CBSE Class 9 Science Atoms and Molecules assignment

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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

Questions

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

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