Answer:
Chemical change
Explanation:
The rusting of iron/a nail is a chemical change
Iron (Fe) and Oxygen (O) combine to create the compound Iron Oxide (Fe2O3), which is rust.
<span>polyunsaturated!!! Hope this helps mark this the brainliest!</span>
Answer: 
Explanation: According to law of conservation of mass, mass can neither be created nor be destroyed.
Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
This is an example of combustion reaction in which hydrocarbon reacts with oxygen to form carbon dioxide and water. This is an exothermic reaction in which a large amount of heat is liberated, thus water also exists as vapors.

Answer:
metallic bond
Explanation:
Metallic bonding is the type of bonding metal atoms undergo. The bond is formed through the electrostatic attraction between a lattice of positive ions and negative delocalized electrons. The lattice of cations is surrounded by a sea of delocalized electrons.