Is matter around us pure Worksheet-7

Is matter around us pure Worksheet-7

11. A shining thick liquid is often used in glass thermometers. Name it.

A. Cesium          B. Gallium         C. Mercury        D. Bromine

12. A ______ knife is quite often used for cutting glass.

A. Diamond      B. Silicon           C. Fullerene      D. Carbon fibre

13. Is fresh air which we breathe in, a pure substance?

A. Yes                 B. No                  C. Depends on the area

14. The purity of a pure chemical compound in the solid state can be checked by _______.

A. Measuring its density and comparing it with the standard density

B. Determining its melting point experimentally and comparing it with standard melting point value

C. Determining the boiling point of its aqueous solution experimentally and comparing it with standard boiling point value

D. Determining its refractive index and comparing it with standard refractive index value

15. A hard substance when hit with a wooden bar produces a tinkling sound. It is a ____

A. Metal             B. Non-metal    C. Metalloid      D. Plastic

16. Brass is a mixture and not a compound as______.

A. It shows the properties of both copper and zinc

B. The constituents can be separated

C. It does not have sharp M.P.

17. To the already prepared solution of a 'solute A prepared in water, a small amount of A' is added. However, it does not dissolve. What does it indicate ?

A. Solution is saturated

B. Solution is unsaturated

C. Homogeneous mixture

D. Heterogeneous mixture

18. Classify the following as homogeneous and heterogeneous mixtures :

(a)Copper sulphate solution

(b)A suspension of chalk in water

(c)Dust storm

(d)A dilute solution of alcohol in water.

A. A and b homogeneous mixture, c and d heterogeneous mixture

B. A and c heterogeneous mixture, b and d homogeneous mixture

C. A and d heterogeneous mixture, b and c homogeneous mixture

D. A and d homogeneous mixture, b and c heterogeneous mixture

19. What is the range of the size of the particles of dispersed phase in a colloidal solution ?

A. 1 nm -100 nm                           B. 1 nm – 10 nm

C. 10 nm – 100 nm                      D. >100nm

20. When a beam of light was passed through the solution of a substance A' dissolved in water, the path of light could be seen. Predict the nature of the solution.

A. True solution

B. Colloidal solution

C. Suspension

Answer:

11. C

Explanation: The shining liquid is mercury. It is used in glass thermometers as it does not stick to glass.

12. A

Explanation: Diamond is probably the hardest substance known. Therefore, a knife made from a special type of diamond is used for cutting glass.

13. B

Explanation: Air is a mixture of gases and not a pure substance.

(e.g., nitrogen, oxygen, carbon dioxide, water vapours etc.)

14. B

Explanation: The purity of a pure chemical compound can be checked by finding its melting point experimentally and by comparing it with its standard melting point value available in the form of tables. In case, the two values are nearly the same, the substance is pure. Otherwise, it is not.

15. A

Explanation: The hard substance is a metal. Actually metals are sonorous and produce tinkling sound when bent.

16. C

Explanation: Brass does not have a sharp melting point. This shows that it is not a compound. It is a homogeneous mixture of copper and zinc and is called alloy.

17. A

Explanation: This indicates that the solution of the substance A' in water is saturated i.e. no more solute can be dissolved in it.

18. D

Explanation: (a) homogeneous (b) heterogeneous (c) heterogeneous (d) homogeneous.

19. A

Explanation: It ranges from 1 nm (10^–9 m) to 100 nm (10^–7 m).

20. B

Explanation: The solution of substance A' in water is colloidal solution. The colloidal particles scattered the light when it was passed through the solution due to Tyndall effect.