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Facts about Methanol: Density & Molar Mass

Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

Although methanol may be a type of alcohol, this is not the type of alcohol that should first come to mind regarding human consumption. Learn some interesting facts about methanol including its chemical properties and structure.

What is Methanol?

This is a pretty cool fact about methanol, it is naturally found in wood. Recognized as a type of alcohol it is also referred to as a 'woody alcohol.' Volcanic gases and even certain fuels contain methanol. Did you know trace amounts of methanol are found in our fruits, vegetables, and fruit juices? This is true as it is naturally found in some of these items. Considering that to a certain degree, methanol is toxic to our health, it is quite surprising to know this chemical is naturally found in our food. Let's learn more about the chemical properties and structure of methanol before addressing its uses and health hazards.

Methanol is a simple alcohol that contains a methyl group (carbon atom and 3 hydrogen atoms) bonded to an alcohol (OH) group. The chemical structure of methanol is shown in diagram 1. A colorless, clear liquid, it is known to have a distinct odor. The chemical formula for methanol is CH3OH. Its molar mass is 32.04 g/mol. The molar mass of a chemical is a type of physical property (diagram 2) . It is the relationship between the mass of a substance (in grams) and its amount (mols). Several safety measures are in place to protect those individuals who may be working with methanol. One primary reason is regarding fire hazards. Methanol is considered to be highly flammable and volatile. Keep this one aspect in mind regarding volatility. The more volatile a substance is the lower its boiling point will be. Methanol has a boiling point of 64.6C. To put this in perspective, the boiling point of water is 100C. With such a low boiling point it makes perfect sense why methanol is so volatile!

Diagram 1: Chemical Structure Of Methanol
methanol

Diagram 2: Molar Mass Equation
molar mass

The density of liquid methanol is 791.80 kg/m³. Density refers to the relationship between the mass of a substance (i.e. size) and how much space it will occupy (i.e. volume). The formula for density, shown in diagram 3 explains this relationship. Now let's compare this to the density of water which is approximately 999.97kg/m³. What does this all mean? Because methanol is less dense (a smaller number) than water (a larger number) this essentially means methanol will 'float' on top of water (diagram 4a). But wait a second, if you decided to test this you will actually see water and methanol mix quite well with one another. Now why would this occur? The answer lies within the polarity of both molecules (diagram 4b). Methanol and water are polar liquids. Following the solubility rule 'like dissolves like,' methanol really enjoys interacting with other polar substances like water. Thus, although it may be slightly less dense this physical property doesn't stop methanol from mixing well with water (or water based solutions).

Diagram 3: Density Formula
density

Diagram 4: Explanation Of The Density And Polarity Properties Of Methanol
methanol density

Interesting Facts Concerning Methanol

Many industrial products contain methanol. From windshield wiper fluid and pesticide spray to paints and adhesives, methanol is widely used in the production of commercial items. Even cigarette smoke has been shown to contain traces of methanol.

Methanol is used to make artificial sweeteners. Don't be surprised when you read the back of your favorite artificial sweetener packet and see methanol as an ingredient. These sweeteners such as Equal and NutraSweet contain methanol due to its physical property of having a sweet taste.

At sufficient doses methanol is poisonous. This is surely not the type of alcohol suitable for human consumption. Ingesting just a few teaspoons of methanol has been linked to blindness. Eek that is not good! Found in our fruits and vegetables or commercial products our exposure to methanol, via these sources, occurs at such a low dose that adverse health effects are not typical.

You want an alternative fuel, look into using methanol. Racing cars commonly use methanol as a fuel choice over traditional gasoline. The ability to power a race car at high speeds in a short amount of time makes methanol the perfect fuel to use.

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