Science Delhi Set 3 2009-2010 English Medium Class 10 Question Paper Solution

Name the part of our eyes which helps us to focus near and distant objects in quick succession.

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror: 

 What will be the focal length of this mirror?

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror: 

 Which type of spherical mirror will it provide? 

What is the nature of image formed by a concave mirror if the magnification produced by the mirror  

 +4 

A charged particle enters at right angles into a uniform magnetic field as shown: 

What should be the nature of charge on the particle if it begins to move in a direction pointing vertically our of the page due to its interaction with the magnetic field?  

On what basis is a chemical equation balanced?

State two characteristic features of carbon which when put together give rise to a large number of carbon compounds.

Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.

What are fossil fuels?

Write two disadvantages of burning fossil fuels.

Two coils A and B of insulated wire are kept close to each other. Coil A is connected to a galvanometer while coil B is connected to a battery through a key. What would happen if: 

the current is stopped by removing the plug from the key? 

Explain your answer mentioning the name of the phenomenon involved. 

Two coils A and B of insulated wire are kept close to each other. Coil A is connected to a galvanometer while coil B is connected to a battery through a key. What would happen if: 

a current is passed through coil B by plugging the key?  

Explain your answer mentioning the name of the phenomenon involved.

What is a solenoid?

Draw the pattern of magnetic field lines of a solenoid through which a steady current flows. What does the pattern of field lines inside the solenoid indicate?

What is Hypermetropia (far sightedness)? 

Draw a ray diagram to show how Hypermetropia is defect can be corrected using a lens.

Mention any four limitations in harnessing wind energy on a large scale.

At what distance should an object be placed from a lens of focal length 25 cm to obtain its image on a screen placed on the other side at a distance of 50 cm from the lens? What will be the magnification produced in this case?

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electron shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound. This ionic compound is added in a small amount to almost all vegetables and dishes during cooking. Oxides of elements A and B are basis in nature while those of elements E and F acidic. The oxide of element D is, however, almost neutral. Based on the above information, answer the following questions:

(a) To which group or period of the periodic table do these elements belong?
(b) What would be the nature of compound formed by a combination of elements B and F?
(c) Which two of these elements could definitely be metals?
(d) Which one of the eight elements is most likely to be found in gaseous state at room temperature?
(e) If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write formula of the compound formed by the combination of C and G.

No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.

(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.

(ii) Mention any two types of reactions under which above chemical reaction can be classified.

Name the functional group of organic compounds that can be hydrogenated. With the help of a suitable example, explain the process of hydrogenation, mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.

Derive the expression for the heat produced due to a current ‘I’ flowing for a time interval ‘t’ through a resistor ‘R’ having a potential difference ‘V’ across its ends. With which name is the relation known? How much heat will an instrument of 12W produce in one minute if it is connected to a battery of 12V?

Explain with the help of a labelled circuit diagram how you will find the resistance of a combination of three resistors, or resistance R₁, R₂ and R₃, joined in parallel. Also mention how you will connect the ammeter and the voltmeter in the circuit when measuring the current in the circuit and the potential difference across one of the three resistors of the combination.

Write the names and symbols of two very reactive metals belonging to group 1 of the periodic table. Explain by drawing electronic structure, how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.

What is meant by refining of a metal? Name the most widely used method for the refining of impure metals obtained by various reduction processes. Describe this method with the help of a labelled diagram by taking the example of any metal.

Name the hormone that helps in regulating level of sugar in our blood. Name the gland that secrets it.

A person lives near a forest. Make a list of four items which he can get from the forest to meet his daily needs.

Name the green dot like structures in some cells observed by a student when a leaf peel was viewed under a microscope. What is this green colour due to?

What is phototropism?

Describe an activity to demonstrate phototropism.

List any two differences between pollination and fertilisation.

Give one example each of characters that are inherited and the ones that are acquired in humans. Mention the difference between the inherited and the acquired characters.

How is ozone formed in the higher level of atmosphere?

 “Damage to the ozone layer is a cause of concern”. Justify this statement.

Write the full form of DNA.

Name the part of the cell where DNA is located?

Explain the role of DNA in the process of reproduction of the cell.

Explain the process of digestion of food in mouth, stomach and small intestine in human body.

 List the three events that occur during the process of photosynthesis. Explain the role of stomata in this process.

Describe an experiment to show that “sunlight is essential for photosynthesis”.