When Sodium is dropped into Bromine, they react violently producing heat and light and a stable crystal structure (Sodium Bromide).
The chemical equation is written Na+ Br = NaBr.

Answer the following question about this reaction.

A. Is this reaction exothermic or endothermic? Explain how you know.

b. What are the products?

C. What are the reactants?

D. Which of the four indicators let you know that a chemical reaction took place?

with this one i know the answer in craters one reason i looked it up and i learned about it there is my evidence

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.