Allen P. answered • 05/08/19
A Real Certified Teacher
Pure substances are both elements and compounds.
Here is why: A compound is a chemical combination of 2 or more elements. Meaning that the atoms (teeny-tiny little things that make up all elements) are combined and cannot be separated without the use of chemicals or electricity. When elements form a compound, they become a new substance. For example, salt is formed when the element of sodium (which is a metal like aluminium), and Chlorine (which is a gas like oxygen) combine. So now that I have a compound of salt, I can consider the compound pure because of 1 simply thing: I cannot split it into a new substance by physical means. I can take the worlds sharpest knife and cut a piece of salt, but now I have 2 pieces of salt. I dont have salt and sugar. All compounds are the same. I can take hydrogen and Oxygen and make water. I cannot physically separate them back to their elements. Only electricity can, so this proves compounds are pure substances. Half of water is still water. Half of 1 grain of salt, is still salt.
Elements are also pure. Name any element: Helium, Iron, Aluminum, etc etc. If tear the aluminum in half, its still aluminum. If I take iron and slice it with a blow torch, its still iron. If I take helium gas out of a balloon, its still helium, even though it has now mixed with the other gas in the air, the helium that was in the balloon is still helium, even though its out the balloon.
Things that aren't pure substances are called mixtures. Mixtures can be separated by physical means. I can get sugar out of sugar water by boiling the water away. I can get rocks out of sand by running it through a filter. I can get iron out of water by using a magnet.
