What is a Search Engine?

If you want to find information, what is the first thing you do?

You will probably use your smartphone, tablet, laptop, notebook, netbook, or some other "computer", to connect to the internet and then type your question into a search engine.
You've probably used one of the popular search engines such as google, yahoo or bing, but there are hundreds of search engines to choose from (you can visit http://www.thesearchenginelist.com if you would like a lengthy list of search engines).

A search engine can be a useful tool for helping you find information, as long as you enter an appropriate search term. In other words, if you ask a silly question you will get lots of silly responses (known as garbage in, garbage out, or GIGO).

It is important to realize that a search engine is NOT a person, a search engine can not answer your questions.
A search engine is NOT an encyclopedia, it does not give you specific information related to your question. Search Engines do not write their own pages of information.
A search engine is NOT a dictionary, it can not define a term for you and give you examples of usage. Search engines do not write their own definitions or examples.

So, what is a search engine?
A search is just a computer program that acts like a library catalogue or the index of a book.
Pages on the internet containing information are categorized by the search engine, just like in a library catalogue or the index of a book.
When you type in your search term, or question, the search engine matches your term, or question, as closely as possible to the pages of information on the internet that it has catalogued or indexed.

So what? Who cares?
You should!
In order to successfully use a search engine to find what you want, you need to understand what it is (and what it is not) in order to understand what it can do (and what it can't do).
Let's take a look at some examples.

1. A Search Engine is NOT a Person
a) The term with multiple meanings
Example : mole
Your chemistry teacher will tell you that a mole is defined as 6.02 x 10²³ "things", or as the molecular mass of a substance expressed in grams.
If you type mole into your favourite generic search engine (eg, google, yahoo, bing) you will end up with a list of links to pages of information on the internet about various types of moles including the chemical definition of a mole, the mole as an animal, the mole as skin blemish (moles and freckles), mole as a Mexican sauce.
The search engine is not capable of interpreting your question and putting it into context like a person can.
If you ask your chemistry what a mole is, the chemistry teacher assumes you are talking about a chemical mole.
If you ask your biology teacher what a mole is he or she will probably ask you for more information (what sort of mole do you mean).
If you ask a medical doctor, he/she will probably tell you about skin blemishes.
As a cook about mole, they'll start talking about sauces.
A search engine cannot guess what type of mole you are interested in because a search engine is not a person.

b) "The homework answer"
If you ask a person what a + 2a is if a is equal to 2, they will probably 6, and your maths homework is probably done.
Now, type a + 2a if a is equal to 2 into your favourite search engine. What do you get? You get a list of pages on the internet, probably maths related, which include reference to a, +, and 2a.
The search engine cannot answer your homework question if you treat the search engine like a person.

c) "The homework question"
If you stand in front of someone and ask, "happy?", they will probably assume you are asking them if they are happy and respond to the implied question by saying something, "Yes. I'm happy."
A search engine cannot interpret the question, so a search engine does not know if you asking for a definition of the word happy, or if you are asking it if it is happy, or if you are asking about movies that have happy in the title etc. You can prove this to yourself just by opening up 2 windows with your favourite search engine open in each and typing "happy" into one and "are you happy?" into the other.

d) Spelling Mistakes and Typos
Spelling is important in science, and it can be critical in chemistry.
If you have been asked to find out about ethene, but you type ethane into your search engine, your search engine will list resources dealing with ethane NOT ethene. The search engine does not know you have made a spelling mistake or typo because both ethane and ethene exist.

e) Asking Nonsense
You type nonsense into a search engine's textbox it will provide you with a list of links to resources on the internet that make reference, in some way, to the nonsense you have typed in. A person would know you are asking nonsense, but a search engine is not "intelligent", it can't decide that what you are asking is nonsense.
For example, if you ask a person  how old Jo is if John is Jane's brother they'll tell you this is nonsense, but if you type how old is Jo if John is Jane's brother into the textbox of a search engine, you'll end up with millions of links to pages that reference Jo, John, Jane, brother, old, etc.

2. A Search is NOT an Encyclopedia nor is it a Dictionary
A search engine is not a "resource", it is only a tool.
An encyclopedia is a resource, it provides information that you can use.
In order to find the information you want in the encyclopedia you can use its index, the index is a tool.
Pages on the internet contain information, these pages are the resources.
A search engine is a tool you can use to find the resources.
If you have been asked by your chemistry teacher to find out about quicksilver, and you type "quicksilver" into your favourite search engine, the search engine gives you millions, of links to pages on the web that make reference to quicksilver. In order to get the information you will need to click each link.

There are ways to ensure that you don't put garbage into a search engine, which should reduce the amount of garbage the search engine gives you, but we'll deal with that another day.

Practice Questions
Which of the following questions are most likely to be appropriate search terms or questions (things you could type into a search engine that would result in links to web pages that contain similar sorts of useful information)? Explain your decision in each case.

1. What is the red dot in the diagram?
2. multiplication
3. mathematical multiplication
4. What is induction?
5.  mathematical induction
6. What is the answer to question 4 on page 91?
7. How many moles are in x grams of NaCl?
8. How long does it take to melt ice?
9. What is the chemical composition of ice?
10. What is the chemical composition of solid water?

The examples below are actual search terms that real people have typed into a search engine
In each case, explain why it is NOT an appropriate search term.

1. if the density is 4.70 g/cm3, then calculate the metal's atomic weight
2.  chemical bond energy in steel
3. how to calculate kj per mole
4. N2- on conceptual level
5. 100 parts a to 3 parts b by weight
6. 35.    how would the following elements become chemically stable?  (which ion would they form?) a.cl b. na c. al
7. how to find empirical formula by making table
8. how to calculate masses of reactants and products
9. which of the following is the best estimate of the percent abundance of the two isotopes of copper?
10. for each of the following balanced reactions calculate how many moles of each product would be produced by complete conversion of 0.50 mol of each reactant

Arsenic Tests

Somewhere around the 8th century, an Arab alchemist produced white arsenic trioxide (As₂O₃) from realgar, a naturally occurring arsenic sulfide mineral, As₄S₄:
As₄S₄ + 7O₂ → 2As₂O₃ + 4SO₂ Arsenic trioxide became one of the most widely administered poisons in history, and therefore, it became necessary to find reliable tests to show whether or not arsenic was present in a sample of food or drink, or whether it was present in a corpse.

In 1775, Carl Wilhelm Scheele treated arsenic trioxide with nitric acid and zinc which resulted in arsine gas (AsH₃), zinc nitrate and water:
As₂O₃ + 6Zn + 12HNO₃ → 2AsH₃ + 6Zn(NO₃)₂ + 3H₂O Arsenic was said to be present if an odour of garlic was produced because arsine gas smells a lot like garlic.

In 1787, Johann Metzger used a carbon reduction method to produce carbon dioxide gas and solid arsenic from arsenic trioxide and carbon:
2 As₂O₃ + 3 C → 3 CO₂ + 4 As As the arsenic trioxide is heated with charcoal, an "arsenic mirror" forms on the charcoal.

In 1785, Samuel Hahnemann produced a bright yellow precipitate of arsenic trisulfide, As₂S₃, by passing a stream of hydrogen sulfide gas, H₂S, through an acidified arsenic solution.

In 1836, James Marsh designed an apparatus that would detect and measure arsenic.
The sample is placed in a flask with arsenic-free zinc and sulfuric acid.
Arsine gas forms:

As₂O₃ + 6 Zn + 6 H₂SO₄ → 2 AsH₃ + 6 ZnSO₄ + 3 H₂O

The arsine gas is fed through a drying tube to a glass tube which is heated.
Arsine deomposes on heating, forming elemental arsenic which is a shiny black substance:

2 AsH₃ → 3 H₂ + 2 As

By placing a cold surface at the end of the heated tube it is possible to condense this arsenic, which forms a black "mirror".

http://www.youtube.com/watch?v=-vUZdAwgl2g

Today, these "wet" methods of chemical detection have been superceded by instrumental analysis. e Atomic absorption spectroscopy (AAS)  can now be used to determine not only the presence of arsenic, but also how much arsenic is present.

Further Reading:
Solubility Rules
Writing Precipitation Equations
Gravimetric Analysis
AAS
Oxidation and Reduction 
Carbon Reduction Methods

Suggested Study Questions:

1. Give the oxidation state (number) for arsenic in each of the following:
   • As₂O₃
   • As₄S₄
   •  AsH₃
   • As
2. For the reaction: As₄S₄ + 7O₂ → 2As₂O₃ + 4SO₂ which element, or elements, have been oxidized?
3.  Consider the reaction: 2 As₂O₃ + 3 C → 3 CO₂ + 4 As
   Is arsenic likely to be more or less active than carbon?
4. Write a possible net ionic equation for the reaction in which arsenic ions react with  hydrogen sulfide gas to produce a precipitate of arsenic trisulfide.
5. Consider the reaction: 2 AsH₃ → 3 H₂ + 2 As which results in the formation of a shiny black "mirror" of arsenic.
   • Has arsenic been oxidized or reduced?
   • Has hydrogen been oxidized or reduced?
   • If 1 mole of arsine gas decomposes completely, how many moles of hydrogen gas would be produced?
   • At 0^oC and 100 kPa, what volume of gas would be produced by the thermal decomposition of 25 moles of arsine?
   •  At 0^oC and 100 kPa, what mass of arsenic would be deposited after  the thermal decomposition of 150 mg of arsine.
   • At 25^oC and 100 kPa, what mass of arsine will decompose to produce 0.05 L of hydrogen gas?
   • A sample of gas containing arsine produces an "arsenic mirror" containing 0.02 g of arsenic. What mass of arsine was present in the gas sample?