Reason: Both of them are made from the same element.
- The assertion is false but the reason is true.
- The assertion is true but the reason is false.
- Both assertion and reason are true and the reason is the correct explanation for the assertion.
- Both assertion and reason are true but the reason is not the correct explanation for the assertion.
- It has a high melting point.
- It cannot reflect light falling on it.
- It is a good conductor of electricity.
- It is used for cutting glasses.
- Low melting point
- Bad conductor of electricity
- Very hard in nature
- Highly malleable
Graphite is a soft lubricant extremely difficult to melt. What is the reason for this anomalous behaviour?
(a) Write two points of difference in the structures of diamond and graphite.
(b) Explain why graphite can be used as a lubricant but diamond cannot.
(c) Explain why diamond can be used in rock drilling equipment but graphite cannot.
(d) State one use of diamond which depends on its 'extraordinary brilliance' and one use of graphite which depends on its being 'black and quite soft'.
A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
(a) How can diamonds be made artificially? How do synthetic diamonds differ from the natural one?
(b) Give any two differences between the properties of diamond and graphite. What causes these differences?
A diamond-toothed saw is usually used for cutting :
(a) steel girders (b) logs of wood (c) marble slabs (d) asbestos sheets
Choose the correct alternative :
(a) In a combined state, carbon occurs as
(b) A crystalline form of carbon is
(i) lamp black
(ii) gas carbon
(c) Graphite is not found in
(d) Diamond is used for
(i) making the electrodes of electric furnaces.
(ii) making crucible for melting metals.
(iii) cutting and drilling rocks and glass.
(iv) making carbon brushes for electric motors.
(e) Carbon forms innumerable compounds because
(i) it has four electrons in its outermost shell.
(ii) it behaves as a metal as well as a non-metal.
(iii) carbon atoms can form long chains.
(iv) it combines with other elements to form covalent compounds.
Name the products formed when :
(a) wood is burnt in the absence of air.
(b) bone is heated in the absence of air.
(c) diamond is burnt in air at 900∘C.
(d) graphite is subjected to high pressure and 3000∘ C temperature.