Substances, Mixtures, and Solutions

Substances, Mixtures, and Solutions

Substance: A substance is something that can’t be broken down into simpler parts and physical changes won’t alter its composition. A substance is made of a single compound. For example, water (H₂O) is a substance. No matter what physical processes you put water through (like freezing or boiling), water will remain H₂O.

Mixture: A mixture, on the other hand, is made of different substances that are mixed together that aren’t chemically bonded. Salad dressing is a mixture of different things, like oil, herbs, and lemon juice. A salad is also an example of a mixture.

There are two kinds of mixtures

1. Heterogeneous Mixture: A mixture where the substances aren’t evenly mixed. A salad is an example of a heterogeneous mixture; every bite of a salad is different no matter how many times you mix the salad.
   1. Hetero is Greek for ‘different’, so the mixture has different parts; it’s not all the same.

1. Homogenous Mixture: A mixture where the molecules of each substance are equally mixed, and you can’t see the different parts of the mixture. Sugar that is dissolved in water creates a homogenous mixture--you can’t see the sugar and the water, just a liquid that contains molecules of both.
   1. Homo is Greek for ‘same’, so the mixture is the same throughout.

Sometimes, homogenous mixtures are called solutions. A solution is made of a solute and a solvent.

1. Solute: The substance that is dissolved into the other substance.
2. Solvent: The substance into which the solute dissolves. This substance ‘does’ the dissolving.

For example, some sports drinks are a solution that is made of water (the solvent) and powdered sports drink mix (the solute).