What burning makes: oxides
A teacher burns a little sulfur. A gas rises. What kind of gas is it?
- Sulfur burns in air. Its oxide is a gas.
- In water, the gas turns blue litmus (a colour-test paper) red. It is acidic.
- Magnesium ribbon burns with a white flame too bright to look at. White ash is left.
- The ash is an oxide. In water it turns red litmus blue. It is basic.
It is an acidic gas, sulfur dioxide.
The new word
- Oxide — what a substance makes when it joins with oxygen.
Dissolve means mix evenly into water.
The rule
A metal's oxide is usually basic. A non-metal's oxide is usually acidic. Litmus in water can show which, if the oxide dissolves.
Sulfur dioxide is acidic. Magnesium oxide is basic. Carbon dioxide from your breath makes a weak acid in water.
Your teacher shows burning with eye protection. Never burn anything yourself. Never look at the flame or breathe the gas.
Watch out!
Usually is not always. Aluminium oxide can act as an acid and as a base. Carbon monoxide is a non-metal oxide that is neutral. Neutral means neither acidic nor basic.
Now try it. Pick an oxide. Guess which paper changes. Then see.
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