Chhattisgarh State Class 7 Science Chapter 3 Solution

CG SCERT Chhattisgarh State Board Class 7 Science (Science and Technology) Chapter 3 Structure of matter Exercises Questions and Answers.

(1) Match the names of the elements with the corresponding symbols –

(i) Carbon

(d) (a) Cl
(ii) Sulphur (t)

(b) Mn

(iii) Chlorine

(a) (c) Na
(iv) Magnesium (e)

(d) C

(v) Zinc

(i) (e) Mg
(vi) Manganese (b)

(f) S

(vii) Sodium

(c) (g) K
(viii) Gold (j)

(h) Fe

(ix) Iron

(h) (i) Zn
(x) Potassium (g)

(j) Au

(2) Match the names of elements with their atomicity –

(i) Iodine

(d) (a) 8
(ii) Sulphur (a)

(b) 4

(iii) Phosphorus

(b) (c) 1
(iv) Sodium (c)

(d) 2

(3) Fill in the blanks –

(1) —— Metals is found in a liquid state at normal temperature.

Answer:- Mercury.

(2) Element are formed by the some type of ——

Answer:- Atom.

(3) Air is a ——-.

Answer:- Mixture.

(4) ——- Sate of matter can be easily compressed.

Answer:- Gas.

(4) Balance the following chemical equations –

(I) Mg + O2 -> MgO

Answer:- 2Mg + O2 -> 2MgO2

(II) N2 + H2 -> NH3

Answer:- N2 + 3H2 -> 2NH3

(III) SO3 -> + O2

Answer:- 2SO3 -> 2SO2 + O2

(5) Write chemical for the following reactions –

(1) An atom of sulphur react with a molecule of oxygen to form a molecule of sulphur dioxide.

Answer:- S + O2 -> SO2

(2) An atom of zinc combine with two molecules with two molecules of hydrochloric acid to form a molecule of zinc chloride & a molecules of hydrogen.

Answer:- ZN + 2HCL -> ZNCL2 + H2

Define the following –

(a) Element – Element are the pure substance which have only one constituents. Ex – gold, Iron, Silver, Oxygen etc.

(b) Component – compound are pure substance that are formed by when two or more elements combine together in a fix ratio Ex- H2O, SO2, NH3 etc.

(7) Give three example of each of an element & a compound:-

Answer:- Example of elements – Silver, gold, copper, Aluminium, Iron

Example of compound – Water, Ammonium carbon dioxide, SO2

(8) When substance A is hated then two substance are formed. Explain with reason if the substance A is element or compound.

Answer:- Substance A is compound. A heat X+Y

  • Substance A is not element because we cant separate constituent of element.
  • We can separate constituent of compound by heating (chemical process)

(9) Explain the difference between –

(1) Mixture & compound

(2) Element & compound



(1) Mixture are formed when two or more substance combine in any ratio.

(1) Compound are pure substance that are form when two or more element combine (Fix ratio)
(2) Constituent of a mixture are not in fix ratio

(2) Constituent of a compound are in fix ratio.

(3) Mixture can be separated by simple physical process

(3) Compound can’t be separated by simple physical process
(4) The properties of a constituent in mixture remain same (4) The properties of a constituent in a compound changes
(5) Example – smoke, lemone juice

(5) Example – Water, Ammonia




(1) Pure substance are those which have only one constituent know as element

(1) Two or more element can react (chemical reaction) with each other to form compound
(2) An element has same type of atom

(2) Compound has difference type of atom

(3) Constituent can’t be separated from an element

(3) Constituents can be separate from compound
(4) Example – oxygen, Nitrogen

(4) Example – salt, sugar, Water

Updated: January 10, 2021 — 1:17 am

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