Question:
What are the properties of a colloid?
Answer:
Properties of a colloid are:
- Heterogeneous nature: Colloid or Sol is heterogeneous in nature i.e. it can be seen only with a powerful microscope.
- Particle Size: Colloid particle size lies between 1nm (10-9 m) to 100 nm (10-7 m)
- Separation of colloidal particles by filtration: Colloidal particles cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation.
- Brownian Motion: When seen under microscope, the colloidal particles in a colloid are seen to be moving in a random fashion, called Brownian motion.
- Stability: They do not settle down when left undisturbed, that is, a colloid is quite stable.
- Tyndall effect: Colloid exhibit Tyndall effect. When a light is passed through sol kept in dark room, the path of light beam is visible. It is due to scattering of light by colloidal particles and this effect is called Tyndall effect.
- Electrophoresis: Man colloidal particles may have electrical charge (+ve or -ve) on them. When an electric current passes through a sol, colloid particles move towards opposite charged electrodes. This process is called electrophoresis.
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.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 3.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 4.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 5.
Name one pair of liquids which can be separated by using a separating funnel.
Q 6.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 7.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 8.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 9.
What are non-aqueous solutions?
Q 10.
What is saturated solution? Explain with an example.
Q 11.
Define Brownian movement in colloids.
Q 12.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 13.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 14.
What is meant by saying that metals are malleable and ductile ?
Q 15.
What are pure substances ? Give two examples of pure substances.
Q 16.
Give two reasons for supposing that water is a compound and not a mixture.
Q 17.
What is meant by solute and solvent?
Q 18.
What is an emulsion? Give examples
Q 19.
Name a non-metal which is a good conductor of electricity.
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 an unsaturated solution?
Q 23.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 24.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 25.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 26.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 27.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 28.
State the differences between compounds and mixtures.
Q 29.
What is a solution? What are the properties of a solution?
Q 30.
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
Q 31.
Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk
Q 32.
What is supersaturated solution?
Q 33.
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 34.
What are different ways to separate solid mixtures?
Q 35.
What are the reasons for separating the constituents of a mixture?
Q 36.
What is Chromatography?
Q 37.
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 38.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 39.
(a) What is meant by (i) elements (ii) compounds, and (iii) mixtures ? Write down the names of two elements,two compounds and two mixtures.
(b) Classify the following into elements,
compounds and mixtures :
Marble,
Air,
Gold,
Brass,
Sand,
Diamond,
Graphite,
Petroleum,
Common salt,
Sea-water,
Chalk
Q 40.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 41.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 42.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 43.
Name any two solid substances whose mixture can be separated by sublimation.
Q 44.
What are the kinds of mixture?
Q 45.
What are aqueous solutions?
Q 46.
Why air is a mixture not a compound? Give reasons.
Q 47.
What are the advantages of preparing solutions?
Q 48.
Explain with an example what is a colloid?
Q 49.
What are the various methods to express concentration of a solution?
Q 50.
Who used the term 'element' first time?
