NCERT Class-9 Science Solutions: Chapter 3-Atoms And Molecules Part 11

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Question 44:

Fill in the blanks

  1. In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called ————.

  2. A group of atoms carrying a fixed charge on them is called ————.

  3. The formula unit mass of is ————.

  4. Formula of sodium carbonate is ———— and that of ammonium sulphate is ————.

Answer:

  1. In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called Low of conservation of mass.

    Image of Law of Conservation of mass

    Image of Law of Conservation of Mass

    Image of Law of Conservation of mass

  2. A group of atoms carrying a fixed charge on them is called polyatomic ion.

  3. The formula unit mass of is .

  4. Formula of sodium carbonate is and that of ammonium sulphate is .

Question 45:

Complete the following crossword puzzle (Fig.) by using the name of the chemical elements. Use the data given in Table.

Across and Down
Across And Down

Across

Down

2. The element used by Rutherford

during his α–scattering

experiment

1. A white lustrous metal used for

making ornaments and which

tends to get tarnished black in

the presence of moist air

3. An element which forms rust on

exposure to moist air

4. Both brass and bronze are alloys

of the element

5. A very reactive non–metal stored

under water

6. The metal which exists in the

liquid state at room temperature

7. Zinc metal when treated with

dilute hydrochloric acid

produces a gas of this element

which when tested with burning

splinter produces a pop sound.

8. An element with symbol Pb

Result for crossword puzzle by using the name of the chemical elements (Q)

Crossword Puzzle by Using the Name of the Chemical Elements (Q)

Result for crossword puzzle by using the name of the chemical elements (Q)

Answer:

Result for crossword puzzle by using the name of the chemical elements (A)

Crossword Puzzle by Using the Name of the Chemical Elements (A)

Result for crossword puzzle by using the name of the chemical elements (A)