The World of Metals and Non-metals
Metal oxides and non-metal oxides
Watch what happens when magnesium and sulfur burn, and test what they form.
Activity 4.6 (your teacher shows this; wear eye protection): clean a 3–4 cm magnesium ribbon with sandpaper, hold it with tongs and light it. It burns with a dazzling white flame and turns into a white powder. The powder is magnesium oxide, made when magnesium joins with oxygen from the air.
Mix the powder with a few drops of warm water and test it. It turns red litmus blue, so it is basic. Oxides of metals are generally basic.
Sodium is a hot-tempered metal. It reacts so fiercely with oxygen and water, giving out a lot of heat, that it can catch fire. So it is stored under kerosene, away from air and moisture.
Activity 4.7 (teacher only, in a well-ventilated place, because the gas is harmful to breathe): burn sulfur powder in a long-handled deflagrating spoon, lower it into a covered jar, then add water and shake. Burning sulfur makes sulfur dioxide gas. In water it makes sulfurous acid. Test it: it turns blue litmus red, so it is acidic. (Careful in exams: it is sulfurous acid, not sulfuric.)
Activity 4.8: put sulfur powder in plain water. Nothing happens. Non-metals generally do not react with water.
| Magnesium (metal) | Sulfur (non-metal) | |
|---|---|---|
| burns with | dazzling white flame | a blue flame |
| product | magnesium oxide, a white powder | sulfur dioxide, a gas |
| in water | basic: red litmus → blue | acidic (sulfurous acid): blue litmus → red |
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