Class X (CBSE 2019) Science Delhi (Set-3)

General Instructions:

1. The question paper comprises five sections, A, B, C, D and E. You are to attempt all the sections.
2. All questions are compulsory.
3. Internal choice is given in sections B, C, D and E.
4. Question numbers 1 and 2 in Section A are one mark questions. They are to be answered in one word or in one sentence.
5. Question numbers 3 to 5 in Section B are two-marks questions. These are to be answered in about 30 words each.
6. Question numbers 6 to 15 in Section C are three-marks questions. These are to be answered in about 50 words each.
7. Question numbers 16 to 21 in Section D are five-marks questions. These are to be answered in about 70 words each.
8. Question numbers 22 to 27 in Section E are based on practical skills. Each question is a two marks question. These are to be answered in brief.

Question 1

If you could use any source of energy for heating your food which one would you prefer? State one reason for your choice.

SOLUTION:

Natural gas can be used for heating and cooking food because it is a clean source of energy. It does not produce a huge amount of smoke on burning. Although it is highly inflammable, it is easy to use, transport and it produces a huge amount of heat on burning.

Question 2

Write the function of voltmeter in an electric circuit.

SOLUTION:

The function of the voltmeter in a circuit is to measure the voltage drop across any appliance. The voltmeter is always connected parallel in the circuit.

Question 3

What happens to the image distance in the normal human eye when we decrease the distance of an object, say 10 m to 1 m? Justify your answer.

SOLUTION:

If the object distance is greater than 25 cm the image is always formed on the retina as the focal length of the human eye lens gets adjusted depending on the object distance. This special property of human eye is called as power of accommodation. Hence, image distance will remain same if object distance changes from 10 m to 1 m.

Question 4

List two different functions performed by pancreas in our body.

SOLUTION:

The pancreas contains both the endocrine and exocrine portions. The exocrine region secretes sodium bicarbonate and many digestive enzymes. The pancreatic amylase causes breakdown of starch, pancreatic lipase causes breakdown of lipids, and trypsin causes digestion of proteins The endocrine regions secrete hormones i.e. insulin and glucagon. These hormones regulate the level of glucose in the blood. Insulin decreases while glucagon increases the blood glucose level.

Question 5

How it can be proved that the basic structure of the Modern Periodic Table is based on the electronic configuration of atoms of different elements?

OR

The electronic configuration of an element is 2, 8, 4. State its:

1. group and period in the Modern Periodic Table.

(b) name and write its one physical property.

SOLUTION:

Modern periodic law states that the physical and chemical properties of an element in the periodic table are the periodic function of the atomic number of that element. Electronic configuration of the elements plays an important role in the placement of elements in the modern periodic table. The valence shell electron of an element decides its position in a particular group or period.