Elements and Compounds Class-7th Goyal Brothers Chemistry Solutions Ch-3 Unit-1

Elements and Compounds Class-7th Goyal Brothers Chemistry Solutions Ch-3 Unit-1 We Provide Step by Step Answers of Objective, True False , Fill in the blanks, Match the following , Study Questions of Chapter-3(Elements, compounds and mixture),Unit-1 (Elements and compounds). Visit official Website  CISCE  for detail information about ICSE Board Class-7.

Elements and Compounds Class-7th Goyal Brothers

Chemistry Solutions Chapter-3 Unit-1

Board ICSE
Class 7th
Subject Chemistry
Book Name Goyal Brothers
Theme-3 Elements, Compounds and Mixture
Unit-1 Element and Compound
Topic Solution of exercise questions
Session 2023-24

Note – In this article you can get answer of these questions such as difference between elements and compound with example. What is element / compound, properties of elements and compound

OBJECTIVE TYPE QUESTIONS

Chemistry Solutions Chapter-3 Unit-1

A. Fill in the blanks :

  1. The symbol ‘Au’ for an element stands for _gold_.
  2. The molecules of chlorine gas is _diatomic_.
  3. The smallest unit of matter which can exist independently and can retain all its physical and chemical properties is called _molecules_.
  4. The process of breaking down of a chemical compound into elements is called _analysis_.
  5. The symbol ‘H2O’ for a compound stands for _steam_.

B. Statement given below are incorrect. write the correct correct statement:

1. The smallest unit of a pure substance is called an atom.

Correct Statement: The smallest unit of a pure substance is called molecules.

2. The symbol of the element sodium is ‘So’.

Correct Statement: The symbol of the element sodium is ‘Na’.

3. The symbol NaHCO3 stands for washing soda.

Correct Statement: The symbol Na2CO3 stands for washing soda.

4. The symbolic representation of a molecule of a compound is called symbol of that compound.

Correct Statement: The symbolic representation of a molecule of a compound is called Chemical formula.

5. The number of atoms in a molecules of sulphur are 4.

Correct Statement: The number of atoms in a molecules of sulphur are 8.

C. Match the statement in Column A with those in Column B:

Column A

Column B

1. The symbolic representation of a molecule of a chemical compound.

(a) Atom

2. The symbolic representation of a molecule of ozone.

(b) CuS

3. The symbolic representation of a molecule of nitric acid.

(c) O3

4. The symbolic representation of a molecule of copper sulphide.

(d) HNO3

5. The smallest particle of an element which may or may not exist independently, but always takes part in a chemical reaction.

(e) Formula

Answer:

Column A

Column B

1. The symbolic representation of a molecule of a chemical compound.

(e) Formula

2. The symbolic representation of a molecule of ozone.

(c) O3

3. The symbolic representation of a molecule of nitric acid.

(d) HNO3

4. The symbolic representation of a molecule of copper sulphide.

(b) CuS

5. The smallest particle of an element which may or may not exist independently, but always takes part in a chemical reaction.

(a) Atom

D. Write ‘True’ or ‘False’ for the following statements :

  1. 80 metals have been discovered so far. [F]
  2. Bromine is the only liquid non-metal. [T]
  3. The molecular formula of chlorine is Cl4. [F]
  4. Plants make their food by the process of analysis. [F]
  5. The smallest unit of a substance is called its atom. [T]

E. Tick (√) the most appropriate answer.

1. The symbol for the sodium metal is:

(a) So

(b) Si

(c) Na

(d) Sm

Ans: (c) Na

2. The liquid metal at room temperature is :

(a) Sodium

(b) Mercury

(c) magnesium

(d) Calcium

Ans: (b) Mercury

3. The formula for one molecule of phosphorous is :

(a) P

(b) P2

(c) P4

(d) P8

Ans: (c) P4

4. The process of breaking down of a compound into elements is called :

(a) Synthesis

(b) Symbiosis

(c) Analysis

(d) Decombination

Ans: (c) Analysis

5. The symbolic representation of the molecule of a chemical compound is :

(a) formula

(b) symbol

(c) reactant

(d) product

Ans: (a) formula

STUDY QUESTIONS

Chemistry Solutions Chapter-3 Unit-1

Question 1. 

(a) Define an element.

Answer: An element is a pure substance that cannot be broken down by any physical or chemical means into simpler substances.

(b) How many elements have been discovered so far? How many of the discovered elements are metals?

Answer: The discovery of the 118 chemical elements known to exist so far. Among the discovered elements there are 92 metals at present.

Question 2. What are (a) normal elements (b) harmful elements? Give two examples of each.

Answer: The elements of groups 1, 2 and 13 to 17 are called normal elements. These elements have their outermost shell incomplete and are highly reactive. Example: Fluorine (F), Chlorine (Cl) etc.

The elements that give out harmful radiations are called Radioactive Elements. Example: Uranium (U), Potassium (K), etc

Question 3. 

(a) Define the term metal.

Answer: Metals are materials that are hard, lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Examples of metals are iron, copper, aluminium, calcium, magnesium, etc.

(b) Give the names of 6 common metals along with their symbols.

Answer: The names of 6 common metals along with their symbols are :-

  • Sodium: The symbol for sodium is ‘Na’.
  • Magnesium: The symbol for magnesium is ‘Mg’.
  • Iron: The symbol for iron is ‘Fe’.
  • Copper: The symbol for copper is ‘Cu’.
  • Silver: The symbol for silver is ‘Ag’.
  • Gold: The symbol for gold is ‘Au’.

Question 4. (a)Define the term non-metal.

Answer: A non metal is a material which do not have properties of metals like lustre. They are non malleable, non ductile, non sonorous and bad conductor of heat and electricity. Example- Carbon, Sulphur,

(b) Give the names and symbols of:

(i) Three non-metals which are solids.

Answer: Name of the three non-metals which are solid = Carbon(Symbol C), Sulphur(Symbol S), Phosphorus(Symbol P), Iodine(Symbol I).

(ii)Three non-metals which are gases.

Answer: Name of the three non-metals which are Gases = Hydrogen (Symbol H), Nitrogen (Symbol N), Oxygen (Symbol O)

(iii) One non-metal which is a liquid.

Answer: Name of a mom-metal which is a liquid = Bromine (Symbol Br)

Question 5. (a)What are noble gases ?

Answer: Noble gases are sometimes called inert gases, and they are the elements in Group 18 of the periodic table. They comprise the elements helium, neon, argon, krypton, xenon, and radioactive radon, which has no known stable isotopes.

(b) Give the names and symbols of four noble gases?

Answer: The names and symbols of four noble gases are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr).

Question 6. (a)Define: (i) an element (ii) a molecule

Answer: (a) An element is a pure substance that cannot be broken down by any physical or chemical means into simpler substances.

(b) The smallest particle of a substance that has all of the physical and chemical properties of that substance

(b) Give three examples of each molecules which has:

(i) similar kind of atoms

Answer: Three examples of each molecule which has similar kind of atoms :-

  • Hydrogen.
  • Oxygen.
  • Nitrogen.

(ii) Different kind of atoms

Answer:  Three examples of each molecule which has different kind of atoms are :-

  • Carbon Dioxide
  • Water
  • Sodium Chloride

Question 7. What do you understand by the term compound?

Answer: A compound is a substance that results from a combination of two or more different chemical elements, in such a way that the atoms of the different elements are held together by chemical bonds that are difficult to break.

Question 8. What do the following formulae represent?

(a) 2O= It represents two molecules of Oxygen.

(b) H2= It represents two atoms of hydrogen element.

(c) 10 H2O= It represents ten molecules of water.

(d) 4 Cl = It represents four molecules of chlorine.

(e) 5CO2 = It represents 5 molecules of Carbon dioxide.

(f) FeS = It represents one molecule of iron sulphide.

Question 9. Write the number of atoms of each element in the molecules of following compounds:

(a) K2CO3=  There are 2 atoms of potassium, 1 atom of carbon and 3 atoms of oxygen are present.

(c) Pb(NO3)2 = There are 1 atom of lead (Pb), 2 atoms of nitrogen and 6 atoms of oxygen.

(d) CuSO4= There are 1 atom of copper, 1 atom of sulphur and 4 atoms of oxygen.

(e) NaHCO3 = There are 1 atoms of sodium, 1 atom of hydrogen, 1 atom of carbon and 3 atoms of oxygen.

(f) CH4= There are 1 atom of carbon and 4 atoms of hydrogen.

Question 10. Write the chemical names of the following compounds:

(a) H2SO4 = Sulphuric Acid

(b) NaOH = Sodium hydroxide

(c) Na2CO3 = Sodium Carbonate

(d) CuSO4 = Copper Sulphate

(e) NaHCO3 = Sodium Bicarbonate

(f) CH4 = Methane

Question 11. Write chemical formulae for each of the following compounds.

(a) Hydrochloric acid = HCl

(b) Ferrous sulphate = FeSo4

(c) Zinc sulphate= ZnSo4

(d) Calcium oxide = CaO

(e) Silver nitrate = AgNO3

(f) Copper oxide = CuO

— : end of Elements and Compounds Class-7th Goyal Brothers Chemistry Solutions Ch-3 Unit-1 :–-

Return to –  ICSE Class -7 Goyal Brothers Chemistry Solutions

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