You are given a hammer, a battery, a bulb, wires and a switch.
$(a)$ How could you use them to distinguish between samples of metals and non-metals ?
$(b)$ Assess the usefulness of these tests in distinguishing between metals and non-metals.
$(a) $ With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is malleable), then it is a metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and a switch to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.
$(b)$ The above tests are useful in distinguishing between metals and non-metals as these are based on the physical properties. No chemical reactions are involved in these tests.
What are amphoteric oxides? Give two examples of amphoteric oxides.
Give reasons : Sodium, potassium and lithium are stored under oil.
$(i)$ Write the electron-dot structures for sodium. oxygen and magnesium.
$(ii)$ Show the formation of $Na _{2} O$ and $MgO$ by the transfer of electrons.
$(iii)$ What are the ions present in these compounds ?
Give reasons : Platinum, gold and silver are used to make jewellery.
Give reasons : Carbonate and sulphide ores are usually converted into oxides during the process of extraction.