Properties and characteristic properties

Properties

Properties are aspects that can be used to describe a particular substance. For example, I can describe water to be as liquid, clear, odorless and tasteless. In this case, I chose to talk about the following properties of water:

  • State
  • Clarity or color
  • Odor
  • Taste

You can choose to describe different substances using different properties. Let’s see what we can say about a sheet of white paper. It is malleable (also known as pliable), white color, odorless, thin, floats on water, absorbs water, does not react with water, etc. So the properties I chose to talk about were:

  • Malleability
  • Color
  • Odor
  • Thickness
  • Buoyancy (how well something floats on water)
  • Water absorbance
  • Water reactivity

If you do it backwards however, we see that we run into some trouble. For example, let’s play a game. I want you to guess who I’m thinking about.

I’m thinking about a person who wears glasses. Take a minute to think about it and if you’re reading this by yourself, say the name of the person out loud 🙂

Ok done guessing? Great! I was thinking of Dumbledore from the Harry Potter series. Did you guess correctly? No?

Alright, so I admit that the property I chose to describe the person I was thinking about wasn’t the most specific. How about if I said I’m thinking of someone old and with glasses. Still not that specific. Many people can be old and many people can be old and wearing glasses. Ok, now let’s continue with chemistry.

I’m thinking about a substance that is clear. Did you guess glass? If so then you got it right! However, a clear substance is a property that is very generic or unspecific. It can be used to describe water, glass, diamond and other substances.

To avoid issues like this, we choose to talk about something called characteristic properties. Characteristic properties are properties that are unique to a single substance. For example, we can say that water has a density of exactly 1g/mL. The only substance that has this density is water. Nothing else!

There are many such properties that we can talk about, such as:

  • Density
  • Solubility (how well something can dissolve in water)
  • Specific heat capacity (how well a substance retains heat)
  • Index of refraction (how well a substance bends light)
  • Boiling point (the temperature at which the substance goes from gas to liquid)
  • Melting point (the temperature at which a substance goes from solid to liquid)
  • Viscosity (the fluid-ness of a substance)
  • Luster (how well a substance reflects light)
  • Conductivity (how well a substance allows electrons to flow through)

Every pure substance that you can imagine has a unique density, solubility, specific heat capacity, etc. This can be a great way to identify a substance. Please note that the ones mentioned above are not the only properties to be used to characterize a particular substance. There are many more.

Why is it important to know these properties? Well, in reality, we use substances for everything. For example, we use different metals to build things, and knowing how malleable a particular metal is will help determine what the beams in a building should be made of. Or knowing how something reacts to heat might influence our decision if we decide to make pots and pans out it. Knowing that CO2 can be harmful to the environment helps us learn ways to do things without producing CO2. These are just a few examples, but there are many many more!