Say hello to the Facebook Chemistry Chatbot!

Please say a big hello to the Facebook Chemistry Chatbot!

I am ridiculously excited by this as I think chatbots are potentially an excellent way to learn new things and to share information. It feels so much better to be ‘chatting’ on Facebook Messenger about chemistry and biology maths, than working through a website. It just feels better… It feels more natural.

You can find the Chatbot at:

Or you can just scan this code:

Facebook Chemistry Chatbot

Facebook Chemistry Chatbot – just scan this code with Facebook Messenger

To scan the code in Facebook Messenger:

  1. From Facebook Messenger Home, tap your profile picture in the top left corner.
  2. On your profile page, tap your picture at the top of the page.
  3. Tap Scan Code tab at the top of the page and get the above code in the circle.

So, what can the bot do? Well, you can ask it questions such as:

  • What is a mole?
  • What is molarity?
  • How do I calculate molarity?
  • How do I work out a dilution?
  • What is sodium?
  • What is Mg?
  • What is NaCl?
  • Plus many more…

And you will get a reply with some useful links.

Now, I am not claiming the bot knows everything there is to know about chemistry, but it does know a lot of the key terms, all the elements, and a lot of the common molecules and compounds you would find in a typical school, high school, college or university lab.

If you ask it something about chemistry and it doesn’t know the answer then drop me a line at nick@ and I will ‘teach’ the bot the new thing.

And the bot can ask you calculation questions for moles, molarity, dilutions, percentage solutions, and units. Try asking:

  • Test me on moles
  • Quiz me on molarity
  • A percentage test, please
  • Dilutions test
  • Please test me on units

You will then get a question to which you provide an answer, and if you get it right the bot will tell you, and if you get it wrong, the bot will give you the correct answer and explain how to work it out.

If there is another type of question you would like included then please email the details: nick@ and I will have a look at getting it added.

If you have any comments or questions about the Facebook Chemistry Chatbot then either leave a comment below or email me at nick@



Why is memorising the molarity formula a bad idea?

OK,  so maybe you’re here for the molarity formula, in which case here it is:

Molarity = the number of moles / volume in liters

The molarity of a solution is the number of moles present, divided by the volume of the solution in liters.

That is it, that is all there is you need to know or is it? Is there more to this than meets the eye? If you really want to understand molarity then you need to understand moles and why they are important, and how they relate to molarity, so below I will cover:

  1. What is a Mole?
  2. Why are Moles important?
  3. How do I know how many atoms, ions or molecules I have?
  4. What is Molarity?
  5. Summary

And I would argue that just remembering the formula is a bad idea because under the pressure of exams, or in the lab, you may forget it, or get confused. However, if you understand moles and molarity, and how they are related, then you are less likely to forget.

What is a mole?

A mole is a certain number of atoms, ions or molecules.  In the previous sentence, the keyword is number – a mole is not a weight or an amount of something, it is a number, it is a count.

moles and molarity

This is NOT the type of moles I am talking about…

One mole of something is actually equal to 6.0221415 × 1023 of that something, and that, I think we can agree, is a very big number, but interestingly we don’t need to worry about it. All we need to know is that a mole is a count of something. So, 1 mole of atoms would contain 6.0221415 × 1023  atoms, 1 mole of ions would contain 6.0221415 × 1023  ions, and, you guessed it, 1 mole of molecules would contain 6.0221415 × 1023  molecules. (By the way, 6.0221415 × 1023 is the Avogadro constant and is derived from the number of atoms on 12 g of carbon-12.)

Why are moles important?

Moles are important because atoms, ions, and molecules will react together in 1:1, or 1:2, 1:3, etc. configurations. That is, 1 atom of sodium will react with 1 atom of chlorine to make 1 molecule of sodium chloride.

moles and molarity reaction

A one-to-one (1:1) reaction – one molecule (or atom) of A reacts with one molecule (or atom) of B.

So, if we want to make 10 molecules of sodium chloride, we would take 10 atoms of sodium and add 10 atoms of chlorine. We would count out the 10 atoms of sodium, and 10 atoms of chlorine, and combine them. And here is the key point, we wouldn’t weigh out 10 g of sodium and 10 g of chlorine because sodium atoms and chlorine atoms weigh different amounts, and so 10 g of sodium would contain more atoms than 10 g of chlorine as a sodium atom weighs less than a chlorine.

molarity and moles reaction

A one-to-one (1:1) reaction – many molecule (or atom) of A reacts with many molecule (or atom) of B. The ratio of A and B reacting is still 1:1.

If we mixed 10 g of sodium with 10 g of chlorine, we wouldn’t get 10 g of sodium chloride, and I’ll explain why, and what we would get, below.

How do I know how many atoms, ions or molecules I have?

This is where atomic weights, in the case of atoms, or molecular weight, in the case of molecules, comes in. (Ions can have an atomic weight if the ion is a charged atom, or a molecular weight if the ion is a charged molecule.)

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The atomic or molecular weight of something is how much 6.0221415 × 1023 atoms would weigh, and the molecular weight of a molecule is how many 6.0221415 × 1023 molecules would weigh.  It is the weight of one mole. It is the weight of 6.0221415 × 1023 atoms, ions or molecules. That is it…

If you counted out 6.0221415 × 1023 atoms of something you would have 1 mole, and the weight of that pile of atoms would be the atomic weight.

So, if something has a molecular weight of 10 g/mol (grams per mole) and you weigh out 10 g, you will have 1 mole which is 6.0221415 × 1023 molecules.  If you weigh out 5 g, as 5 is half of 10, you have 0.5 moles. 20 g would give you 2 moles. And this brings me to the first thing you need to remember:

The molecular weight of something is the number of grams that make one mole

Let’s go back to sodium and chlorine. The atomic weight of sodium is 22.9898 g/mol, and for chlorine, it is 35.453 g/mol. Therefore if I weigh out 22.9898 g of sodium I would have 6.0221415 × 1023 atoms of sodium, and 35.453 g of chlorine would give me 6.0221415 × 1023 atoms of chlorine.

Therefore to react sodium and chlorine 1:1 I would have to weigh out 22.9898 g of sodium, and 35.453 g of chlorine (these two weights would contain the same number of atoms). If I didn’t want to make that much, i.e. 1 mole of sodium chloride, I could go for an equal fraction of each. So, say I wanted to make 0.1 moles of sodium chloride then I would take 22.9898 x 0.1 = 2.29898 g of sodium, and 35.453 x 0.1 = 3.5453 g of chlorine.

In the case above where we had 10 g of sodium and 10 g of chlorine things are a bit different. Yes, the weights are 1:1, but what we need is the atoms to be 1:1, and we know a chlorine atom weighs more than a sodium atom.

Well in the case of sodium we would have 10 / 22.9898 = 0.435 moles, and for chlorine, 10 / 35.453 = 0.282 moles. As sodium reacts with chlorine 1:1 then we could react all 0.282 moles of chlorine with the 0.435 moles of sodium, which would leave 0.435 – 0.282 = 0.153 moles of sodium unreacted (or 0.153 x 22.9898 =  3.517 g of sodium). The reaction would yield 0.282 moles of sodium chloride, which has a molecular weight of 22.9898 + 35.453 = 58.4428 g/mol, so we would have 0.282 x 58.4428 = 16.480 g of sodium chloride, plus 3.517 g of sodium left over. We certainly wouldn’t have 20 g of sodium chloride.

Reaction - Moles and Molarity

Moles are important because by working in moles we keep the number of atoms or molecules present equal. For example, say B weighs 2 g each, and A weighs 1 g. If I weigh out 4 g of A, I will have 4 As, but if I weigh out 4 g of B I will only have 2. If I react A with B, and they combine 1:1, then the 2 B will combine with 2 A, and this will leave 2 A leftover.

What is molarity?

Molarity is just a concentration. It is the number of moles per volume of liquid. It is moles per liter. So, 1 mole of something made up to 1 liter, would be a 1 Molar solution (we write that as 1 M). And this brings me to the second thing to remember:

1 mole made up to one liter gives a 1 Molar solution

Now above we said that the molecular weight of something is the number of grams that make one mole, so we can replace “1 mole” in the above with molecular weight, and this gives us the third thing you need to remember:

The molecular weight of something made up to one liter gives a 1 Molar solution

So using our example above of a substance with a molecular weight of 10 g/mol if we took 10 g, dissolved it in water, and made the volume up to 1 liter, then we would have a 1 M solution.

Some more worked examples of this:

  • If we took 5 g of the same substance and made it up to 1 liter with water, we would have a 0.5 M solution.
  • If we took 20 g of the same substance and made it up to 1 liter with water, we would have a 2.0 M solution.
  • If we took 5 g of the same substance and made it up to 0.5 liter with water, we would have a 1.0 M solution.

In the above examples, all have to do is take the amount of substance, say 5 g, and divide that by the molecular weight – 10 g/mol, to give the number of moles, which is 0.5 moles. Next, look at the volume, if it is 1 liter, then you have 0.5 moles per 1 liter, or 0.5 mol/l. And as mol/l is Molar, then we have 0.5 M.

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So for 5 g of substance in 0.5 liters. We have 5 g of a substance with a molecular weight of 10 g/mol, hence we have 0.5 moles (5/10 = 0.5). This 0.5 moles is in 0.5 liters, so to get to 1 liter we need to double the volume (2 x 0.5), and as we have multiplied the volume by 2, we have to do the same to the moles, so we get 0.5 x 2 = 1. Hence, the answer is 1 M. We are just dividing the number of moles by the volume in liters, for example, 0.5 moles in 0.25 l is 0.5 / 0.25 = 2 M. And again, 0.1 moles in 0.4 liters is 0.1 / 0.4 = 0.25 M.

There is a formula you can use to work this out, and it can be derived from what we have discussed above, and the formula is:

M = g / (MW x v)

Where: M = molarity (M); g = mass in grams; MW = molecular weight (grams per mole); v = volume (liter)

In the lab you may be asked to make up a certain volume of a solution at a given molarity. For this you need to rearrange the above equation so that you can solve for grams (g):

g = M x MW x v

However, it is tricky to remember these two equations and under pressure, in an exam or in the lab, you may get things confused.

Is it M = MW / (g x v) or M = g / (MW x v)?

But I think you are less likely to forget:

The molecular weight of something made up to one liter gives 1 Molar solution

and by remembering the above you have molarity covered, and you can quickly and easily derive the equations to answer the questions.

Phew…  That turned out to be a much longer post than I thought it would be. However, an understanding of moles and molarity is critical, so it is worth the effort of getting a good understanding of this material. As I said above, I think the key is:

The molecular weight of something made up to one liter gives 1 Molar solution.


So, you could just remember the molarity formula:

Molarity = the number of moles / volume in liters

But, by know of what moles are, why they are important, and how they relate to molarity, you get a much better understanding as to what the formula means, and you are less likely to forget it under the pressure of exams or in the lab.

If you would like a copy of this post for your notes then grab the free Maths4Biosciences eBook. Besides the material above it also has sections on percentage solutions, dilutions, and how to draw a graph in the lab.

Copy of this blog post: Get the free Maths4Bioscienes eBook – Maths4Biosciences eBook

Standard curve: A new test on maths4bioscience

A new test has been added to the maths4bioscience website – The Standard Curve.

So what is a “standard curve”?

A “standard curve” is a graph that is generated using known concentrations or amounts of something to produce a reading. The reading could be an absorbance, conductivity, fluorescence, pretty much anything that can be measured. The collected readings are then used to plot a graph of known amount or concentration against the thing that is being measured. This graph is a standard curve, which you can then use to determine the concentration or amount present in an unknown sample.

A very common type of “standard curve” is the protein determination standard curve. In this case, a range of known concentrations of a protein are used, and their absorbances are measured using a spectrophotometer. Plot the absorbances against the protein concentrations, and you have a standard curve. You cane now use the graph to determine the concentration of protein in a solution with a known absorbance.

Using data derived in the lab to plot a standard curve is a key skill for a bioscientist. And the new test allows you to practice your graph plotting and calculation of the unknown concentration of some protein samples.

So what is the “standard curve” test?

The test presents you with a table of data of absorbances for a range of known protein concentrations. You are also given the absorbances of three protein samples of unknown concentrations.


Using the data, you plot a standard curve. (If you have trouble drawing graphs then have a look at the blog post on How to draw a graph – there is also a graph drawing video on YouTube.)

Graph Drawing Checklist: Get a checklist for graph drawing – Send the Checklist


And using the standard curve you then determine the protein concentrations of the three unknowns.


Once you have determined the protein concentrations, and also calculated the extinction coefficient, you enter the data and click mark.

The site will then give you feedback on your answers, including showing you the standard curve for the data. If you get things right then all you see is the graph and the answers.


If you get any of the answers wrong then you still get the graph, plus an explanation of how to work out the correct answers.


Graph Drawing Checklist: Get a checklist for graph drawing – Send the Checklist


The data for the standard curve, along with the absorbances for the three unknowns, is randomly generated and so this means that the site can you provide you with countless questions for you to answer.

If you are struggling with your graph drawing, and getting good data plots, then you might like to take the free Maths and Chemistry Refresher Course we offer at Maths4Biosciences.

If you found this blog post interesting or useful then please share it with your friends and classmates via email, Twitter or Facebook.

Bioscience maths skills – are they really needed?

What are bioscience maths skills and why do bioscientists – chemists and biologists, and even a pre-med students and medical doctors, need a good understanding of what I call “science maths”? Are bioscience maths skills really that important?

Below you will find a video (and also a slide stack) on why I think it is important that bioscientists have a good grasp of the what I call “science maths” – that is, why I think it is important that bioscientists understand the concepts of moles and molarity, and an understanding of the role of atoms, molecules, and ions in health and disease. These skills, along with correct pipetting, and working accurately and consistently in the lab, are critical if you are going to get good results, and if you are a student, in getting good grades.

It is important that you develop your understanding of moles and molarity, percentage solutions, and dilutions now so that the “science maths” becomes second nature and you don’t find yourself second guessing in the lab. And the best way to improve your bioscience maths skills is through practice and working through the material.

If you have found the slide stack and video useful then please share them with your friends and classmates. You may also like to check out the course we have on offer to help you with your bioscience maths skills over at Fedora – we have a range of courses from basic chemistry and maths skills, through to moles and molarity, and on to spectrophotometry.

How to draw a graph

How to draw a graph

Hand drawing a graph is an essential skill for any science (physics, chemistry, or biology) or maths students. You need to know how to draw a graph by hand before you move on to use a computer program to produce your graphs.

In the above video I will show you the key components required to produce a good graph. These include:

  • making the best use of the graph paper
  • adding the correct labels

In addition, I will also show you how to construct a standard curve using data from a protein assay, and how to use the graph to determine the unknown concentration of a sample.

If you are struggling to draw good graphs then this handy checklist will help you produce good quality graphs:

Graph Drawing Checklist: Get a checklist for graph drawing – Send the Checklist

If you are struggling with your graph drawing, and getting good data plots, then you might like to take the free Maths and Chemistry Refresher Course we offer at Maths4Biosciences.

There is also a slide stack available over at


If you are looking for a way to brush up your ‘science maths’ skills then please visit where you will find a wide range of online tools to test your understanding of the maths you need for your biology and chemistry courses.


What is ‘science maths’?

I talk about ‘science maths’ all the time, but what do I mean by it? Sometimes I call it ‘maths for the biosciences’ or ‘maths for bioscientists’. (Or I could say ‘science math’, ‘math for the biosciences’ or ‘math for bioscientists’).

What is 'science maths'?

What is ‘science maths’?

Well, in biology and chemistry you need some maths to work out concentrations, dilutions, and a bunch of other stuff. And it can be a struggle, and over the years I have found when working with students that the secret to understanding the maths is not remembering the formula, but to understand the underlying principles so that any ‘formula’ needed can be derived, and to practice, practice, practice doing the maths.

The website – Maths4Biosciences – provides a site that can be used to practice the maths again, and again, and again, as the site contains potentially thousands of possible calculations for you to try (all with a ton of feedback). If you go to the Maths4Biosciences Courses site you will find some courses to help you gain further understanding:

Why is maths important in biology and chemistry

An understanding of maths, moles, molarity, dilutions etc. is very important in biology and chemistry, and I think my best attempt at summing up this importance can be seen in the slide stack below:


So, what is this all about?


Get your science maths right….

Well, it is a new site, and a new blog dedicated to explaining the maths skills biology and chemistry students will need to develop to pass their courses.

The Site

The website is designed for students to test their understanding of some of the types of calculations they will have to do when studying chemistry and biology at high school, college, and university. Specifically, the types of calculating covered are:

  • Converting between units, e.g. mM to µM, etc.
  • Working with percentage solutions
  • Calculating moles and molarities
  • Calculating volumes and concentrations in dilutions
  • How to calculate concentrations from spectrophotometry data
  • Working with extinction coefficients
  • Enzymatic kinetics (calculation of Vmax and Km (Michaelis–Menten kinetics)
  • Determination of the concentration of an unknown from spectrophotometry data (coming soon)
  • ELISA data calculations (coming soon)

Each type of calculation test provides 1000s of possible questions, so you should never encounter the same set of numbers twice. The site is also ‘responsive’ which means it works on desktops, tablets, and smartphones.

One great thing about the tests is if do you get the answer wrong you will be provided with a detailed breakdown (feedback), using the actual numbers in the question, that explains how you can get the right answer.

The Blog

The blog (which you are currently reading) will provide some additional examples of how to tackle the types of questions, on the site and some posts that expand on my answers on Quora.

The blog will also host notifications of when I post new videos on YouTube and stacks on Slideshare.

There will also be notifications of when new biology and chemistry maths courses become available at Maths4Biosciences Courses. The current courses cover:

And there are more courses to follow.

There is also an iPhone App – chemCal available, which you can use to perform dilution, molarity, and dilutions calculations.

To keep up with all of this you may want to subscribe to the newsletter or follow on Twitter.

Why is ‘science maths’ important?

Well, a good understanding of the maths behind chemistry and biology is very important for your studies and your research. I think I best describe the importance in the slide stack below:


About the author of this blog and website

The author of this blog and the website has over 15 years of experience teaching ‘chemistry maths’ to bioscience students at university. I have over 25 years of lab experience, I have published a number of scientific papers in peer-reviewed journals, and I have been ‘playing around with computers’ since the late 1970s. I coded his first website in 1994, and I have written, and sold applications, for the Mac, iPhone, and iPad. I am a geek and proud of it.