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.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 4.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 5.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 6.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 7.
What are non-aqueous solutions?
Q 8.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 9.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 10.
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 11.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 12.
Give two reasons for supposing that water is a compound and not a mixture.
Q 13.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 14.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 15.
What is saturated solution? Explain with an example.
Q 16.
Define Brownian movement in colloids.
Q 17.
Who used the term 'element' first time?
Q 18.
State whether the following statement is true or false : Milk is a pure substance.
Q 19.
Name a non-metal which is a good conductor of electricity.
Q 20.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 21.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 22.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 23.
Name any two solid substances whose mixture can be separated by sublimation.
Q 24.
What are the kinds of mixture?
Q 25.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 26.
Name the elements are in liquid state at room temperature.
Q 27.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 28.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 29.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 30.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 31.
What are different categories of pure substance?
Q 32.
Name two properties of a substance to check its purity?
Q 34.
What are the characteristics of mixture?
Q 35.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 36.
What is meant by solute and solvent?
Q 37.
What are the advantages of preparing solutions?
Q 38.
What is an unsaturated solution?
Q 39.
What are suspensions? Explain with an example.
Q 40.
What are different ways to separate solid mixtures?
Q 41.
How many elements are there which are in gaseous state at room temperature?
Q 42.
Name a metal which is soft and a non-metal which is hard.
Q 43.
What are pure substances ? Give two examples of pure substances.
Q 44.
Define a compound. Give two points of evidence to show that sodium chloride is a compound.
Q 45.
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 46.
Which of the two will scatter light: soap solution or sugar solution ? Why ?
Q 47.
What is the most common way of expressing the concentration of a solution ?
Q 48.
A 5 per cent sugar solution means that:
(a)5 g of sugar is dissolved in 95 g of water.
(b)5 g of sugar is dissolved in 100 g of water.
Choose the correct answer.
Q 49.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 50.
Which of the following is a sol ?
Shaving cream,
Milk,
Fog,
Soap solution,
Hairspray
