NCERT Solutions For Class 10 Science Free PDF Download (Updated For )

Question 1: What is meant by a skeletal chemical equation? Ansaer suitable chemical reaction, differentiate between a skeletal chemical equation and a balanced chemical equation. Answer 1: If the number of atoms of any element in a chemical equation is not equal on both sides, then it is a skeletal equation. For example:. Here, the number of chlorine and hydrogen atoms are not equal questoon both sides. In a 10th science ncert question answer question equation, the numbers of atoms of different elements on both sides of a chemical equation are equal.

Question 2: Questioon the following terms with 10th Science Ncert Question Answer Question examples in each case: i Oxidation and ii Reduction. Answer 2: 10th science ncert question answer question Oxidation: it us a process a in which oxygen or 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question any electronegative element is added up or b hydrogen or any electropositive element is removed.

Examples are: a Sulphur burns in the air with a blue flame to Answer Science Question 10th Ncert Question form sulphur dioxide. Here oxygen is added up to sulphur.

Question 3: Nxert is respiration considered an exothermic reaction? Answer 3: During digestion, food is qiestion down into Question Science Ncert 10th Answer Question simpler substances. Food like rice, potato and bread are made up of carbohydrates. These carbohydrates are further broken down into glucose. Glucose during respiration inhalation of oxygen is oxidised with the liberation of energy as shown. Thus, respiration is an exothermic process.

Examples are: a Hydrogen reacts with chlorine to form hydrogen chloride. Important Questions on 10th Science Ncert Question Answer Question 10th Science Chapter 1 What is a balanced chemical equation? Why should chemical equations be balanced?

A reaction which 10th science ncert question answer question an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation. The law of conservation of mass states that 10th Science Ncert Question Answer Question mass can neither be created nor destroyed. Hence, in queztion chemical reaction, the total mass of reactants should be equal to the total mass of the products.

It means that the total number of atoms of each element should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question equations should be balanced. Why is respiration considered an exothermic reaction? Energy in our body is obtained from the food 10th science ncert question answer question eat.

During digestion, large molecules of food are broken down into simpler substances such as glucose. Glucose combines with oxygen in the cells and provides energy. The special name 10th Science Ncert Question Answer Question of this combustion reaction is respiration. Since energy is released in the whole process, it is an exothermic process. Why are decomposition reactions called the opposite of combination reactions? Decomposition reactions are those in which a compound breaks down into two or more substances.

These reactions require a source of energy to proceed. Thus, they are 10th Science Ncert Question Answer Question the exact opposite of combination reactions in which two 10th science ncert question answer question more substances combine to give a new substance with the release of energy.10th Science Ncert Question Answer Question

Why do we apply paint on iron articles? Iron articles are painted because applying paints prevents them from rusting. When painted, the contact of iron articles from moisture and air is cut off. Hence, rusting is prevented their presence is essential for rusting to take place. Oil and fat containing food items are flushed with 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question nitrogen. Nitrogen is an inert gas at room temperature and does not easily react with oil and fat containing items.

On the other hand, oxygen reacts with food 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question substances and makes them rancid. Thus, bags used in packing food items are flushed with nitrogen gas to remove oxygen inside the pack. When oxygen is not present 10th Science Ncert Question Answer Question inside the pack, rancidity of oil and fat containing food items is avoided. Chapter 2: Acids, Bases and Salts �.

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Some major topics covered in this chapter are:. Control and Coordination chapter gives details of different ways in which organisms respond to the stimuli. Here you also get to know about the human nervous system, automatics and voluntary actions, exocrine and endocrine glands, etc. How do Organisms Reproduce chapter students get to learn different methods of reproduction in plants and animals and get aware of the various methods of birth control in humans.

Some of the important topics discussed in this chapter are:. Heredity And Evolution chapter deals with the details related to heredity and evolution of different species.

Go through the major topics mentioned below:. Light Reflection and Refraction explains the concepts of reflection and refraction of light. Some important topics to learn from this chapter 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question are:.

The Human Eye and Colorful World chapter students get to know each and every detail of the human eye from its structure to its working. Various defects of vision are also discussed here.

It also explains atmospheric refraction and various phenomena related to it. Some major topics discussed in this chapter are:.

Electricity chapter 10th Science Ncert Question Answer Question explains electric current, its applications and various effects related to it. Lithium, sodium, potassium are metals that react with water to liberate hydrogen. Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common Solution: a. These elements are alkali metals and they have 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 1 valence electron in their outermost shell and are therefore very unstable and reactive.

These elements each have full outermost subshell, which results in high stability. They only 10th Science Ncert Question Answer Question react with other elements in extreme circumstances, the trait for which they are named.

Question 12 In the Modern periodic table, which are the metals among the first ten elements? Solution: The metals are Lithium and Beryllium. Question 13 By considering their position in the periodic table, which one of the following elements would you expect to have maximum metallic characteristic?

Question 14 Which of the following statements is not a correct statement about the trends when going from left to right across the periods of the periodic table? Question 15 Element X forms a chloride with the formula XCl 2 , which is a solid with a high melting point. X 10th Science Ncert Question Answer Question Answer Science Ncert Question 10th Question would most likely be in the same group of the periodic table as a.

Si Solution: b. Question 16 Which element has? Two shells, both of which are completely filled with electrons? The electronic configuration of 2,8,2? A total of three shells, with four electrons in its valence shell? A total of two shells, with three electrons in its valence shell?

Twice as many electrons in its second shell, as in its first shell? Neon 2,8 b. Magnesium 2,8,10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 2 c. Silicon 2,8,4 d. Boron 2,3 e. Carbon 2,4. Question 17 What property do all elements in the same column of the periodic table as fluorine have in common? Solution: These elements all have 7 electrons in their outermost shells and these often exist as salts, combined with elements from the 10th Answer Ncert Science Question Question Alkali metal group.

Question 18 An atom has electronic configuration 2,8,7. What is the atomic number of this element? Question 19 Which type of ion, 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question cation or anion, will be formed by element A? Anion will be formed by element A. Question 20 Nitrogen atomic number 7 and phosphorus atomic number 15 belong Question 10th Ncert Question Science Answer to group 15 of the periodic Table. Solution: Electronic configuration � Nitrogen � 2s 2 2p 3 and Phosphorus � 1s 2 2s 2 2p 6 3s 2 3p 3.

Nitrogen will be more electronegative; this is because its atom has small size due to which Online Question Answer Mathematics 8th Edition Pdf the attraction of its nucleus for the incoming electron is 10th Science Ncert Question Answer Question more. Question 21 How does the electronic configuration of an atom relate to its position in the Modern periodic table? Solution: The electronic configuration of an atom increases Question Ncert 10th Question Answer Science in the outermost valence shell which relates to its position in the Modern periodic table.

Question 22 In the Modern periodic table, calcium atomic number 20 is 10th Science Ncert Question Answer Question surrounded by elements with atomic numbers 12, 19, 21 and Solution: The atomic number of calcium is 20, so its electronic configuration is 2, 8, 8, 2.

Thus, 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question calcium has 2 valence electrons in its outermost shell. Now, the element which has 2 valence electrons, will have physical and chemical properties resembling to that of calcium.10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question

The electronic configuration of element having atomic number 12 is 2, 8, 2. It has 2 valence electrons just like calcium. So, the element having atomic number 12 10th Science Ncert Question Answer Question will have physical and chemical properties resembling that of calcium. Question 23 Where do you think should hydrogen be placed in the Modern periodic table? Solution: Hydrogen element has been placed at the top of group 1, above the alkali metals because the electronic configuration of hydrogen is similar to those of alkali metals.

Question 10th Science Ncert Question Answer Question 1. Which of the following is the outermost shell for elements of 2nd period? Because in period 2, there are two shell, K and L. Question 2. An element which is an essential constituent of all organic compounds belongs to [NCERT Exemplar] a group 1 b group 14 c group 15 d group 16 Answer: b 10th Science Ncert Question Answer Question Constituent of all organic compounds is carbon.

It belongs to group Question 3. Which one of the following elements exhibit maximum number of valence electrons? Therefore, P has 10th Science Ncert Question Answer Question maximum number of valence electrons, i. Question 4. Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 30 respectively belong to the same period?

Since, 2nd period has elements having atomic number 3 to Question 5. Which pair of elements belong to the same group? Elements 10th Science Ncert Question Answer Question which differ in atomic number by 8, i. Question 6. Which one of the following elements found a place in the periodic table later?

Question 7. Which 10th Science Ncert Question Answer Question of the following are the characteristics of isotopes of an element? Question 8. Which of the following elements would lose an electron easily? But out of K and 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question Na, K will lose electron more easily because the force of, attraction on valence electron of K is least among the given elements. Question 9. Which among 10th Science Ncert Question Answer Question the following elements has the largest atomic radii?

Na and K are in the same group and K is below Na, so K will have higher atomic radius, 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question i. In a period on moving left to right, atomic radius decreases. Since, K and Ca are in the same period and K is in 1st group and Ca is in 2nd group, so atomic radius of K will be more than Ca, i. Also Na and Mg are in the same period, but Na belongs to 1st group and Mg belongs to 2nd group, so atomic radius of Na is more than Mg, i.

Hence, we can say that the atomic radius of K is largest. Question Which of the following statements is not a correct statement about the trends when going from left to right across the periods of 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question periodic table? With the increase of nudear charge, the force binding the electron increases so the atom lose the electrons with more difficulty, not easily.

Which one of 10th Science Ncert Question Answer Question the following depicts the correct representation of atomic radius r of an atom? Hence ii and iii are the correct representations. Which of the following statement s about 10th Science Ncert Question Answer Question the modern periodic table are incorrect?

All the elements in the modern periodic table are arranged on the basis of their increasing atomic number.

All the isotopes can 10th Science Ncert Question Answer Question be placed at one place in the same group of the periodic table. The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. Question 10 Why do stars twinkle?

Answer: Stars appear to twinkle due to atmospheric refraction. Stars are far away. So, they are the point source of 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question light. As the path of light coming from stars keep changing, thus the apparent position of stars keep changing and amount of light from stars entering the eye 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question keeps twinkling.

Due to which a star sometimes appear bright and sometimes dim, which is the effect of twinkling. Question 11 Explain why the planets do not twinkle? Answer: 10th Science Ncert Question Answer Question The planets are much nearer to the earth than stars and because of this they can be considered as large source of light.

If a planet is 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question considered to be a collection of a very large number of point sources of light, then the average value of change in the amount of light entering 10th Science Ncert Question Answer Question the eye from all point size light sources is zero. Due to this the effect of twinkling is nullified. Question 12 Why does the sun appear reddish early 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question in the morning? Most of the part of blue light and light of small wavelength gets scattered by dust particles near the horizon.

So, the light reaching our 10th Science Ncert Question Answer Question eyes is of large wavelength. Due to this the sun appears reddish at the time of sunrise and sunset. Question 13 Why does the sky appear dark instead of blue to an astronaut? Answer: As an astronaut moves away from the atmosphere of earth, the atmosphere becomes thin. Due to the absence of molecules or 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question dust particles in air, the scattering of light does not take place.

Thus, sky appears dark in the absence of scattering. Functioning of a lens in human eye, 10th Science Ncert Question Answer Question defects of vision and their corrections, applications of spherical mirrors and lenses. Refraction of light through a prism, dispersion of light, scattering of light, applications in daily life.10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question Question Question Answer 10th Ncert Science 10th Science Ncert Question Answer Question

Formulae Handbook for Class 10 Maths and Science. Question 1. What is meant by power of accommodation of the eye? Answer: The power Of accommodation of the eye is the ability of the eye to observe the distinct objects clearly which are situated at a large distance from the eye. The ciliary muscles are responsible to 10th Science Ncert Question Answer Question change the focal length Of the eye lens. The value of power of accommodation Of human eye is about 4D.

Question 2. A person with a myopic 10th Science Ncert Question Answer Question eye cannot see objects beyond 1. Answer: The far point for myopic eye is 1.

Question 3. What is the far point and near point of the human eye with normal vision? Answer: For human eye with normal vision, far point is at infinity and near point is at 25 cm from the eye.

Question 4. A 10th Science Ncert Question Answer Questio10th Science Ncert Question Answer Question n student has difficulty reading the blackboard while sitting in the last row. Answer: As the child has difficulty in reading the blackboard, he is suffering from myopia or short sightedness. To correct this defect, he has to use spectacles with concave lens of suitable focal length. Page � Question 1. The human eye can 10th Science Ncert Question Answer Question focus objects at different distances by adjusting the focal length of the eye lens. This is due to a presbyopia b accommodation c near-sightedness d far-sightedness Answer: b Human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye.

This is possible due to the power of accommodation of the eye lens. The human eye forms the image of an object at its a cornea b iris c pupil d retina Answer: d 10th Science Ncert Question Answer Question 10th Science Ncert Question Answer Question The human eye forms the image of an object at its retina.

The least distance of distinct vision for a young adult with normal vision is about a 25 m b 2. It is 25 cm for a young adult with normal visions. The change in focal length of an eye lens is caused by 10th Science Ncert Question Answer Question the action of the a pupil b retina c ciliary muscles d iris Answer: c The relaxation or contraction of ciliary muscles changes the curvature of the eye lens.

The change in curvature of the eye lens changes the focal length of the eyes. Hence, the change in focal length of an eye lens is caused by the action of ciliary muscles.

Question 5. A person needs a lens of power � 5. Question 6. The far point of a myopic person is 80 cm in front of the eye. Question 7. Make a diagram to show how hypermetropia is corrected. Assume that near point of the normal eye is 25 cm. Question

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