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
|
Mixture |
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 |
|
Element |
Compound |
|
(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 |
