Expert: John Locke - 9/20/2007

Question
if its ok to ask more than 1...
(1)which of the following will result in a chemical change?
a.melting ice to obtain water
b.evaporating alcohol into vapor
c.drying wood in a shed
d.burning coal in a furnace

(2)a salt is obtained as a reaction between?
a.a nonmetal and a metal
b.a base and water
c.an acid and oxygen
d.a base and an acid

Answer
Dear Sarah,

It's certainly fine to ask more than one question on AllExperts, but many of us do prefer that you simply not request answers to homework questions. That said, let me suggest some things that should help you narrow down the answer choices.

Let's consider the first question. Each answer choice includes two substances that undergo some kind of change; it could be physical or chemical in nature. A chemical change occurs only if the molecules that make up the substances change their structure. Look at each answer choice and consider this: does the chemical structure differ between the starting and ending substances? More specifically, what chemical substance makes ice? What chemical substance makes water? Is there a chemical difference between liquid alcohol and alcohol vapor? What's being lost from the wood when it is dried? What change occurs when wood is burned?

On to question 2. A salt is a combination of a positively charged ion (cation) and a negatively charged ion (anion). One of the most common examples is sodium chloride, which chemically consists of a sodium cation and chloride anion: Na+ and Cl-. You can obtain sodium chloride by reacting sodium hydroxide (NaOH) and hydrogen chloride (HCl):

NaOH + HCl --> NaCl + water

Find out what NaOH and HCl are, chemically, and you'll have your answer: the kind of reaction that produces the salt NaCl is the same kind of reaction that produces salts, generally.