How Can I Compare and Contrast Mixtures and Pure Substances?

You can compare and contrast mixtures and pure substances by determining if the substance can be separated into homogeneous materials. Determine if the substance can be changed into a different substance as well.

  1. Determine if the mixture is heterogeneous or homogeneous

    A mixture is considered heterogeneous if two or more components can easily be seen and separated. An example of this is oil-and-vinegar salad dressing. If you can see two or more separate components in your mixture, it is heterogeneous. If the mixture appears to be the same throughout, it is considered homogeneous. An example of this is salt water. If the mixture is homogeneous, it is similar to a pure substance.

  2. Separate the components of the mixture

    Distillation is the process to separate components of a homogeneous mixture. First, heat the mixture until a gas begins to form. Next, collect the gas and use cold water to condense the gas back into a liquid. Collect this liquid and compare with the original liquid to determine if it's different.

  3. Determine if the mixture is a pure substance

    If the homogeneous mixture cannot be distilled, consider it a pure substance. Pure substances have physical properties that are not changed if the substance undergoes a chemical change. Physical and chemical properties can be used to distinguish a mixture from a pure substance.