This is an example of a pure substance. In this case it is the element lithium.

Lithium reacting with oxygen in air.

After the movie has completely played. Grab the horizontal scroll bar and move it back and forth to see how the newly exposed surface of lithium atoms changes color as they react with oxygen. Also notice that lithium is harder to cut compared to the other metals (called alkali metals) in this group.

This is an example of a two pure substance, carbon dioxide, CO₂ and magnesium. Carbon dioxide is a compound and magnesium is an element.

Initially they are a heterogeneous mixture. But after the the magnesium is ignited using the bunsen burner a chemical change occurs forming magnesium oxide and some carbon.

Here is a mixture of two pure substances. A compound, water, and the element iodine.

What do you see happening when the two substances are mixed?

Do you see a reaction?

If no reaction occurs is this an example of a heterogeneous or homogeneous mixture?

Here is a mixture of two pure substances. A compound, carbon tetrachloride, and the element iodine.

What do you see happening when the two substances are mixed?

Do you see a reaction?

If no reaction occurs is this an example of a heterogeneous or homogeneous mixture?

Here is a mixture of two liquids. Heterogeneous or homogeneous?

Here is a mixture of two liquids. Heterogeneous or homogeneous?

Hmmmm, very interesting. What is going on here?

Whoa!!

Mixtures and reactions

This reaction is called the thermite reaction. The reactants are Fe₂O₃ and Al.

This is the reaction betweeen Mg and Br₂.

In this example the element lithium is added to the compound water.

Do you see a reaction?

What is happening to the two substances that were mixed?

In this example the element sodium is added to the compound water.

Do you see a reaction?

What is happening to the two substances that were mixed?

An explosion when water freezes