Metals show metallic lustre, are generally hard, malleable and ductile. They are good conductors of heat and electricity.
The following activities prove the above points:
1. Aim: Perform an activity to show that metals possess lustre.
Materials required: Copper strip, blade, piece of cloth.
- Take a copper strip which has remained exposed to moisture and atmosphere for a long time. It will have a greenish coating of copper oxide and copper carbonate.
- Rub the strip with a blade patiently for about five minutes.
- Clean the surface with a clean cloth piece.
- We shall find that the surface which was dull earlier become shining red-brown which is the colour of copper.
- The activity proves that metals have lustre.
- All metals have lustre, but the colours might be different.
2. Aim: Perform an activity to prove that metals are malleable (can be beaten into sheets) and ductile (can be drawn into wires).
Materials required: Metals such as the iron, copper, aluminium, hammer.
- Take a small piece of iron metal. Place it on an iron block.
- Strike the iron piece with a hammer about ten times. We observe that the iron piece is flattened into a thin sheet. This property is known as malleability. Most of the metals are malleable. Gold and silver are the most malleable metals.
- Similarly, we find that most metals are ductile, i.e., they can be drawn into wares, using a suitable mechanical device.
- Surprisingly, one gram of gold can be drawn into thin wire measuring two kilometres.
3. Aim: Perform an activity to show that metals are good conductors of heat.
Materials required: Iron stand, clamp, iron wire, pin, wax, burner.
- Take long straight ironware about 30 cm long.
- Clamp it to an iron stand as shown.
- Fix a pin to the free end of the wire using wax.
- Heat the wire using a burner near the place where it is clamped.
Experiment Setup Result
- We observe that after some time, the pin that was fixed to the free end of the wire with wax falls down.
- We observe the same with other metals. This is because the wax gets melted because of heat.
- This proves that metals are good conductors of heat. The best conductors of heat are silver and copper. Lead and mercury are comparatively poor conductors of heat.
4. Aim: Perform an activity to show that metals are good conductors of electricity.
Materials required: Battery, bulb, switch, clips, samples of metals.
Set up an electric circuit as shown.
Place a piece of copper metal between the terminals A and B.
We find that the bulb in the circuit glows. This is because the copper metal passes on the current from clip A to clip B.
Setup to Demonstrate Metals are Good Conductors of Electricity➢ Metals are Sonorous
- Metals produce a sound when they strike a hard surface. We express it by saying that metals are sonorous.
- That is why school bells are made of metals.
Question 1:Which property of metals is used for making bells and strings of musical instruments like Sitar and Violin?
Sonorousness is the property of metal by which it makes a sound. Hence, it is used for making bells and strings of musical instruments like Sitar and Violin.
- Substances like carbon, sulphur and iodine are non-metals.
- They are either solids or gas with the exception of bromine which is a liquid.
- Non-metals, in general, do not possess metallic lustre, do not conduct heat and electricity and are not sonorous.
- They are comparatively softer substances.
- Metals, in general, have high melting points. But mercury, gallium and caesium have low melting points and are liquids at room temperature.
- Iodine, a non-metal, shows lustre.
- Diamond, an allotrope of carbon, is the hardest natural substance known. Graphite, another allotrope of carbon, is a conductor of electricity.
- Alkali metals like sodium and potassium (metals) are soft and can be cut with a knife. They have low densities and low melting points.
Note: Elements can be classified as metals and non-metals on the basis of their chemical properties.
Aim: Perform an experiment to decide whether the given substance is a metal or a non-metal.
Materials required: A piece of magnesium ribbon, sulphur powder, pair of tongs, an iron sheet, burner, test tube, blue and red litmus papers.
- Hold the Mg ribbon with a pair of tongs. It burns and forms a white residue.
- Collect the white residue and dissolve it in water in a test tube.
- Dip red litmus paper into it. It turns blue showing that the solution was alkaline. It means metals on burning form basic oxides.
- Now bum sulphur powder on a thick sheet of iron. Collect the fumes produced (SO2) into an inverted test tube over it.
- Immediately add water to the test tube and shake.
- Now dip a blue litmus paper into the solution. It turns red.
- That means the solution in the test tube was acidic.
- That means sulphur, a non-metal on burning forms oxide which is acidic.
- Thus metals form basic oxides, and non-metals form acidic oxides.