# Atoms and Molecules Worksheet

Given below are the Class 9 Science CBSE worksheet for Atoms and Molecules
(a) Short questions
(b) True and False problems
(c) Fill in the blank's
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## Fill In The Blanks

1. During a chemical reaction, the sum of the _________ of the reactants and products remain unchanged.
2. In a pure chemical compound, elements are always present in a ________ proportion by mass.
3. Clusters of atoms that act as an ion are called __________ ions.
4. In ionic compounds, the charge on each ion is used to determine the ________of tye compound.
5. The Avogadro constant _________ is defined as the umber of atoms in exactly ________ of crbon-12
6. Mass of 1 mole of a substance is called its __________.
7. The abbreviation used for length names of elements are termed as their _______.
8. A chemical formula is also known as a ________.
9. Those ions which are formed from single atoms are called _________.
10. Ionic compounds are formed by the combination between ________ an ______.
11. The valency of an ion is _________ to the charge on the ion.
12. Mole is a link between the __________ and __________.
13. The SI unit of amount of a substance is __________.

## True / False

1. Formula mass of $Na_2O$ is 62 amu.
2. Those particles which have more or less electrons than the normal atoms are called ions.
3. Formula for sulphur dioxide is $SO_3$.
4. Molar mass of ethyne ($C_2H_2$) is 26 g/mol.
5. 22 gm of $CO_2$ consists of 1 mole.
6. Number of molecules in 32 gram of oxygen is $6.02 \times 10^{23}$.
7. Water is an atom.
8. Formula for sulphur dioxide is $SO_2$.
9. Clusters of atoms that act as an ion is called polyatomic ion.
10. Mass of 1 mole of a substance is called its formula mass.
11. In a pure chemical compound, elements are always present in a definite proportion by mass.

1. Define term mole.

3.What is gram atomic weight?

4. What is the difference between $CO_2$ and $2CO_2$?

5. Name the following compounds $PC_3$ and $SO_2$.

6. In the smallest whole-number ratio must N and O atoms combine to make dinitrogen to tetroxide $N_2O_4$? What is the mole ratio of the elements in this compound?

7.How many moles of sodium atoms correspond to $1.56 \times 10^{21}$ atoms of sodium?

8. What is the relationship between the formula weight of a substance and its molar mass?

9. How many grams of silver are in 0.263 mol of g?

10.How many atoms are $1.00 \times 10^{-9}$ g of lead?

11.How many grams of iron are needed to combine with 25.6g of O to make $Fe_2O_3$?

12.What is the mass of 4 moles of aluminium atoms? ( Atomic mass of AI = 27u)

13.Calculate the mass of $6.022 \times 10^{22}$ atoms of He.

14.Calculate the number of moles in $3.011 \times 10^{22}$ molecules of carbon dioxide.

15.A sample of 45.8g of $H_2SO_4$ contains how many moles of $H_2SO_4$?

16.What s the mass in grams of 5 moles of Fe?

17.How many moles of NaCI are present in 20 gm of the substance?

18.How many grams of O is present in 50 gm of $CaCO_3$?

19.How many grams of $CO_2$ are present in 0.1 mole $CO_2$?

20.Describe the difference between the mass of a mole of oxygen atoms (O) and the mass of a mole of oxygen molecules ($O_2$).

21.What do you understand by the term Formula unit?

Reference Books for class 9 science

Given below are the links of some of the reference books for class 9 science.

These books by S.Chand Publications are detailed in their content and are must have books for class 9 students. Some other books that might be worth considering are
1. Oswaal CBSE Question Bank Class 9 Science Chapterwise & Topicwise We all know importance of practicing what we have studied. This book is perfect for practicing what you have learned and studied in the subject.
2. Pearson Foundation Series (IIT-JEE/NEET) Physics, Chemistry, Maths & Biology for Class 9 (Main Books) | PCMB Combo These Foundation books would be helpful for students who want to prepare for JEE/NEET exams. Only buy them if you are up for some challenge and have time to study extra topics. These might be tough for you and you might need extra help in studying these books.
3. Foundation Science Physics for Class - 9 by H.C. Verma This is one of my favorite Physics book for class 9. Most of the book is within the limits of CBSE syllabus. It might overwhelm you with its language but I feel if you can understand the content is authentic with plenty of problems to solve.

You can use above books for extra knowledge and practicing different questions.

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