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You are provided with a mixture containing sand, iron filings, ammonium chloride and sodium chloride. Describe the procedures you would use to separate these constituents from the mixture?

Answer: The majority of the time, the substances we encounter are not in their purest form. They are, in fact,... View Article

During an experiment the students were asked to prepare a 10% (Mass/Mass) solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water while Sarika prepared it by dissolving 10g of sugar in water to make 100g of the solution. (a) Are the two solutions of the same concentration (b) Compare the mass % of the two solutions.

Answer: Mass % = Mass of solute Mass of solute + Mass of solvent ×100 Solution made by Ramesh Mass... View Article

Classify each of the following, as a physical or a chemical change. Give reasons. (a) Drying of a shirt in the sun. (b) Rising of hot air over a radiator. (c) Burning of kerosene in a lantern. (d) Change in the colour of black tea on adding lemon juice to it. (e) Churning of milk cream to get butter.

Answer: Physical change – A substance is said to undergo a physical change when only the physical properties such as... View Article

A group of students took an old shoe box and covered it with a black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a beaker/tumbler in the box as shown in the Fig. They were amazed to see that milk taken in the tumbler was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it? (a) Explain why the milk sample was illuminated. Name the phenomenon involved. (b) Same results were not observed with a salt solution. Explain. (c) Can you suggest two more solutions which would show the same effect as shown by the milk solution?

Answer: (a) Milk is a colloidal substance. Particulate matter present in the milk makes the light scatter which results in... View Article

A child wanted to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in Fig. The filter paper was removed when the water moved near the top of the filter paper. (i) What would you expect to see, if the ink contains three different coloured components? (ii) Name the technique used by the child. (iii) Suggest one more application of this technique.

Answer: (i) If the ink has three different coloured components, the filter paper will have spots of different colours at... View Article

Iron filings and sulphur were mixed together and divided into two parts, ‘A’ and ‘B’. Part ‘A’ was heated strongly while Part ‘B’ was not heated. Dilute hydrochloric acid was added to both the Parts and evolution of gas was seen in both the cases. How will you identify the gases evolved?

Answer: Part A: When iron filings and sulphur powder are mixed and heated, they undergo a chemical reaction and form... View Article

Can a solution be heterogeneous?

Answer: No, a solution cannot be heterogeneous. A solution is a one-phase mixture that is homogeneous. A solute is a substance... View Article

A solution is always a liquid. Comment.

Answer: The solution is usually a liquid, but not always. It might also include a mixture of two solids like... View Article

Under which category of mixtures will you classify alloys and why?

Answer: An alloy is a homogenous mixture of two or more elements. Elements can be two metals or metal with... View Article

Fractional distillation is suitable for separation of miscible liquids with a boiling point difference of about 25 K or less. What part of fractional distillation apparatus makes it efficient and possess an advantage over a simple distillation process. Explain using a diagram.

Answer: Fractional distillation is a kind of distillation wherein miscible liquids are separated. Repeated distillations and condensations are used in... View Article

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

Answer: Elements – Elements constitute the simplest chemical substances in which all the atoms are exactly the same. Elements are... View Article

Classify the substances given in Fig. into elements and compounds

Answer: Elements – Elements constitute the simplest chemical substances in which all the atoms are exactly the same. Elements are... View Article

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.

Answer: (a) Iodine is a lustrous non-metal. (b) Bromine is liquid at room temperature (c) Graphite is an allotropic form... View Article

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

Answer: Physical change – A substance is said to undergo a physical change when only the physical properties such as... View Article

Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain.

Answer: Since water is a universal solvent and alcohol is an organic solvent, they are miscible liquids that cannot be... View Article

Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

Answer: It will be a pure substance because the chemical composition of sugar crystals derived from sugarcane or beetroot will... View Article

When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is due to the of light by milk and the phenomenon is called . This indicates that milk is a __ solution.

Answer: When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is... View Article

A mixture of two or more miscible liquids, for which the difference in the boiling points is less than 25 K can be separated by the process called______.

Answer: A mixture of two or more miscible liquids, for which the difference in the boiling points is less than... View Article

A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time. The upper layer in the separating funnel will be of and the lower layer will be that of .

Answer: A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time.... View Article

Ice, water and water vapour look different and display different properties but they are __ the same.

Answer: Ice, water and water vapour look different and display different physical properties but they are chemically the same. States of... View Article

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