CBSE Class 9 Science Atoms and Molecules assignment

Read and download free pdf of CBSE Class 9 Science Atoms and Molecules assignment. Get printable school Assignments for Class 9 Science. Standard 9 students should practise questions and answers given here for Science in Grade 9 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 9 Science prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations

Atoms And Molecules Class 9 Science Assignment Pdf

Class 9 Science students should refer to the following printable assignment in Pdf for Atoms And Molecules in standard 9. This test paper with questions and answers for Grade 9 Science will be very useful for exams and help you to score good marks

Class 9 Science Assignment for Atoms And Molecules

Atoms and Molecules

Q 1 144 grams of pure water is decomposed by passing electricity. 16 grams of hydrogen and 128 grams of oxygen are obtained.
Which chemical law is illustrated by this statement?

Q 2 What do you mean by Molar Mass ?

Q 3 What is atomic mass unit ?

Q 4 What are molecules?

Q 5 What name is given to the number 6.023 x 1023?

Q 6 Name the building blocks of matter.

Q 7 How many metres are there in 1 nanometer (nm)?

Q 8 Define atomicity.

Q 9 Write the chemical formula of glucose.

Q 10 Which subatomic particle was not present in Thomson‘s model of the atom?

Q 11 Write the symbol of element lead and iron.

Q 12 Write down the formulae of aluminium sulphate and ethanol.

Q 13 What is the atomicity of –
(a) Ozone (b) Nitrogen
(c) Neon (d) Sulphur


Q 1 State main points of Dalton atomic theory.

Q 2 State the law of constant proportion. 

Q 3 state the law of conservation of mass

Q 4 If 90g of pure water is obtained through 80g of oxygen and Xg of hydrogen. a. Find the value of X. b. Which chemical law is illustrated by this statement?

Q 5 Calculate the molecular mass of the following: a. H2O b. HCl c. H2S

Q 6 If 6g of hydrogen combine with 48g of oxygen, how many grams of water is obtained?

Q 7 If carbon and oxygen combine in a definite ratio of 3:8 to form carbon dioxide. What mass of oxygen gas is required in carbon dioxide with 10 g of carbon?

Q 8 Give symbol of the followinga. oxygen b. hydrogen c. carbon

Q 9 If atomic mass of carbon is 1u then what is the atomic mass of nitrogen (N=14, C=12)?

Q 10 Identify the anions, cations and charge present on them in following molecules: HCl , NaCl , H2O , Al2O3

Q 11 Write the chemical formula of the following:

a. Oxygen

b. Carbon dioxide

c. Ammonia

d. Calcium carbonate

 Exam Questions NCERT Class 9 Science Chapter 3 Atoms And Molecules


Question. Define law of conservation of mass.
Ans : Law of conservation of mass states that, ‘Mass is neither created nor destroyed in a chemical reaction.’


Question. Name the scientists whose experimentation established laws of chemical combination. Name the laws also.
Ans : Antoine Laurent Lavoisier and Joseph L. Proust experimented and established two laws of chemical combination. These laws are : (i) Law of conservation of mass, (ii) Law of constant proportions.


Question. Give one example each of (i) Monovalent cation, (ii) Bivalent cation, (iii) Monovalent anion, (iv) Bivalent anion.
Ans : (i) K+ or Na+
         (ii) Mg+2 or Ca+2
         (iii) F– or Cl–
         (iv) O2– or S2–


Question. How can Dalton’s atomic theory explain the Law of Constant Proportions?
Ans : According to Dalton’s atomic theory, atoms of the same elements are same. Also atoms combine in whole number. This means that the atoms can combine with each other in a simple fixed ratio to form molecules.


Question. What is ion?
Ans : An ion is a charged particle. It can be positive or negative.

Question. What do you mean by symbols of elements?
Ans : Each element is represented by a letter or group of two letters to write the chemical reactions conveniently. It is called symbol.


Question. How did the scientist lay the foundation of chemical sciences? Name the scientist.
Ans : Antoine Laurent Lavoisier laid the foundation of chemical science by establishing two important laws of chemical combination.


Question. An element has 8 electrons in its valence shell. What is its general name?
Ans : Noble gas.

Question. Write the names of the following compounds :
(a) NiS
(b) Mg(NO3)2
(c) Na2SO4
(d) Al(NO3)3
(e) K3PO4 (f) Ca3N2

Ans : (a) Nickel sulphide,
         (b) Magnesium nitrate,
         (c) Sodium sulphate,
         (d) Aluminium nitrate,
         (e) Potassium phosphate,
         (f) Calcium nitride.

Question Give the derivation source of symbol of sodium (Na).
Ans : The symbol of ‘Na’ for sodium is derived from its Latin name ‘Natrium’.

Question. Give the full form of amu?
Ans : The full from of amu is atomic mass unit.

Question. Write the symbols of tungsten and iron.
Ans : (i) Tungsten (W) and
         (ii) Iron (Fe)

Question. All elements have charged valency. Explain.
Ans : No, all elements do not form ions thus they, do not have a charge. For example : Carbon has a valency of 4 and nitrogen has a valency of 3. Non-metals are formed without a charged valency. Example : In carbon tetrachloride, carbon has valency of 4 and chlorine has a valency of 1.

Question. What are molecules? Give brief explanation of the arrangement of the constituent atoms in the molecules.
Ans : A molecule is the smallest particle of an element or compound which is stable in normal conditions. And it can freely show all the properties of that element or compound. It may be made up of one, two or more atoms. Molecule with one atom called monoatomic. E.g. helium, neon, etc. Molecule with two atoms called diatomic. E.g.
Cl2, O2. Similarly, there are molecules containing three atoms (CO2), four atoms (P4) and so on.

Please refer to attached file forCBSE Class 9 Atoms and Molecules assignment



Click to View or Download pdf file
Click for more Science Study Material

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

CBSE Class 10 Revised Syllabus

Last year CBSE had to reduce the syllabus because of the pandemic situation but it was not very effective because there were no examinations. This year to avoid any confusion and conflict, CBSE has decided to reduce the syllabus into term 1 and term 2. 50 percent of...

Score well in Class 12 English Boards Exam

12th Board exams are an important part of students' lives. The marks obtained in the board exam decide the college in which one can study. In class 12 the syllabus of each and every subject increases vastly and it is difficult to cover up every point. In English also...

How To Solve Unseen Passages In English

Unseen passages may contain one or many paragraphs. This is one of the important yet easy parts for a student to get marks. Students should thoroughly study and understand the passage to answer the related questions. The unseen passages are there just to test the...

MCQ Question based CBSE examination

For 2021-22 CBSE has launched MCQ question-based examination for Term 1 & Term 2 board examinations. The entire syllabus has been divided into two parts each including 50% of the entire syllabus. To score well, students must practice as per the new CBSE term-wise...

Studies Today