Activity 3.2 Class 9 Science Atoms and Molecules
Activity 3.2
Class 9 Science belongs to Chapter 3 Atoms and Molecules Class 9 Science. You will
get a complete solution with an explanation and a conclusion. After reading activity 3.2, you will be able to answer the questions based on the activity.
Activity 3.2
Class 9 Science Atoms and Molecules
You are suggested to study NCERT activity 3.2 class 9 science Atoms and Molecules
explanation with a conclusion so that you can attempt questions based on the
activity 3.2 class 9 science. Activity 3.2 class 10 science will be very useful
for you.
Activity 3.2 Class 9 Science
· Refer to table 3.4 for the ratio by
mass of atoms present in molecules and table 3.2 for atomic masses of elements.
Find the ratio by the number of atoms of elements in the molecules of compounds
given in Table.
|
Compound |
Combining elements |
Ratio by Mass |
|
Water |
Hydrogen, oxygen |
1:8 |
|
Ammonia |
Nitrogen, Hydrogen |
14:3 |
|
Carbon dioxide |
Carbon, Oxygen |
3:8 |
· The ratio by number of atoms for
a water molecule can be found as follows
|
Element |
Ratio by mass |
Atomic mass |
Mass ratio/atomic mass |
Simple ratio |
|
H
O |
1
8 |
1
16
|
`frac{1}{1}=1` `frac{8}{16}=frac{1]{2}` |
2
1 |
Thus the ratio by number of atoms
for water is H: O= 2:1
· The ratio by number of atoms for
an ammonia molecule can be found as follows
|
Element |
Ratio by mass |
Atomic mass |
Mass ratio/atomic mass |
Simple ratio |
|
N
H |
14
3 |
14
1
|
`frac{14}{14}=1` `frac{3}{1}=3` |
1
3 |
Thus, the ratio by number of
atoms for ammonia is N: H= 1:3
· The ratio by number of atoms for Carbon
dioxide molecule can be found as follows
|
Element |
Ratio by mass |
Atomic mass |
Mass ratio/atomic mass |
Simple ratio |
|
C
O |
3
8 |
12
16
|
`frac{3}{12}=frac{1]{4}`
`frac{8}{16}=frac{1]{2}` |
1
2 |
Thus, the ratio by number of
atoms for Carbon dioxide is C: O= 1:2
Explanation Activity 3.2 Class 9 Science
A compound
is formed when two or more elements react with each other. In the compound, the
proportion of constituent elements remains always constant.
Conclusion Activity 3.2
Class 9 Science
This activity explains ‘The law of constant Proportion’.
According to this law- In a chemical substance the elements are always present
in definite proportions by mass.
Related Topics for You
1. Previous Activity - Activity 3.1 Class 9 Science
2. Solution of Chapter 3 Atoms and Molecules
