Q79. How can we separate cream from milk? 

 

Q80. Non-metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable and are coloured.

(a)    Name a lustrous non-metal.

(b)    Name a non-metal which exists as a liquid at room temperature.

(c)    The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.

(d)   Name a non-metal which is known to form the largest number of compounds.

(e)    Name a non-metal other than carbon which shows allotropy.

(f)    Name a non-metal which is required for combustion.

 

Q81. Which of the following are not compounds?

(a) Chlorine gas

(b) Potassium chloride

(c) Iron

(d) Iron sulphide

(e) Aluminium

(f) Iodine

(g) Carbon

(h) Carbon monoxide

(i) Sulphur powder

 

Q82. Arun has prepared 0.01% (by mass) solution of sodium chloride in water. Which of the following correctly represents the composition of the solutions?

(a) 1.00 g of NaCl + 100 g of water

(b) 0.11 g of NaCl + 100 g of water

(c) 0.01 g of NaCl + 99.99 g of water

(d) 0.10 g of NaCl + 99.90 g of water

 

Q83. What are the properties of non-metal?

 

Q84. What is a solution?

 

Q85. During an experiment the students were asked to prepare a 10% (mass/mass) solution of sugar in water. Ramesh dissolved 10 g of sugar in 100 g of water while Sarika prepared it by dissolving 10 g of sugar in water to make 100 g of the solution.

(a) Are the two solutions of the same concentration?

(b) Compare the mass % of the two solutions.

 

Q86. Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do.

 

Q87. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

 

Q88. On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide.

(a) Is this a physical or a chemical change?

(b) Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved.

 

Last modified: Wednesday, 5 May 2021, 11:20 AM