molecule.
(b) 
This reaction is a redox reaction or oxidation-reduction reaction in which sulfur get oxidized and oxygen get reduced.
(c) 
This reaction is a combination reaction in which the two reactants molecule combine to form a large molecule or product.
(d) 
This reaction is a decomposition reaction in which a large molecule or reactant decomposes to give two or more molecule or products.
(e) 
This reaction is a double displacement reaction in which the cation of two reactants molecule exchange their places to give two different products.
(f) 
This reaction is a combination reaction in which the two reactants combine to form a large molecule or product.
(g) 
This reaction is a double displacement reaction in which the cation of two reactants molecule exchange their places to give two different products.
(h) 
This reaction is combustion reaction in which a hydrocarbon react with an oxygen to give carbon dioxide and water as a products.
Very low gives free energy