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.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 3.
What is meant by solute and solvent?
Q 4.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 5.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 6.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 7.
Name one pair of liquids which can be separated by using a separating funnel.
Q 8.
Name the apparatus you would use to separate oil from water.
Q 9.
What is saturated solution? Explain with an example.
Q 10.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 11.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 12.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 13.
What is a solution? What are the properties of a solution?
Q 14.
What are non-aqueous solutions?
Q 15.
What are the various methods to express concentration of a solution?
Q 16.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 17.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 18.
What are the differences and similarities between concentration and solubility?
Q 19.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 20.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 21.
What is an unsaturated solution?
Q 22.
Define Brownian movement in colloids.
Q 23.
Name the elements are in liquid state at room temperature.
Q 24.
Name a metal which is soft and a non-metal which is hard.
Q 25.
What is meant by saying that metals are malleable and ductile ?
Q 26.
What are pure substances ? Give two examples of pure substances.
Q 27.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 28.
What are the kinds of mixture?
Q 29.
Give two reasons for supposing that water is a compound and not a mixture.
Q 30.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 31.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 32.
What are different categories of pure substance?
Q 33.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 34.
Why do fish go in deep waters during day light?
Q 35.
What is Chromatography?
Q 36.
Name a non-metal which is a good conductor of electricity.
Q 37.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 38.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 39.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 40.
Name two properties of a substance to check its purity?
Q 41.
What are suspensions? Explain with an example.
Q 42.
What are the properties of suspensions?
Q 43.
How crystallization is better than evaporation?
Q 44.
Why solutions do not exhibit Tyndall effect?
Q 45.
What is an emulsion? Give examples
Q 46.
State whether the following statement is true or false : Milk is a pure substance.
Q 47.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 48.
A 15% alcohol solution means :
(a)15 mL alcohol and 85 mL water.
(b)15 mL alcohol and 100 mL water.
Choose the correct answer.
Q 49.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 50.
How will you separate a mixture of chalk powder and water ?
