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.
Name one pair of liquids which can be separated by using a separating funnel.
Q 3.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 4.
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 5.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 6.
What are non-aqueous solutions?
Q 7.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 8.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 9.
How many elements are there which are in gaseous state at room temperature?
Q 10.
State whether the following statement is true or false : Milk is a pure substance.
Q 11.
Who used the term 'element' first time?
Q 13.
What is saturated solution? Explain with an example.
Q 14.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 15.
Name a non-metal which is a good conductor of electricity.
Q 16.
Define a compound. Give two points of evidence to show that sodium chloride is a compound.
Q 17.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 18.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 19.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 20.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 21.
Name the apparatus you would use to separate oil from water.
Q 22.
What is a solution? What are the properties of a solution?
Q 23.
What are the advantages of preparing solutions?
Q 24.
What is an unsaturated solution?
Q 25.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 26.
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 27.
Name the elements are in liquid state at room temperature.
Q 28.
Why solutions do not exhibit Tyndall effect?
Q 29.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 30.
What are pure substances ? Give two examples of pure substances.
Q 31.
Name a metal :
(a) which can be easily cut with a knife
(b) which forms amalgams
©which has not fixed shape
(d) which has a low melting point
(e) which is yellow in colour
Q 32.
A 15% alcohol solution means :
(a)15 mL alcohol and 85 mL water.
(b)15 mL alcohol and 100 mL water.
Choose the correct answer.
Q 33.
Explain what happens when a beam of light is passed through a colloidal solution.
Q 34.
What is meant by the concentration of a solution ?
Q 35.
Name any two solid substances whose mixture can be separated by sublimation.
Q 36.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 37.
How will you separate a mixture of chalk powder and water ?
Q 38.
Name the process which is used in milk dairies to separate cream from milk.
Q 39.
(a) Name the process by which common salt is obtained from sea-water.
(b) Name the process by which common salt is purified.
Q 40.
What are the kinds of mixture?
Q 41.
What are the characteristics of mixture?
Q 42.
State the differences between compounds and mixtures.
Q 43.
What factors affect the solubility of solvent and solute?
Q 44.
Based on the type of solvent, how solutions are classified?
Q 45.
What are suspensions? Explain with an example.
Q 46.
Explain with an example what is a colloid?
Q 47.
What do you mean by strength of the solution?
Q 48.
What are the various methods to express concentration of a solution?
Q 49.
What are different ways to separate solid mixtures?
Q 50.
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
