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Solutions for Chemistry, Class 7, ICSE
Name a metal:
(a) that is the most malleable
(b) that is brittle
(c) as precious as gold
(d) that can be cut with knife
(e) used in making electric cables
(f) used as a thermometric liquid
(g) that is the best conductor of electricity
(a) Gold
(b) Zinc
(c) Platinum
(d) Sodium
(e) Copper
(f) Mercury
(g) Silver
Name a non-metal that is:
(a) a good conductor of heat and electricity
(b) hardest naturally occurring substance
(c) used to kill germs in water
(d) lustrous
(e) used for filling into electric bulbs
(f) used for cancer therapy
(g) liquid at room temperature
(a) Graphite (a form of carbon)
(b) Diamond (a form of carbon)
(c) Chlorine
(d) Iodine
(e) Argon
(f) Radon
(g) Bromine
Mention two uses of the following metals and non-metals:
(a) Iron
(b) Aluminium
(c) Gold
(d) Oxygen
(e) Iodine
(a) Iron is used for:
(b) Aluminium is used for:
(c) Gold is used for:
(d) Oxygen is used for:
(e) Iodine is used for:
Give reasons:
Magnesium is used in fireworks.
Magnesium burns with a dazzling light so it is used in fireworks.
Give reasons:
Aluminium is used in making aircrafts.
Aluminium is light and when mixed with other metals like Cu, Mg, Mn it becomes stronger so it is used in making aircrafts.
Give reasons:
Copper is used in making electric cables.
Copper is highly ductile and is a very good conductor of heat and electricity, so it is used in making electric cables.
Give reasons:
Graphite is used in the leads of pencils.
Graphite is soft and its layers slip to marks paper black so it is used in the leads of pencils.
Give reasons:
Impure diamond is used to cut glass.
Diamond is the hardest substance so it is used to cut glass.
Give reasons:
Gold is mixed with copper and nickel.
Gold is the most malleable metal and is very soft. To make it harder and cheaper gold is mixed with copper and nickel.
Give reasons:
Tungsten is used in electric bulbs.
It can withstand high temperature and has highest melting point so it is used in electric bulbs.
Name the metals present in the following alloys:
(a) Brass
(b) Bronze
(c) Duralumin
(d) Stainless steel
(a) Copper, zinc
(b) Copper, tin
(c) Aluminium, manganese, magnesium, copper
(d) Iron, chromium, nickel
Give four differences between metals and non-metals with reference to their:
(a) Melting point and boiling point
(b) Conductivity of heat and electricity
(c) Malleability
(d) Solubility in water.
(a) Metals have high melting point and boiling point whereas non-metals have low melting point and boiling point.
(b) Metals are good conductors of heat and electricity but non-metals are bad conductors of heat and electricity.
(c) Metals are mostly malleable while non-metals are not malleable.
(d) Metals are insoluble in water while non-metals can be soluble or insoluble in water.
What are metalloids?
Metalloids are the elements which show some properties of metals and some properties of non-metals. Examples: Silicon(Si), Germanium(Ge), Antimony(Sb).
Give two uses of:
(a) Silicon
(b) Antimony
(c) Tungsten
(d) Germanium
(a) Two uses of silicon are:
(b) Two uses of antimony are:
(c) Two uses of tungsten are:
(d) Two uses of Germanium are:
Fill in the blanks:
(a) The most ductile metal is ............... .
(b) A metal stored in kerosene oil is ............... .
(c) Tungsten metal is a good conductor of ............... .
(d) ............... is a soft metal.
(e) ............... is the hardest compound known to us.
(f) A non-metal used to purify water is ............... .
(g) A metal that gives dazzling effect to crackers when they explode is ............... .
(h) A chemical compound that makes up the striking heads of match sticks is ............... .
(a) Silver
(b) Sodium
(c) electricity
(d) Pure gold
(e) Silicon carbide
(f) Chlorine
(g) Magnesium
(h) Phosphorous sulphide
Match the following:
| Column A | Column B |
|---|---|
| (a) Helium | (1) electric bulb |
| (b) Neon | (2) Thermometer |
| (c) Argon | (3) Semiconductor |
| (d) Germanium | (4) Weather observation balloons |
| (e) Mercury | (5) Advertising signboards |
| Column A | Column B |
|---|---|
| (a) Helium | (4) Weather observation balloons |
| (b) Neon | (5) Advertising signboards |
| (c) Argon | (1) electric bulb |
| (d) Germanium | (3) Semiconductor |
| (e) Mercury | (2) Thermometer |
Write True or False for the following statements:
(a) Silver is used to make electric cables.
(b) Iodine acts as an antiseptic in the form of tincture of iodine.
(c) Sodium can be cut with a knife.
(d) Antimony is a metal.
(e) Sand is an oxide of silicon.
(a) False
Correct Statement — Copper is used to make electric cables.
(b) True
(c) True
(d) False
Correct Statement — Antimony is a metalloid.
(e) True
The noble gas used in advertising signboards is:
Neon
Reason — Neon emits a coloured light when a high voltage current is passed through it, so it is used in advertising signboards.
A metal with melting point less than 50°C is:
Gallium
Reason — Gallium changes into liquid above 30°C i.e. even when placed on palm of hand.
A metal which is neither ductile nor malleable is:
Zinc
Reason — Zinc is neither ductile nor malleable but it is brittle.
Rust is a hydrated oxide of iron which is:
Reddish brown
Reason — Iron when exposed to moist air forms a reddish brown layer known as rust on its surface. Rust is hydrated ferric oxide.
Aluminium is not used to make:
Fireworks
Reason — Aluminium is used to make foils, wires, utensils. Magnesium is used in fireworks as it burns with dazzling light but aluminium does not.
A metalloid used in the manufacture of microchips used in computer is:
Silicon
Reason — Highly pure Silicon is used in the manufacture of microchips used in computer.
A metalloid used to make glass:
Silicon
Reason — Sand which is silicon dioxide, is the principal ingredient of glass.