Elements, Compounds, and Mixtures

The last fundamental topic in Unit 2 is the study of elements, compounds, and mixtures. An element is a type of atom; they are found on the periodic table (ex. iron). A compound is a group of elements bonded together; they have one distinct chemical formula (ex. water – H20). A mixture is a combination of various compounds; it cannot be described by one distinct formula (ex. orange juice).

Today in class students traveled around the room examining seven different substances: water, charcoal, soda, vitamin-C, air, grass, and wood. Using their observational skills and a dash of common sense, they tried to classify each substance as an element, a compound, or a mixture. The results were somewhat surprising.


Only one of the substances was a pure element (charcoal). Only two of the substances were compounds (water and vitamin-C). And just like in real life, most of the substances were actually mixtures… even air! Air is composed of several different compounds (CO2, N2, O2, etc.). And that means that, even though you might not be able to see the differences, it is actually a mixture.

October 23 – Elements, Compounds, and Mixtures (pg216)

This weekend’s HW is the Unit 2 Checkpoint Quiz. To take it, please click here. When you finish, your score will automatically be emailed to Mr. A.

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