Question:
(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
Answer:
(a)(i)An element is a substance which cannot be split up into two or more simpler substances by the usual chemical methods of applying heat, light or electric energy. For example, hydrogen is an element(ii)A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass.(iii)A mixture is a substance which consists of two or more elements or compounds not chemically combined together.
two compound is water and carbon dioxide,two mixture is air and milk
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.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 3.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 4.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 5.
Name any two solid substances whose mixture can be separated by sublimation.
Q 6.
What are the properties of a colloid?
Q 7.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 8.
What are aqueous solutions?
Q 9.
What is saturated solution? Explain with an example.
Q 10.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 11.
What is a solution? What are the properties of a solution?
Q 12.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 13.
What is meant by solute and solvent?
Q 14.
What are suspensions? Explain with an example.
Q 15.
A solution contains 40 mL of ethyl alcohol mixed with 100mL of water. What is the concentration of the solution in terms of volume by volume percentage?
Q 16.
What are pure substances ? Give two examples of pure substances.
Q 17.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 19.
When we open the cap of a cola drink (or any carbonated beverage), why does excess of bubbles come out?
Q 20.
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 21.
How crystallization is better than evaporation?
Q 22.
Define Brownian movement in colloids.
Q 23.
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 24.
What is an emulsion? Give examples
Q 25.
Name one pair of liquids which can be separated by using a separating funnel.
Q 26.
What are the reasons for separating the constituents of a mixture?
Q 27.
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
Q 28.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 29.
Give two reasons for supposing that water is a compound and not a mixture.
Q 30.
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 31.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 32.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 33.
(a) Name the process by which common salt is obtained from sea-water.
(b) Name the process by which common salt is purified.
Q 34.
On the basis of composition, how matter is classified?
Q 35.
What are the constituents of brass?
Q 36.
State the differences between compounds and mixtures.
Q 37.
What are non-aqueous solutions?
Q 38.
Why air is a mixture not a compound? Give reasons.
Q 39.
What is an unsaturated solution?
Q 40.
What is Chromatography?
Q 41.
How many elements are there which are in gaseous state at room temperature?
Q 42.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 43.
In beaker A, sugar cubes are dissolved into water while in beaker B, crushed cubes are taken. In which beaker the rate of dissolution is faster?
Q 44.
Name a metal which is soft and a non-metal which is hard.
Q 45.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 46.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 47.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 48.
How will you separate iron pins from sand ?
Q 49.
What are the characteristics exhibited by a pure substance?
Q 50.
What are different categories of pure substance?
