CLASS VII - SCIENCE - WORKSHEET-3, MATTER AROUND US - ANSWERS

 WORKBOOK - 3

MATTER AROUND US

I. Multiple choice questions.

1. Among the following statements, which one is wrong about an atom?

Ans: d. An atom is indivisible


2. Which of the following element is not in the top three most abundant atoms on the earth?

Ans: b. Hydrogen


3. Which of the following is an element?

Ans: b. Sulphur


4. The elements like magnesium and phosphorous are used in_______

Ans: b. Making crackers


II. Match the following

5. Match the molecules with their Ball and Stick models

  1.  Hydrogen chloride


  1. Carbon dioxide

  1. Ammonia


III. Fill in the blanks:

6. There are 118 elements till date. Among these_______ elements occur naturally and _______ elements are synthesised artificially in the laboratory.

Ans: 94 and 24


7. The most abundant type of atom in the universe is _________.

Ans: Hydrogen atom


IV. Answer briefly:

8. Decode the given molecular diagram into a chemical equation.

9. Classify the following molecules as moles of element or moles of compound.

Ans:

Element Compound

P4 HNO3

S8 H3PO4

Cl2 CH4


10. Sodium is a corrosive metal. Chlorine is a poisonous gas. But, sodium chloride (Common salt) , the compound formed from these elements is an essential ingredient in our food. Justify sodium chloride is safe to use based on the properties of compounds.

Ans: 

  • Sodium chloride is a compound.

  • The compound composed of these ions exhibits properties entirely different from the properties of the elemental sodium and chlorine.

  • So it is safe to use sodium chloride in our food.

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