CBSE Class 7 Science Advanced Chemistry Chemistry in Daily Life Very Short Answer Questions Set 01

Very Short Answer Questions

Question 1. Fill in the blank: Metals combine with other metals to form a homogeneous solid mixture called _______.
Answer:
Alloys
In simple words: Mixing metals and cooling them gives a solid mixture called an alloy.

Teacher's Note:
1. A single alloy name such as brass or bronze is an example.
2. Alloys are usually stronger and resist corrosion better than pure metals.

Question 2. Fill in the blank: The process of coating zinc on an iron surface is called _______.
Answer:
Galvanization
In simple words: Putting a zinc coat on iron to stop rust is galvanization.

Teacher's Note:
1. Hot iron sheets are dipped in molten zinc.
2. Zinc is more reactive, so it protects the iron.

Question 3. Fill in the blank: The alloy formed from gold and mercury is called _______.
Answer:
Gold amalgam
In simple words: An alloy of any metal with mercury is called an amalgam.

Teacher's Note:
1. Gold and silver amalgams are used to fill teeth.
2. Mercury dissolves almost all metals.

Question 4. Fill in the blank: _______ is used as a solid lubricant for machine parts.
Answer:
Graphite
In simple words: Graphite is slippery and does not char, so it can lubricate hot machine parts.

Teacher's Note:
1. Ordinary oils burn or char in very hot parts.
2. Graphite withstands heat well.

Question 5. Fill in the blank: Iodine in a mixture of potassium iodide solution and alcohol is called _______.
Answer:
Tincture of iodine
In simple words: This mixture is the tincture of iodine, used as a germicide on wounds.

Teacher's Note:
1. Iodine itself does not dissolve in water but does in alcohol.
2. Tincture means a solution in alcohol.

Question 6. Fill in the blank: Zincite is obtained by heating _______.
Answer:
Zinc carbonate
Zinc carbonate on strong heating gives zinc oxide, \(\ce{ZnCO3 -> ZnO + CO2}\).
In simple words: Strong heating of zinc carbonate gives zinc oxide (zincite) and carbon dioxide.

Teacher's Note:
1. The reaction is \(\ce{ZnCO3 -> ZnO + CO2}\).
2. Zinc oxide is used in paints.

Question 7. Fill in the blank: The chemical formula of plaster of Paris is ______.
Answer:
\(\ce{CaSO4.1/2H2O}\)
In simple words: Plaster of Paris is calcium sulphate with half a molecule of water of crystallization.

Teacher's Note:
1. It is made by heating gypsum, \(\ce{CaSO4.2H2O}\).
2. Half a water molecule is written as ½ or 1/2.

Question 8. Fill in the blank: The major component of natural gas is ______.
Answer:
Methane (\(\ce{CH4}\))
In simple words: Natural gas is mostly methane.

Teacher's Note:
1. Methane is also the main part of biogas.
2. It is the simplest hydrocarbon.

Question 9. Fill in the blank: _______ is used for filling weather observation balloons.
Answer:
Helium
In simple words: Helium is very light and does not burn, so it is used to fill weather balloons.

Teacher's Note:
1. It is the second lightest element.
2. Being inert, it is safe.

Question 10. Fill in the blank: Bakelite is an example of _______ plastic.
Answer:
Thermosetting
In simple words: Bakelite sets hard on heating and cannot be softened again.

Teacher's Note:
1. Thermosetting plastics cannot be reused.
2. Electric switches are often bakelite.

Teacher's Note:
1. Take each metal and recall its row in the metals table.
2. Lead has two matches here.

Teacher's Note:
1. Electrical switches are brass, not bronze: see the alloys table.
2. Household utensils have three suitable alloys.

Teacher's Note:
1. Use the types-of-glass table.
2. Lime glass has two ingredients in Column B.

Question 14. Mention some specific properties of metals.
Answer:
Metals show lustre (shine), tensile strength, conductivity of heat and electricity, malleability and ductility.
In simple words: Metals shine, conduct, are strong, and can be beaten into sheets or drawn into wires.

Teacher's Note:
1. Malleable means can be hammered into sheets; ductile means can be drawn into wires.
2. These properties decide the uses of metals.

Question 15. Name two metals which find application in ayurvedic medicine.
Answer:
Gold and silver.
In simple words: Both precious metals are used in ayurvedic medicines.

Teacher's Note:
1. Their compounds are also used as medicines.
2. Gold and silver also fill teeth.

Question 16. Name the metal which is extensively used in a printed circuit board.
Answer:
Copper.
In simple words: Copper conducts well and is used for the circuit tracks.

Teacher's Note:
1. Copper is the second best conductor.
2. Zinc cannot be used since it is brittle.

Question 17. Why is graphite used as a major component in pencil lead?
Answer:
Graphite is soft, so it leaves an impression on paper when rubbed.
In simple words: Graphite is soft and leaves marks on paper.

Teacher's Note:
1. Clay is mixed in to give the lead the right hardness.
2. More clay means a harder pencil.

Question 18. Name one compound of silver which is used for cloud seeding.
Answer:
Silver iodide.
In simple words: Silver iodide is used for artificial rain.

Teacher's Note:
1. Silver nitrate can also be used.
2. Cloud seeding gives particles on which water drops form.

Question 19. Which element is used in the manufacture of insecticides and pesticides like DDT and BHC?
Answer:
Chlorine.
In simple words: Chlorine is needed to make DDT and BHC.

Teacher's Note:
1. Chlorine also makes bleaching powder and hydrochloric acid.
2. It also sterilizes drinking water.