Question:
(a) What is a physical change ? Give two examples of physical changes.
(b) What is a chemical change ? Give two examples of chemical changes.
Answer:
(a)Physical changes :-1 No new substancc is formed in a physical change.
2. A physical change is a temporary change.
3. A physical change is easily reversible.
4. Very little heat (or light) energy is usually absorbed or given out in a physical change.
5. The mass of a substance does not alter in a physical change. :-1.A new substance is formed in a chemical change.
2.A chemical change is a permanent change.
3.A chemical change is usually irreversible.
4.A lot of heat (or light) energy is absorbed or given out in a chemical change.
5.The mass of a substance does alter in a chemical change.
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.
What are the properties of a colloid?
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.
What is saturated solution? Explain with an example.
Q 6.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 7.
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 8.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 9.
What is a solution? What are the properties of a solution?
Q 10.
What is meant by solute and solvent?
Q 11.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 12.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 13.
What are the reasons for separating the constituents of a mixture?
Q 14.
Who gave the first explanatory definition of 'element'?
Q 15.
Name a metal which is soft and a non-metal which is hard.
Q 16.
(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 17.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 18.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 19.
What are non-aqueous solutions?
Q 20.
What is an unsaturated solution?
Q 21.
What is Chromatography?
Q 22.
Name a non-metal which is a good conductor of electricity.
Q 23.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 24.
Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk
Q 25.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 26.
Name the apparatus you would use to separate oil from water.
Q 27.
What is meant by a pure substance?
Q 28.
Based on the type of solvent, how solutions are classified?
Q 29.
Based on the amount of solute in the given solution, how solutions are classified?
Q 30.
What are aqueous solutions?
Q 31.
When we open the cap of a cola drink (or any carbonated beverage), why does excess of bubbles come out?
Q 32.
Why air is a mixture not a compound? Give reasons.
Q 33.
What are the various methods to express concentration of a solution?
Q 34.
What are different ways to separate solid mixtures?
Q 35.
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 36.
What is an emulsion? Give examples
Q 37.
State whether the following statement is true or false : Milk is a pure substance.
Q 38.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 39.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 40.
What are pure substances ? Give two examples of pure substances.
Q 41.
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 42.
What are the characteristics exhibited by a pure substance?
Q 43.
What are suspensions? Explain with an example.
Q 44.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 45.
Describe sieving method.
Q 46.
Who used the term 'element' first time?
Q 47.
Give two reasons for supposing that water is a compound and not a mixture.
Q 48.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 49.
Fill in the following blanks :
(a)Milk is a.........solution but vinegar is a.......solution.
(b)A colloid is a........mixture and its components can be separated by the technique known as........
Q 50.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
