GCSE question

[Delbert]

Today my newspaper (UK) reproduced some sample GCSE questions. And they left me baffled - I certainly would have failed such a test.

One chemistry question asked: Complete the word equation for the oxidation of hydrogen. hydrogen + oxygen =?

 

The answer is water. So where did the second hydrogen atom come from?? It doesn't say hydrogen2, it just says hydrogen! And what's more if two hydrogen are somehow to be assumed, why not assume two oxygen - or any other numerical combination? Surely, if it means two it should say or indicate two.

 

There is another whereby numbers seem a tad loose. Anyway, the upshot is I'd fail a GCSE test with flying colours.

 

[ajb]

The question seems a little loosely worded as you say, but the answer is clear. No need to over think GCSE questions.

[hypervalent_iodine]

Today my newspaper (UK) reproduced some sample GCSE questions. And they left me baffled - I certainly would have failed such a test.

 

One chemistry question asked: Complete the word equation for the oxidation of hydrogen. hydrogen + oxygen =?

 

The answer is water. So where did the second hydrogen atom come from?? It doesn't say hydrogen2, it just says hydrogen! And what's more if two hydrogen are somehow to be assumed, why not assume two oxygen - or any other numerical combination? Surely, if it means two it should say or indicate two.

 

There is another whereby numbers seem a tad loose. Anyway, the upshot is I'd fail a GCSE test with flying colours.

 

It is assumed knowledge that both hydrogen and oxygen are diatomic. This is also not an obscure reaction for anyone studying chemistry; it is a simple combustion reaction.

 

Edit: this is not to disparage you in any way. If you haven't studied chemistry very much, then of course the answer might not have come by easily.

[Delbert]

The question seems a little loosely worded as you say, but the answer is clear. No need to over think GCSE questions.

Well, not quite sure what to say about such, apart from if I were taking the exam hoping the examiner doesn't over think the answers! But I bet that wouldn't be the case - they would be picked over in detail..

[DrP]

It says to complete the 'WORD' equation... it doesn't ask for a balanced numerical equation.

[Delbert]

It is assumed knowledge that both hydrogen and oxygen are diatomic. This is also not an obscure reaction for anyone studying chemistry; it is a simple combustion reaction.

Yes perhaps we all know O2 and H2. So, assuming they are also saying the oxygen is really oxygen2, why is the answer (water) saying nothing about the spare oxygen that presumably floats off to who knows where?

 

As said, there is another question where numbers seem very flexible, but I'll leave it as just this one as I'm still puzzled by the lack of precision. Is one to presume therefore, that when reading a chemical formula there will be one or two, if not lots, of missing numbers whereby one is to 'just assume'?

 

Also as I indicated in my reply above, would the examiner when reading (say) my answer adopt a similar laxity? I'd bet a bob or two that he or she wouldn't.

[hypervalent_iodine]

Yes perhaps we all know O2 and H2. So, assuming they are also saying the oxygen is really oxygen2, why is the answer (water) saying nothing about the spare oxygen that presumably floats off to who knows where?

 

As said, there is another question where numbers seem very flexible, but I'll leave it as just this one as I'm still puzzled by the lack of precision. Is one to presume therefore, that when reading a chemical formula there will be one or two, if not lots, of missing numbers whereby one is to 'just assume'?

 

Also as I indicated in my reply above, would the examiner when reading (say) my answer adopt a similar laxity? I'd bet a bob or two that he or she wouldn't.

It's a worded question, it doesn't need to be balanced with coefficients. Converting the worded equation to the chemical equation would necessitate that it then be balanced (in this case to 2H2 + O2 --> 2H2O). Stating 'hydrogen' and 'oxygen' is the same as writing H2 and O2 - these are their elemental forms and hence the name hydrogen, etc. refers to the diatom by convention. This is common knowledge.

 

In any event, I'm not really sure I see the issue. The question has perfectly enough information and precision to be answered correctly and without trouble for someone studying chemistry, IMO.

 

What would you call laxity in an answer to this question? I'm not sure how you could logically answer anything besides water.

[StringJunky]

Half the solution to a problem is fully understanding the question.

[Strange]

It says to complete the 'WORD' equation... it doesn't ask for a balanced numerical equation.

 

Exactly. One of the things you are told over and over is to answer the question that was asked - not the question you think should have been asked!

 

I assume, also, that the students would have been introduced to this sort of informal "word equation" (this is not a term I have come across before but seemed pretty transparent in the context).

[Fuzzwood]

And besides, the answer is incomplete. It should be water + energy.

[hypervalent_iodine]

And besides, the answer is incomplete. It should be water + energy.

Well, not really. That would only need to be included in the reaction if they were specifically asked to include it. Otherwise, leaving out the energy component is fine and I certainly wouldn't call a reaction that omits it as incomplete.

[studiot]

Strange has it with that old saw

 

Read the question, then check you have read it correctly.

 

 

Yes perhaps we all know O2 and H2. So, assuming they are also saying the oxygen is really oxygen2, why is the answer (water) saying nothing about the spare oxygen that presumably floats off to who knows where?

 

Whilst it is indeed common practice to omit chemicals that take no part in a reaction, the question specifically asked about those that did.

 

So any 'spare' oxygen that took no part and remained unchanged would not be recorded.

 

It would also be the case for any 'spare' hydrogen if there was excess of that substance, which is possible.

 

You cannot include energy without stating more detail about the initial and final conditions.

Edited June 2, 2015 by studiot

[Delbert]

 

Exactly. One of the things you are told over and over is to answer the question that was asked - not the question you think should have been asked!

Exactly! I'm reading it as written and it says hydrogen and oxygen - one of each. It was a question from a chemistry paper and not a general knowledge question.

 

Anyway, it's clear my approach, or even understanding, is wrong, and as I've said, I would have failed the test with flying colours.

 

Perhaps it may come as no surprise to anybody that I am, and always have been, a total failure in exams and tests.

[studiot]

 

Exactly! I'm reading it as written and it says hydrogen and oxygen - one of each

 

 

No it is a word equation.

 

If definite or even equal quantities were intended then the equation would have included words to suit.

 

The only safe conclusion you can draw is that

 

some hydrogen + some oxygen

 

or

 

an indefinite amount of hydrogen reacts with an indefinite amount of oxygen.

 

That is correct use of words.

[Strange]

Exactly! I'm reading it as written and it says hydrogen and oxygen - one of each.

 

But it doesn't say one of each. Hydrogen and oxygen (and water, and beer, bread, etc) are non-count nouns. It is ungrammatical to say "one hydrogen".

 

If they had meant one hydrogen atom then they would have written "one hydrogen atom".

Edited June 2, 2015 by Strange

[DrP]

QUOTE:"As written it says hydrogen and oxygen - one of each'

 

No it doesn't.... it doesn't say 'one of each' at all. It says 'hydrogen and oxygen' which means 'some hydrogen gas and some oxygen gas' (As Studiot has just written above before I got in there)... and the result of that reaction is 'some water'....

 

They might go on to ask as a continuation of the question for you to balance the chemical equation... then you will give the full equation as in post 7.

[Delbert]

 

If they had meant one hydrogen atom then they would have written "one hydrogen atom".

Okay, 'hydrogen' actually means either two hydrogen atoms or one hydrogen molecule. So, presumably why then does 'oxygen' clearly only mean one oxygen atom? Surely using the same logic that means two oxygen atoms or an oxygen molecule?

 

I'm sorry but all this seems ridiculous. In chemistry I understand two hydrogen atoms would be 2hydrogen, and a hydrogen molecule would be hydrogen2.

 

Again, I would fail the test magnificently.

[studiot]

Here is an extract from the GCSE syllabus.

 

Note that word equations do not require quantities or balancing and that excess reactants are not mentioned.

In fact balancing is only reuqired in the 'higher tier'

 

 

C1.1.3 Chemical reactions

a) When elements react, their atoms join with other atoms to form compounds. This involves giving, taking or sharing electrons to form ions or molecules. Compounds formed from metals and non-metals consist of ions. Compounds formed from non-metals consist of molecules. In molecules the atoms are held together by covalent bonds.

Additional guidance:

Further details of the types of bonding are not required.

Candidates should know that metals lose electrons to form positive ions, whereas non-metals gain electrons to form negative ions. Knowledge of such transfers is limited to single electrons.

b) Chemical reactions can be represented by word equations or by symbol equations.

Additional guidance:

Candidates should be able to write word equations for reactions in the specification. The ability to interpret given symbol equations in terms of numbers of atoms is required.

Higher Tier candidates should be able to balance symbol equations.

 

 

Here is an extract from a chemistry helpsite with a similar question about the reaction between iron and oxygen.

 

Note that there are different oxides of iron but you don't even need to know which one.

 

 

Word equations

Theory

A word equation describes a chemical reaction using words.

 

1. In the naming of compounds between metals and non-metals

• metallic elements are named first
• non-metallic elments are named second and the suffix is changed to to an "ide"

Non metal Suffix change Non metal Suffix change Hydrogen Hydride Fluorine Fluoride Oxygen Oxide Chlorine Chloride Sulfur or sulphur Sulfide or sulphide Bromine Bromide Nitrogen Nitride Iodine Iodide Phosphorus Phosphide Astatine Astatide

Examples: Sodium chloride, magnesium oxide, sodium fluoride and potassium iodide.

 

2. In all chemical reactions mass is conserved. Atoms of elements are rearranged.

• Iron + oxygen → iron chloride Oxygen atoms do not change into chlorine atoms!
• Iron + oxygen → iron oxide The same type of atoms are on opposite sides on the equation

[hypervalent_iodine]

Delbert, it is a worded question and says nothing about the stoicheometric coefficients of the things involved. All it tells you is that there is some H2 and some O2 reacting and this is all you need to answer the question. The relative amounts do not enter into it here at all - stop confusing yourself by thinking otherwise.

 

Where I am from, these sorts of reactions and the interpretation of worded equations is something taught in grade 10 or 11 (it is assumed knowledge thereafter). It is neither obscure nor difficult to decipher for anyone with this level of knowledge fresh in their minds.

Edit: it is also not an unusual thing to have to predict the product of an unbalanced reaction. Balancing tends to come after.

[Strange]

Okay, 'hydrogen' actually means either two hydrogen atoms or one hydrogen molecule.

 

No it doesn't. Hydrogen means the element, in general, or the gas. It says NOTHING about the number of atoms.

 

You would deserve to fail this, or any other reading comprehension test, at this rate.

[Delbert]

 

No it doesn't. Hydrogen means the element, in general, or the gas. It says NOTHING about the number of atoms.

I know, I know. I was just going along with your apparent interpretation that to specify only one hydrogen atom it likely say only 'one hydrogen atom'.

 

It appears I can't win. If I suggest one view (mine) it is countered. And then if I acquiesce to what appears to be the contrary view, I'm told I'm still wrong!

 

When I said "Okay, 'hydrogen' actually means either two hydrogen atoms or one hydrogen molecule." I was tempted to say 'any number from two to eternity'. But I didn't want to introduce another factor to confuse things and be shot down again on such complication!

 

This was a chemistry paper not a general knowledge paper. Yes, it uses 'word' in the question, but that meant nothing particular to me because what else would one use to identify what the formula referred to? Perhaps I should prefix this reply by saying 'this is a word reply' - clearly ludicrous, which was my puzzlement with 'word' in the question.

Edited June 3, 2015 by Delbert

[StringJunky]

..

Perhaps I should prefix this reply by saying 'this is a word reply' - clearly ludicrous, which was my puzzlement with 'word' in the question.

The question author was being explicit that ratios or numbers were not relevant in order to, hopefully, avoid any confusion but, alas, it didn't work with you.

Edited June 3, 2015 by StringJunky

[studiot]

 

This was a chemistry paper not a general knowledge paper. Yes, it uses 'word' in the question, but that meant nothing particular to me because what else would one use to identify what the formula referred to? Perhaps I should prefix this reply by saying 'this is a word reply' - clearly ludicrous, which was my puzzlement with 'word' in the question.

 

 

 

You are quite entitled to be puzzled about the use of the term 'word question'

This is a new idea as presented nowadays and seems to be causing much trouble in teaching and learning circles if the new crop of question from posters who say they have trouble with 'word questions' is anything to go by.

 

However it was specifically not just a chemistry paper, but a GCSE chemistry paper, and I posted the specification for 'word question' on GCSE chemistry papers showing they specifically exclude numbers.

 

So chalk it up to experience.

I too am finding new challenges since 'word questions' appeared in the current guise.

I was even thinking of starting a disussion thread about the subject since so many are experiencing difficulty it is making matters worse, not better.

 

 

Edited June 3, 2015 by studiot

[StringJunky]

 

 

You are quite entitled to be puzzled about the use of the term 'word question'

This is a new idea as presented nowadays and seems to be causing much trouble in teaching and learning circles if the new crop of question from posters who say they have trouble with 'word questions' is anything to go by.

 

However it was specifically not just a chemistry paper, but a GCSE chemistry paper, and I posted the specification for 'word question' on GCSE chemistry papers showing they specifically exclude numbers.

 

So chalk it up to experience.

I too am finding new challenges since 'word questions' appeared in the current guise.

I was even thinking of starting a disussion thread about the subject since so many are experiencing difficulty it is making matters worse, not better.

 

 

I've seen homework questions for teenagers and younger and they may as well be in a foreign language for all I understand. Is this what it's like to get older?

Edited June 3, 2015 by StringJunky

[DrP]

@Studiot: Relatively new idea? I done my GCSE's back in the 1980's - we were the first to do them. The idea of writing out a 'word' equation rather than a balanced chemical equation is something I remember as being pretty standard. How is it new?

Edited June 3, 2015 by DrP