Class 10 Science - Chapter Metals and Non-Metals NCERT Solutions | Samples of four metals A, B, C and D wer

Give an example of a metal which

  (i) is a liquid at room temperature.
  (ii) can be easily cut with a knife.
  (iii) is the best conductor of heat.
  (iv) is a poor conductor of heat.

Write equations for the reactions of

   (i) iron with steam
   (ii) calcium and potassium with water.

(i) Write the electron-dot structures for sodium, oxygen and magnesium.

(ii) Show the formation of Na₂O and MgO by the transfer of electrons.

(iii) What are the ions present in these compounds?

You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Food cans are coated with tin and not with zinc because

(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.

Why do ionic compounds have high melting points?

Metallic oxides of zinc, magnesium and copper were heated with the following metals.

In which cases will you find displacement reactions taking place?

Why is sodium kept immersed in kerosene oil?

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Give reasons

(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.

What is a good source of energy?

Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?

What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

What changes can you make in your habits to become more environment-friendly?

What is the difference between a reflex action and walking?

What is the importance of DNA copying in reproduction?

If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Why should a magnesium ribbon be cleared before burning in air?

Define the principal focus of a concave mirror.

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?

The magnification produced by a plane mirror is +1. What does this mean?

The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

  (a) NaCl          (b) HCl          (c) LiCl          (d) KCl

Describe the structure and functioning of nephrons.

Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?

How would these advantages differ from the advantages of using a long-term perspective in managing our resources?

How are the areas of study – evolution and classification – interlinked?