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C3 - Physical and Chemical Properties

I can list the properties of a substance or object and classify them as physical properties or chemical properties

Chemists Study the Properties of Matter

Chemistry is the study of matter and the changes that matter undergoes. In general, chemists are interested in both characteristics that you can test and observe, like a chemical’s smell or color, and characteristics that are far too small to see, like what the oxygen you breathe in or the carbon dioxide you breath out looks like under a microscope 1,000 times more powerful than any existing in the world today.

What kinds of properties do chemists actually measure in the laboratory? Well, you can probably guess a few. Imagine that you go to dinner at a friend’s house and are served something that you don’t recognize – what types of observations might you make to determine exactly what you’ve been given? You might smell the food. You might note the color of the food. You might try to decide whether the food is a liquid or a solid because if it’s a liquid, it’s probably soup or a drink. The temperature of the food could be useful if you wanted to know whether or not you’d been served ice cream! You could also pick up a small amount of food with your fork and try to figure out how much it weighs – a light dessert might be something like an angel cake, while a heavy dessert is probably a pound cake. The quantity of food you’ve been given might be a clue too. Finally, you might want to know something about the food’s texture – is it hard and granular like sugar cubes, or soft and easy to spread, like butter?

Believe it or not, the observations you are likely to make when trying to identify an unknown food are very similar to the observations that a chemists makes when trying to learn about a new material. Chemists rely on smell, color, state (that is, whether it is a solid, liquid or gas), temperature, volume, mass (which is related to weight, as you’ll discover in a later section), and texture. There is, however, one property you might use to learn about a food, but that you should definitely not use to learn about a chemical - taste!

Measurements of certain properties helped early scientists to develop theories about the chemical structure of matter on a scale much smaller than they could ever hope to see. You’ll also learn how these theories, in turn, allow us to make predictions about new materials that we haven’t even created yet.

Lesson Summary

  • With improved understanding of chemistry comes the ability to design new and useful materials, like plastics and semiconductors.
  • Chemists can’t actually see the underlying structure of most materials. As a result, they measure properties that they can see or observe and use this evidence to develop theories that explain how chemicals are organized on a sub-microscopic (smaller than you can see with a microscope) scale.
  • Some of the physical properties that scientists observe pertain to state (solid, liquid, or gas), temperature, volume, mass, and texture.
  • Chemists also study the changes that different materials undergo; this can give them valuable information about the chemicals involved.