what are units in chemistry???

[Iwonderaboutthings]

This is a dumb question! however I have been told on this forum that units are just that "units" and they have no meaning.

 

 

But I have read how science in the past have had many accidents because of SI Unit Conversions, or units mistaken in general..

 

I don't see how on earth without math that units could be applied and measured.

Either I am dumb and retarded or someone is pulling my leg.

Edited October 4, 2013 by Iwonderaboutthings

[CaptainPanic]

Units in chemistry?

You mean something like this:

 

kg (amount of matter, in mass)

mol (amount of matter, in moles)

J/kgK (specific heat)

J/kg (enthalpy)

Angstrom (length, bond length)

Celsius or Kelvin (temperature)

 

The list can become quite long...

 

Without math (or numbers), units are quite meaningless. And likewise, without units, you don't know what you're counting.

[ewmon]

Working in terms of "units" lets you work with proportions without using any actual sizes.

 

Let's say you want to make a 20% dilution of a liquid, so you dilute 1 unit of the liquid with 4 units of a solvent. It could be 1 µL with 4µL, 1 cup with 4 cups, 1 gallon with 4 gallons, 1 tanker car with 4 tanker cars, 1 olympic-sized swimming pool with 4 olympic-sized swimming pools, etc.

 

Accidents due to SI unit conversion errors? Oops, the Gimli Glider.

[CaptainPanic]

Working in terms of "units" lets you work with proportions without using any actual sizes.

 

Let's say you want to make a 20% dilution of a liquid, so you dilute 1 unit of the liquid with 4 units of a solvent. It could be 1 µL with 4µL, 1 cup with 4 cups, 1 gallon with 4 gallons, 1 tanker car with 4 tanker cars, 1 olympic-sized swimming pool with 4 olympic-sized swimming pools, etc.

Yeah, or worse... it could be that someone meant 1 kg liquid with 4 kg solvent. If the density of both liquids are not the same, the actual concentration is different than in your example!

 

So, if you express a percentage, make sure to say whether it is a weight-percentage (%wt) or a volume percentage (%vol), or a molar percentage (%mol).

[Bignose]

To add some background, the OP is a misinterpretation of what I posted in this thread: http://www.scienceforums.net/topic/78987-how-do-you-add-exponents/?p=770371

 

To be specific, I was telling him not to place too much emphasis on achieving a specific number, like 1.0 because 1.0 is only meaningful depending on the system of units used.

 

As in, it doesn't mean anything to get 1.0 inches and declare that sacrosanct, because 1.0 inches is also equal to 25.4 mm.

 

If anything, the OP got my point completely backwards, because my point really is that it is of the utmost importance to be sure to write out what units you are using. But the units themselves are just a convention that everyone has agreed to.

 

This is also related to the OP's thread here: http://www.scienceforums.net/topic/79035-numerology-what-is-the-big-deal/ where he is also trying to ascribe significance to specific numbers that arise during a calculation.

[hypervalent_iodine]

!

Moderator Note

I have split off all of the numerology and generally nothing-to-do-with-the-OP posts into the trash. Please try and keep this thread on topic.

 

Also, I wonderaboutthings, let's try and avoid using Uncyclopedia as a reference, shall we?*

 

 

*Question is rhetorical. Don't reply to this in the thread.

[daphne2013]

A lot of units in chemistry may be Particles atoms molecules and nano.

These are all the chemical units.

What type of units do you want to know?

[Iwonderaboutthings]

A lot of units in chemistry may be Particles atoms molecules and nano.

These are all the chemical units.

What type of units do you want to know?

Well, there was an issue earlier on how I may have been confusing numbers and units.

So to say, numbers are used to calculate units, but it seem that units are connected to numbers and so fourth.

Mind boggling. Then chemical equations always must balance? This is also why I confuse numbers and units.

It is this balance I don't comprehend, if numbers are only random things per say then how can you balance randomness?

 

However, since chemical units are confirmed, could there also be something as an exponent "chemical unit?"

 

 

In other words, lets take G 9.8 m/s, could G be an exponent of x^2 as in this " example" x^9.8.

I am assuming this " somehow" could be the case.

 

But then how would you use x then?????

 

What confuses me is this:

 

The exponent then is a ratio ??????????

 

 

Is this why balance is so required in chemistry?

Since chemistry adheres to atoms and electron orbitals I could only assume balance applies to all fields of science, not just chemistry..

 

But again:

 

Units, Numbers and Fundamental Constants are all connected to units and random numbers.

Although in my opinion it seems this balance is all connected to time no matter how you look at it.

Edited October 27, 2013 by Iwonderaboutthings

[Sensei]

Units, Numbers and Fundamental Constants are all connected to units and random numbers.

What random numbers you are talking about?!

 

If you'll measure your mass to be f.e. 78 kg it means that you are made of:

 

mass of proton/neutron is approximately 1 g/Na= 1 g/6.022141*10^23 = 1.66 * 10^-24 g ... 1.67 * 10^-24 g (different element have different mass of protons and neutrons f.e. Carbon-12 has mass=12 g/Na, but Hydrogen has mass 1.0078 g/Na)

 

78 kg = 78000 g

 

78000 g / 1.67 * 10^-24 g = ~4.67 * 10^28 protons and neutrons approximately in 78 kg body..

 

 

How can we calculate mass of Hydrogen and Oxygen? While electrolysis..

 

We are filling box with well known mass and volume of water.

Then start electrolysis.

In one test tube there is collected Hydrogen and in other test tube is collected Oxygen.

We can measure volume of Hydrogen, volume of Oxygen, mass and volume of rest of water in box..

Using Hydrogen and Oxygen as product to create other substances we can gain knowledge about molar masses of the all elements..

And you can do it in couple minutes at home.

Edited October 27, 2013 by Sensei

[Iwonderaboutthings]

What random numbers you are talking about?!

 

If you'll measure your mass to be f.e. 78 kg it means that you are made of:

 

mass of proton/neutron is approximately 1 g/Na= 1 g/6.022141*10^23 = 1.66 * 10^-24 g ... 1.67 * 10^-24 g (different element have different mass of protons and neutrons f.e. Carbon-12 has mass=12 g/Na, but Hydrogen has mass 1.0078 g/Na)

 

78 kg = 78000 g

 

78000 g / 1.67 * 10^-24 g = ~4.67 * 10^28 protons and neutrons approximately in 78 kg body..

 

 

How can we calculate mass of Hydrogen and Oxygen? While electrolysis..

 

We are filling box with well known mass and volume of water.

Then start electrolysis.

In one test tube there is collected Hydrogen and in other test tube is collected Oxygen.

We can measure volume of Hydrogen, volume of Oxygen, mass and volume of rest of water in box..

Using Hydrogen and Oxygen as product to create other substances we can gain knowledge about molar masses of the all elements..

And you can do it in couple minutes at home.

thanks will do..

[Sensei]

To create just Hydrogen and Oxygen you need to use right material for electrodes.

http://en.wikipedia.org/wiki/Electrolysis_of_water

On picture on the right there are used pencils. That's no joke. Graphite is very good for this kind of job. But it's hard to find really pure one in the shops (at least here).. I went to the shop with multimeter and checked the all they gave me to make sure they're passing current (~75% did not work).

 

If you will use metal such as f.e. Aluminum on one electrode there will be created Hydrogen with normal volume, but on second one much less than expected volume of Oxygen (1/8 volume of that of Hydrogen) - the rest of Oxygen will join with Aluminum and produce Al2O3 (I have couple liters of it at home exactly from electrolysis..) part/all of Aluminum electrode will literally disappear. One hour of electrolysis with 230 VDC (using silicon bridge rectifier KBPC-610 6A/1000V that cost 0.5$) is enough for wiping out entire electrode made of 0.5mm Aluminum plate. With such setup you can create 25 ml (single test tube) of Hydrogen in 91 seconds, and nearly 1 Liter in 1 hour.

 

Different metals will produce different substances.

 

You will see it immediately as f.e. some colorful substances in water making it opaque for a while.

 

After leaving them alone f.e. for night or longer they will sink to bottom of container.

 

For instance steel electrodes are producing red-yellow water, and absolute no Oxygen in test tube, so entire Oxygen is reacting with Iron..

 

And again - this can be used to measure masses of either Oxygen and metals. Measure mass of metal electrode prior electrolysis and after electrolysis (when part of it literally disappeared - it's now dissolved in water).

After getting rid of water from container, there will remain just metal oxide, and you can measure its mass..

Edited October 30, 2013 by Sensei