Learn About Using the Liter in Chemistry Courses

[brycenrg]

I'm taking my 3rd chem course and I was just wondering why do we use the Liter?
Shouldn't we just use cm^3 on the instruments and use dm^3? I never got it.

 

[fresh_42]

I'm taking my 3rd chem course and I was just wondering why do we use the Liter?
Shouldn't we just use cm^3 on the instruments and use dm^3? I never got it.

Since a liter is $1000 cm^3$ or $1 dm^3$ it doesn't make a difference. Liter is allowed within the SI system so it's just a matter of taste.

 

[Dr. Courtney]

Tradition?

It's not too hard to go back and forth between metric units. 1 L = 1000 cm^3.

 

[Ygggdrasil]

It's also easier to convert between different orders of magnitude (the relationship between L, mL, µL is more apparent than between cm^3, dm^3 etc).

 

[brycenrg]

For a sec I thought order of magnitude was a good enough reason but then I realized when you use maths you don't ever use liter, you convert it to cm^3. So it doesn't make it easier :( lol I guess it's just our primordial slime

 

[Ygggdrasil]

Chemists and biochemists typically do a lot of math involving L. For example, today in lab, I had to figure out how many µL of specific solution (whose concentration was in mg/mL) to get a final concentration of 10 µM in a 20µL reaction. Not impossible to do in terms of cm^3 etc, but using the L system helps a little.

 

[Borek]

I realized when you use maths you don't ever use liter, you convert it to cm^3

In some areas mL (or c³) is preferred over liter, in others it is not.

In general, you choose a unit that is most convenient to use.

I wouldn't say my car burns 7500 mL gasoline per 100 km, I would say it needs 7.5 L per 100 km.

The volume of gas collected at STP when you decompose 1 mole of CaCO₃ is commonly listed as 22.4 L, not 22400 mL.

And the hydrogen tanks of the LZ 129 Hindenburg had a volume of about 200 000 m³, I wouldn't report it neither using L nor mL.

 

[epenguin]

If you look in old textbooks till the 1950's or so I think you will find cc's. I don't know the exact history and the whys of it, but I did see the changeover mnyah mnyah. In the years of school up to English 'O level' (around age 16) I remember nothing but cc's. But then the next two years ('A levels) from the start it had switched over entirely to litres and ml.

I think, at least this is my memory, if you look into scientific book reviews for 10 or 20 years around that time, you'll find them a very often saying 'the MKS system is used' or 'unfortunately the CGS system is used' (or maybe if they were reactionary the other way round). I guess this was important for school purchasing decisions. I seem to remember we had books with both systems; as the conversion is so easy it never bothered me, in fact I never saw what the fuss was about

 

[ogg]

Most of the world uses the liter as THE measuring unit of ( human use size) volume. When is the last time you measured a liquid by measuring its (container's) length, width and height? Who does that? When I was in school, warning! ancient history alert!, the liter was NOT exactly 1000 cm^3, believe it or not. Anyway. You can easily measure volumes (liquids and gasses) in terms of intuitive units of volume, whether gallons or liters, cups or barrels. It requires a bit of abstract thinking to understand that a cubic cm is a unit of volume. Also, (and while this may seem like a restatement of the previous, it really is different) using what to a lot of people is the same unit for length, area, and volume (ie the meter or the centimeter) would cause confusion. It takes some training to understand that multiplying cm x cm does NOT result in cm. If you really think about it, can you explain why cm x cm = cm² ? (Hint: the directions of the basis vectors are orthogonal...but why do you get ANYTHING meaningful when you multiply two orthogonal vectors? And why should we assume that as soon as the "same" units are multiplied, the bases (abstract coordinate system) are orthogonal? See, its a rat hole, better left to those geeks amongst us who can do algebra, etc.

 

[rootone]

A typically full human bladder contains about a liter.

 

[DrClaude]

When I was in school, warning! ancient history alert!, the liter was NOT exactly 1000 cm^3, believe it or not.

I actually did not believe you, because the original definition of the liter after the French revolution was dm³. But you are right! from 1901 to 1964, the liter was defined based on the properties of water, so it was about 1.000028 dm³. Learned something today...

 

[Borek]

I actually did not believe you, because the original definition of the liter after the French revolution was dm³. But you are right! from 1901 to 1964, the liter was defined based on the properties of water, so it was about 1.000028 dm³. Learned something today...

Actually I was taught of liter not being exactly 1000 cm³ somewhere in mid seventies. Probably because it took time for the altered SI definition to seep down.

 

[Rx7man]

I actually did not believe you, because the original definition of the liter after the French revolution was dm³. But you are right! from 1901 to 1964, the liter was defined based on the properties of water, so it was about 1.000028 dm³. Learned something today...

While it's not exact, you're still accurate to 5 significant digits...
The meter is also defined as a portion (is it 1/1,000,000) of the distance from the equator to the north pole?.. A second is also defined as a period of the Earth's rotation (1/(24*60*60)), but the Earth's rotation is measurably slowing down, so either you keep the time period of the old definition and most everyone is happy, or you change it, and every physics constant involving time will have to be recalculated. Just as a year isn't exactly 365 days, a day is not exactly 86400 seconds, and THERE ARE LEAP SECONDS every once in a while.

 

[Borek]

The meter is also defined as a portion (is it 1/1,000,000) of the distance from the equator to the north pole?

Why don't you google that instead of guessing? No, it was never a part of the distance from the equator to the north pole (even if the equator was definitely involved).

 

[Rx7man]

It was in fact.. It was a 10 millionth from the equator to the north pole according to wiki
https://en.wikipedia.org/wiki/Metre

 

[Borek]

Sigh, you learn all your life and you die stupid I swear I was taught it was 1/40000000 of the equator length.

Honestly, I feel like in those films where someone learns he doesn't exist and nobody recognizes him. It was always the equator based definition! Have you edited everything in the world just to make me feel like an idiot?

 

[pbuk]

Most of the world uses the liter as THE measuring unit of ( human use size) volume.

Most of the world calls it a litre.

Sigh, you learn all your life and you die stupid I swear I was taught it was 1/40000000 of the equator length.

Honestly, I feel like in those films where someone learns he doesn't exist and nobody recognizes him. It was always the equator based definition! Have you edited everything in the world just to make me feel like an idiot?

I assume the French, who invented the metre chose their prime meridian as the defining circumference because it passes through Paris whereas the equator does not.

 

[Rx7man]

Sigh, you learn all your life and you die stupid I swear I was taught it was 1/40000000 of the equator length.

Honestly, I feel like in those films where someone learns he doesn't exist and nobody recognizes him. It was always the equator based definition! Have you edited everything in the world just to make me feel like an idiot?

If you're talking about my post, I only edited it for styling and spelling... I didn't edit Wikipedia though.

As for the spelling of meter/metre.. Being in Canada I should abide by the international spelling, but it doesn't make any sense phonetically... If I were speaking french I'd be fine with Metre because then it's phonetically correct.

 

[epenguin]

Sigh, you learn all your life and you die stupid I swear I was taught it was 1/40000000 of the equator length.

Honestly, I feel like in those films where someone learns he doesn't exist and nobody recognizes him. It was always the equator based definition! Have you edited everything in the world just to make me feel like an idiot?

Ah, but if the Earth were spherical it would be exactly the same thing. Perhaps in seventeen ninety-noo they thought it was.

 

[sophiecentaur]

Most of the world calls it a litre.

and they also call a metre a metre. A meter is a measuring instrument and a liter is not part of SI, afaiaa. Liter is, presumably, and Americanism, which is a bit of a librety as they don't even use the damn thing.

 

[fresh_42]

and they also call a metre a metre. A meter is a measuring instrument and a liter is not part of SI, afaiaa. Liter is, presumably, and Americanism, which is a bit of a librety as they don't even use the damn thing.

There are several non SI units which are allowed to use along side the SI system. The liter is one of them.

 

[sophiecentaur]

There are several non SI units which are allowed to use along side the SI system. The liter is one of them.

HAHA. They are only allowed because of usage and inertia and because Europeans are so polite to strangers . It doesn't make them right, though. One of these years, people will start to spell things correctly, put the U in colour, the I in aluminium and the d in pedantry.
But I would have thought that the right spelling would be appropriate in a discussion about SI units. Is there any objection to spelling the units according to the System?

 

[Zachary Smith]

If you're talking about my post, I only edited it for styling and spelling... I didn't edit Wikipedia though.

As for the spelling of meter/metre.. Being in Canada I should abide by the international spelling, but it doesn't make any sense phonetically... If I were speaking french I'd be fine with Metre because then it's phonetically correct.

Focus on the centre of your argument.

 

[fresh_42]

But I would have thought that the right spelling would be appropriate in a discussion about SI units. Is there any objection to spelling the units according to the System?

As English isn't my nature language I follow the spell-check. I don't know whether it's within the platform or the browser. Unfortunately it seems to be an American one. However, it supports my laziness. It simply takes too much time to type words like 'Pittsborough'.

 

[sophiecentaur]

As English isn't my nature language I follow the spell-check. I don't know whether it's within the platform or the browser. Unfortunately it seems to be an American one. However, it supports my laziness. It simply takes too much time to type words like 'Pittsborough'.

If you rely on a spell check to get your Scientific terms right then you risk serious problems at some stage. A spell check is not a sense check and I have a feeling that not many Scientists actually get into writing dictionaries and encyclopediae. Pittsborough may still be a real place on a map and, if the Americans chose to rename their own town Pittsburgh then I will spell it the way they write it on their maps. "Too much time"? There's always time for doing what we want to do (he said, whilst glancing at Facebook and checking his mail).

 

[Zachary Smith]

Proofreading is the cornerstone to successful text messages.
.

 

[sophiecentaur]

Proofreading is the cornerstone to successful text messages.
.

Keep 'em coming!

 

[fresh_42]

If you rely on a spell check to get your Scientific terms right then you risk serious problems at some stage. A spell check is not a sense check and I have a feeling that not many Scientists actually get into writing dictionaries and encyclopediae. Pittsborough may still be a real place on a map and, if the Americans chose to rename their own town Pittsburgh then I will spell it the way they write it on their maps. "Too much time"? There's always time for doing what we want to do (he said, whilst glancing at Facebook and checking his mail).

We call your 'litre' 'Liter' and it happens to be the same way the Americans spell their 'liter'.
Therefore I think I have some right to spell it 'liter' as well.
To call the French 'litre' as witness to consolidate your case I will start to take into account the moment you start to follow Napoleon's regulation and drive on the right side of the road.

 

[sophiecentaur]

We call your 'litre' 'Liter'

But it isn't 'my litre', it's the litre of SI (lower case l), which is the language for communicating in Science.
When in the UK, drive on the left. When in Europe etc. drive on the right. When in Science, use the appropriate language - to avoid misunderstanding. milli and Mega both use an 'emm' but the case has to be right or you fly into the side of a hill.
If someone can't be bothered to follow conventions in units then can they be relied on to follow the conventions of algebra, calculus and geometry? Science and Maths only work when people take stuff seriously. I am only attacking the spelling - not the spellers. Despite everything, you are probably all perfectly nice chaps and do not kick dogs, beat wives or put your elbows on the table.

 

[fresh_42]

But it isn't 'my litre', it's the litre of SI (lower case l), which is the language for communicating in Science.

I am sorry, but the usage of SI does not overrule the rules of language. To derive a frowsy habit on scientific care is ridiculous, if not offensive. Conventions, even those on units, are not context-free. E.g. the meaning of 1 billion differs from country to country. By the way, why did the British changed its usage? Because the colony did?