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.
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.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 7.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 8.
Give two reasons for supposing that water is a compound and not a mixture.
Q 9.
What are non-aqueous solutions?
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.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 12.
Define Brownian movement in colloids.
Q 13.
Name a non-metal which is a good conductor of electricity.
Q 14.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 15.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 16.
State the differences between compounds and mixtures.
Q 17.
What is saturated solution? Explain with an example.
Q 18.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 19.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 20.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 21.
What are different categories of pure substance?
Q 22.
What are the kinds of mixture?
Q 23.
How are sol, solution and suspension different from each other?
Q 24.
What are different ways to separate solid mixtures?
Q 25.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 26.
State whether the following statement is true or false : Milk is a pure substance.
Q 27.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 28.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 29.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 30.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 31.
Name the apparatus you would use to separate oil from water.
Q 32.
How is cream separated from milk ?
Q 33.
What is meant by solute and solvent?
Q 34.
Explain with an example what is a colloid?
Q 35.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 36.
Winnowing works on what property?
Q 37.
Name the elements are in liquid state at room temperature.
Q 38.
Who used the term 'element' first time?
Q 39.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 40.
What is meant by saying that metals are malleable and ductile ?
Q 41.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 42.
What are pure substances ? Give two examples of pure substances.
Q 43.
(a) What is a physical change ? Give two examples of physical changes.
(b) What is a chemical change ? Give two examples of chemical changes.
Q 44.
Name the process you would use to separate a mixture of anthracene and copper sulphate ?
Q 45.
Name any two solid substances whose mixture can be separated by sublimation.
Q 46.
What are the characteristics of mixture?
Q 47.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 48.
What is a compound? Give an example.
Q 49.
What is a solution? What are the properties of a solution?
Q 50.
Why air is a mixture not a compound? Give reasons.
