Question:
How is cream separated from milk ?
Answer:
Milk is a suspension of tiny droplets of oil (cream) in a watery liquid. The process of centrifugation is used in dairie, Separate cream from, milk. The milk is put in a closed container in big centrifugation. When the centrifuge machine is switched on, the milk is rotated (or spun) at a very high speed in its container. Due to this, the milk separates into 'cream' and 'skimmed milk The cream, being lighter,flots over the skimmed milk .It can be removed.
Is Matter Around Us Pure?
Q 1.
What is the general name of the process by which tea-leaves are separated from prepared tea ?
Q 2.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 3.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 4.
Name one pair of liquids which can be separated by using a separating funnel.
Q 5.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 6.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 7.
Define Brownian movement in colloids.
Q 8.
Give two reasons for supposing that water is a compound and not a mixture.
Q 9.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 10.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 11.
What are non-aqueous solutions?
Q 12.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293K. Find its concentration at this temperature.
Q 13.
Name a non-metal which is a good conductor of electricity.
Q 14.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 15.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 16.
State the differences between compounds and mixtures.
Q 17.
What is saturated solution? Explain with an example.
Q 18.
How are sol, solution and suspension different from each other?
Q 19.
What is meant by saying that metals are malleable and ductile ?
Q 20.
Which of the two will scatter light: soap solution or sugar solution ? Why ?
Q 21.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 22.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 23.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 24.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 25.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 26.
What are different categories of pure substance?
Q 27.
What is an unsaturated solution?
Q 28.
What are different ways to separate solid mixtures?
Q 29.
Who used the term 'element' first time?
Q 30.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 31.
State whether the following statement is true or false : Milk is a pure substance.
Q 32.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 33.
Name the process you would use to separate a mixture of anthracene and copper sulphate ?
Q 34.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 35.
Name the process which is used in milk dairies to separate cream from milk.
Q 36.
How is cream separated from milk ?
Q 38.
What are the characteristics of mixture?
Q 39.
Explain with an example what is a colloid?
Q 40.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 41.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 42.
Name any two solid substances whose mixture can be separated by sublimation.
Q 43.
How will you separate a mixture of chalk powder and water ?
Q 44.
What is a solution? What are the properties of a solution?
Q 45.
Why do fish go in deep waters during day light?
Q 46.
Based on the type of solvent, how solutions are classified?
Q 47.
What are suspensions? Explain with an example.
Q 48.
Winnowing works on what property?
Q 49.
Name the following :
(a) a lustrous liquid metal.
(b) a liquid non-metal
(c) a metal which can be cut with a knife
(d) a non-metal which is good conductor of electricity.
(e) an element which melts when kept on the palm.
(f) the best conductor of heat.
Q 50.
Name the elements are in liquid state at room temperature.
