Class 7
Time:1hour
NATIONAL PUBLIC SCHOOL
WHITEFIELD, BENGALURU
TERM 2 – REVIEW WORKSHEET 1 - 2020 – 2021
CHEMISTRY
DATE:22.12.20
Max. Mks: 30
No. of Pgs.: 02
General Instructions:
 All questions are compulsory.
 The question paper consists of 18 questions divided into four sections: A, B, C and D.
 Section A contains 10 questions of 1 mark each.
 Section B contains 5 questions of 2 marks each.
 Section C contains 2 questions of 3 marks each.
 Section D contains 1 question of 4 marks.
SECTION A
1. Why is graphite used as an electrode in electrolytic cells?
2. Which property of metal makes them suitable for making wind chimes?
3. A non-metal ‘X’ dilutes the effect of oxygen.
(a) Identify the non-metal.
(b) State its importance for plants.
4. Why do silver objects turn black if exposed to air for a long time?
5. Name a metal which is liquid at room temperature. Explain how it is used in dentistry.
6. How is heating of platinum wire and melting of ice similar kind of change?
7. What is duralumin? How is it useful?
8. Given below are two processes. Classify them as physical and chemical change.
Germination of seeds
,
Cutting of hair
9. Define tensile strength.
10. Why burning of wood and cutting wood into small pieces are considered as two different
kinds of changes?
SECTION B
11. Which noble gas is used for filling weather observation balloons? State one reason why it is
preferred over other gases.
12. When a candle burns both physical and chemical changes take place. Justify the statement.
13. Define the term galvanisation. What is the purpose of galvanising?
P.T.O
14. State one example for each of the following statements.
(a) Metals are generally malleable.
(b) Heat is usually given off or absorbed during a chemical change.
15. Define melting point. How is the melting point of an object related to the force of attraction
between its molecules?
SECTION C
16. Explain the composition of Brass. Write one of its special property. State any one use.
17. What happens when mercuric oxide is heated? Draw a labelled diagram to illustrate the
changes that take place when mercuric oxide is heated.
SECTION D
18. A student was gifted a new bicycle on his birthday. After few months, he found that the
cycle chain and even the handle had a brown flaky deposit. His elder brother advised him to
apply a coat of paint to the handle and oil to the chain of his cycle.
Answer the following questions:
(a) What was the brown flaky substance? Write a chemical equation to explain the process.
(b) Explain how applying a coat of paint and oiling would help.
(c) What is the value shown by the student’s brother?
*****************************************