# CBSE Sample Papers for Class 10 Science Paper 6

## CBSE Sample Papers for Class 10 Science Paper 6

These Sample papers are part of CBSE Sample Papers for Class 10 Science. Here we have given CBSE Sample Papers for Class 10 Science Paper 6.

Time allowed: 3 hours
Maximum marks : 80

General Instructions

• The question paper comprises two sections, A and B. You are to attempt both the sections.
• All questions are compulsory.
• All questions of Section-A and B are to be attempted separately.
• There is an internal choice in two questions of three marks each and one question of five marks.
• Question numbers 1 and 2 in Section-A are one mark question. They are to be answered in one word or in one sentence.
• Question numbers 3 to 5 in Section-A are two marks questions. These are to be answered in 30 words each.
• Question numbers 6 to 15 in Section-A are three marks questions. These are to be answered in about 50 words each.
• Question numbers 16 to 21 in Section-A are 5 mark questions. These are to be answered in 70 words each.
• Question numbers 22 to 27 in Section-B are based on practical skills. Each question is a two marks question. These are to be answered in brief.

SECTION – A

Question. 1.
What are biodegradable substances ? Give two examples.

Question. 2.
What does the peripheral nervous system consist of ?

Question. 3.
What are isotopes ?

Question. 4.
What is Snell’s law of refraction ?

Question. 5.
Compare natural and artificial ecosystems ?

Question. 6.
What is the principle on which an electric motor works ? What are the special features of commercial electric motors ?
OR
A wire of length L and resistance R is stretched so that its length is doubled and the area of cross-section is halved. How will its :
(a) resistance change ?
(b) resistivity change ?

Question. 7.
List the properties of magnetic lines of force.

Question. 8.
What is amalgam ? What are the benefits of alloying ?

Question. 9.
Is it necessary to mention the physical states of the reactants and products in a chemical equation. Explain with an example.

Question. 10.
Describe the ovary of the flower with a labelled diagram.
OR
What is the role of seminal vesicles and prostrate gland ?

Question. 11.
How does phototropism occur in plants ?

Question. 12.
If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished what kind of lens is it? Justify with a ray diagram. If the power of the lens is -10 D, what is its focal length?

Question. 13.
Show the formation of chlorine molecule using electron dot structure.
OR
What is the role of metal of reagents written on arrows in the given chemical reactions ?

Question. 14.
Why should we use our resources judiciously ?

Question. 15.
Why are platelets needed by our body ?

Question. 16.
Name the type of mirror used in the following situations :
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.

Question. 17.
How could the Modem Periodic Table remove various anomalies of Mendeleev’s Periodic Table ?
OR
What were the limitations of Mendeleev’s periodic table ?

Question. 18.
What is the response of plants to stimuli known as ? Describe the different types of these movements.

Question. 19.
What is Ohm’s law ? Draw the circuit for verifying Ohm’s law. If you draw a graph between the potential difference and the current flowing through a metallic conductor, what kind of curve will you get ? Explain how would you use this graph to determine the resistance of the conductor ?

Question. 20.
Discuss the properties of ionic compounds with regard to their melting and boiling point and conduction of electricity.

Question. 21.
What is hydroelectricity or hydel electricity ? What should one has to keep in mind while constructing a dam ?
OR
What is the importance of forest as a resource ? What are the causes of deforestation ?

SECTION – B

Question. 22.
Why does silver turn black when exposed to air ?

Question. 23.
What happens when dry slaked lime [Ca (OH)2] reacts with chlorine ? What is the product used for ?

Question. 24.
Draw a labelled diagram of the human brain. What is the function of the medulla ?

Question. 25.
Which of the following actions we should adopt and why ?

(a) Taking a bus or using your personal vehicle.
(b) Using ordinary bulbs or LED bulbs in your homes.
(c) Taking the stairs or using the lift.
(d) Wearing extra woollen clothes or using the heater.

Question. 26.
Find the least count of a milliammeter in which there are 20 divisions between 400 mA and 500 mA marks.
OR
While experimentally verifying Ohm’s law, a student observed that the pointer of the voltmeter coincides with 15th division when the voltmeter has a least count of 0.05 V. Find the observed reading of voltmeter.

Question. 27.
Raju places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the image of the flame on a screen. Then he slowly moves the flame towards the lens and each time gets the image on the screen.

(a) In which direction from the lens, does he move the screen to focus the image ?
(b) What is the change in the size of the image ?
(c) How does the intensity of the flame change as the flame moves towards the lens ?
(d) At what point approximately between the flame and the lens will the image be inverted and of the same size ?

SECTION – A

Biodegradable substances are those substances that can be broken down by biological processes. Some examples are remains of plants and animals and vegetable wastes that our houses produce daily.

The peripheral nervous system consists of the cranial nerves and the spinal nerves. While cranial nerves arise from the brain, the spinal nerves arise from the spinal cord.

Isotopes are atoms of elements having different mass numbers or atomic mass but the same atomic numbers.

According to Snell’s law of refraction, the ratio of sine of angle of incidence to the sine of angle of refraction is constant for a given pair of media.
sine of angle of incidence / sine of angle of refraction = constant
OR
$$\frac { sin\quad i }{ sin\quad r }$$ = constant = n
This constant is called refractive index.

Natural ecosystems are the ones found in nature such as forests, ponds and lakes. Artificial ecosystems are man-made such as gardens and crop-fields.

A motor works on the principle that when a rectangular coil is placed in a magnetic field and current is passed through it, a force acts on the coil which rotates it continuously. When the coil rotates, the shaft attached to it also rotates. In this way the electrical energy supplied to the motor is converted into the mechanical energy of rotation. Electric motor is an important component in electric fans, refrigerators, mixers, washing machines, computers and mp3 players.
The commercial motors use :
(a) An electromagnet in place of the permanent magnet.
(b) Large number of turns of the conducting wire in the current-carrying coil.
(c) A soft iron core on which the coil is wound and the coils is called an armature. The soft iron core becomes magnetised and increases the strength of magnetic field. This makes the motor more powerful.
OR
(a) Here, length is doubled and area of cross-section is halved. Thus, a wire of length l and area of cross-section A becomes a wire of length 2l and area of cross-section $$\frac { A }{ 2 }$$

i.e., resistance becomes four times.
Resistivity of a substance does not depend on its length or area of cross-section. It depends on the nature of the material and temperature. Hence, there is no change.

Properties of magnetic field lines :

1. Magnetic field lines follow the direction from the North Pole to the South Pole.
2. Magnetic field lines always form closed circular loops.
3. Magnetic field lines do not cross one another.
4. Closer the field lines; stronger is the magnetic field and vice-versa.
5. Magnetic field lines are closer near the poles; which shows greater strength of magnetic field near the poles.

Amalgam is an alloy in which one of the constituent metal is mercury. Alloying is a good method of improving the properties of a metal. An alloy can have the properties of its constituents. An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. The electrical conductivity and melting point of an alloy is less than that of pure metals. Iron is a widely used metal. Usually iron in its pure state is very soft and easily stretched. When mixed with a little carbon it becomes hard and strong. Similarly when iron is mixed with nickel and chromium it produces stainless steel which is hard and resistant to rust. Solder, an alloy of lead and tin has a low melting point and is used for welding electrical wires together. Brass, an alloy of copper and zinc and bronze, an alloy of copper and tin are not good conductors of electricity though copper is used for making electrical circuits.

A chemical equation can be made more informative by mentioning the physical states of the reactants and products along with their chemical formulae. The gaseous, liquid, queous, and solid states of the reactants and products are represented by the notations, (g), (1), (aq) and (s) respectively. The word aqueous is written if the reactant or product s present as a solution in water. When we use the symbol (g) with H2O it means in the reaction water is used as steam.
Example : 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
In the above example, Fe in the solid state reacts with water in steam form and forms iron oxide in solid form and releases hydrogen gas.

The carpel is the female reproductive part of the flower which is present in the centre of the flower. It ^ consists of three parts. The upper part which is sticky and is called the stigma, the middle elongated part is called the style and the swollen bottom part is called ovary. The ovary contains the ovules and each ovule has an egg inside. The male germ-cell produced by the pollen grain fuses with the female germ cell in the ovule. This is called fertilisation and it results in the formation of the zygote. This zygote grows into a new plant.

The sperms are formed in the testes which are located outside the abdominal cavity. The sperms formed are delivered through the vas deferens which unites with a tube coming from the urinary bladder. The urethra is thus a common passage for both the sperms and urine. Seminal vesicles and prostate gland are two glands associated with the male reproductive system. These glands produce secretions that are added to the sperm during its movement through the vas deferens. The secretions provide a fluid medium to facilitate easy movement of the sperms and they also nourish the moving sperms. It is primarily the tail of the sperm which helps it in swimming in this fluid medium.

Phototropism means the response of plant parts towards sunlight. Here sunlight is the stimulus, while the shoot system responds positively to sunlight the root system responds negatively to sunlight. Different plant hormones help to coordinate growth, development and responses to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action. When growing plants detect light, a hormone called auxin which is synthesised at root tips helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of the auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light.

If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished, it is a concave lens.

As f has negative value so, it is a concave lens.

Chlorine atom has the atomic number 17. This means it has 17 electrons too. Its electronic configuration is 2,8 and 7. So it has a valency of 7. Now 2 chlorine atoms combine to form a chlorine molecule. Each atom is 1 short of the stable configuration. This is set right by sharing 1 electron each between the 2 atoms. Thus a single covalent bond is formed between the 2 chlorine atoms.

OR
(a) Ni acts as a catalyst.
(b) Concentrated H2SO4 acts as a catalyst.
(c) Alkaline KMnO4 acts as an oxidising agent.

All the things we use or consume like food, clothes, our shelter, books, toys, furniture, tools and vehicles are obtained from resources on this earth. The only thing we get from outside is the energy from the sun. This too is processed by the living organisms and various physical and chemical processes on the earth before we can use it. We should use resources judiciously because they are limited. We have an ever-increasing human population due to improved health care and this has brought about an increased demand for all the resources. The management of natural resources requires a long-time perspective so that they will last for the future generations and will not be exploited over a short period of time. Resource management must be focussed on an equitable distribution of resources so that it is not just a handful of rich and powerful people who benefit from this. In addition, when we extract these resources we must ensure a safe disposal of the wastes too. This is called sustainable natural resource management.

Platelets or thrombocytes are one of the constituents of blood the other two being the red blood corpuscles or erythrocytes and white blood corpuscles or leucocytes. Whenever there is an injury in the body bleeding starts. The body cannot afford to lose blood. In addition, leakage of blood leads to a drop in pressure which affects the pumping of the heart. To avoid this the body immediately informs the platelets to reach the site of injury. The platelets that keep circulating in the body quickly reach the site of bleeding and form a barrier or plug which stops the bleeding. That is why platelets are needed by our body.

(a) Concave mirror (b) Convex mirror (c) Concave mirror.
Explanation:

(a) Concave mirror is used in the headlights of a car. This is because concave mirrors can produce powerful parallel beam of light when the light source is placed at their principal focus. This powerful beam of light helps us to see things upto a considerable distance in the darkness of night.
(b) Convex mirror is used in side/rear view mirror of a vehicle. Convex mirrors give a virtual, erect, and diminished image of the objects placed in front of it. Because of this, they have a wide field of view. It enables the driver to see most of the traffic behind him/her.
(c) Concave mirrors are convergent mirrors. That is why they are used to construct solar furnaces. When solar furnace is placed at focus of concave mirror, sun rays after reflection from its surface gets converged at focus with much intense heat and solar furnace gets very hot.

Modem Periodic Table removes various anomalies of Mendeleev’s Periodic Table on the following points :

1. Position of isotopes : As Modem Periodic Table is based on atomic number, isotopes can be placed at one place in same group in Modem Periodic Table.
2. Anomalous Position of some pair of elements: In Mendeleev periodic table, some of the elements having higher atomic mass are placed before the elements having lower atomic mass. This defect of Mendeleev periodic table was overcome in Modem periodic table since it is based on atomic numbers.
3. Prediction of new elements: In long form of periodic table, the position and properties of new elements can be predicted easily on the basis of their atomic numbers or electronic configuration.

OR
The limitations of Mendeleev’s periodic table are as follows :

1. Hydrogen could not be given a fixed position. Electronic configuration of hydrogen is similar to alkali metals. It was able to combine with halogens, oxygen and sulphur to form compounds having similar formulae. Hydrogen could also exist as diatomic molecules just like halogens and could combine with metals and non-metals to form covalent compounds.
2. There was confusion regarding isotopes. Isotopes were discovered long after Mendeleev had done his periodic classification. Isotopes of an element have similar chemical properties but different atomic masses.
3. Atomic masses do not increase in a regular manner in going from one element to the next. Hence it was not possible to predict how many elements could be discovered between two elements.

Plants show two different kinds of movements one dependent on growth and the other independent of growth. The response of plants to stimuli is called trophic movements. The word tropism means response to stimuli. Though plants do not have an elaborate nervous system they do respond to a variety of stimuli. Response of plants to the stimulus of light is known as phototropism. The stem and its parts are phototrophic. The response of plants to water is known as hydrotropism. Roots respond to the presence of water by growing towards it. Response to gravitational pull is called geotropism. Roots are geotropic. Response of plants or their parts to the stimulus of touch is called thigmotropism. Some plants like the pea plant are very tender and climb up on supports for their growth. When their tendrils come in contact with any support, the tendrils immediately curl round the support and get a good grip.

Ohm’s law states that the electric current flowing through a metallic wire is directly proportional to the potential difference V across its ends provided its temperature remains the same.
In other words V α I
or
V/I = constant = R
or
V = I × R
Where R is a constant for a given metallic wire and is called its resistance.

If a graph is drawn between the potential difference (V) and current (I) the graph is found to be a straight line passing through the origin. This clearly shows that current is directly proportional to the potential difference. So the ratio V/I is a constant. This is the resistance of the conductor. The gradient of the straight line graph represents the resistance of the conductor.

Ionic compounds are formed by the transfer of electrons from one atom to another in an effort to get the stable electronic configuration in their outermost shell. The bond formed is called electrovalent bond and the atoms in that are either positive or negative ions. These ions are held together by strong forces of attraction. Hence ionic compounds are usually solids.

1. Ionic compounds have high melting and boiling points this means a lot of energy is required to break the strong inter-ionic attraction.
2. A solution of ionic compounds contains ions which move to the oppositely charged electrodes when current passes through the solution. Ionic compounds do not conduct electricity in the solid state as ions cannot move about. Ionic compounds conduct electricity in the molten state as the electrostatic forces between the ions is overcome by the heat.

Hydroelectricity or hydel electricity is the generation of electricity using the power of water. It is a means to generate electricity either from the kinetic energy of flowing water or the potential energy of falling water. In our country we primarily focus on storing huge quantities of water by building dams across rivers. The water from the high levels in the dam is carried through pipes to a turbine at the bottom of the dam. As rains regularly fill up the dams one need not worry about the generation of electricity. However while constructing dams one has to keep in mind a few things.

1. Not to affect large areas of agricultural land.
2. To safeguard the human habitation around the dam.
3. To ensure that vegetation is not submerged under water in the dams giving rise to air pollution on rotting.

OR
Forests are an important natural resource due to following reasons :

1. Forests provide us wood, dry fruits, spices, gums, resins, dyes, tannins and various products like honey, camphour, rubber etc.
2. The roots of trees hold the soil firmly preventing soil erosion.
3. It absorbs carbon dioxide from atmosphere and release oxygen which is life supporter.
4. It absorbs carbon dioxide which is a greenhouse gas thus plays an important role in reducing global warming.
5. It increases frequency of rainfall and regulates water cycle.
6. It serves as a shelter for wild life.

Causes of deforestation are :

1. Large scale deforestation for demand of wood, timber as raw materials for industries, domestic purposes etc.
2. Construction of dams, reservoirs, roads, railways.
3. Setting up of factories and industries.
4. Construction of big apartments to provide space to the growing population.
5. Shifting cultivation for agriculture.
6. Over-grazing by livestock.

SECTION – B

Silver turns black when exposed to air because it undergoes oxidation and forms silver oxide.
2Ag(s) + O2 (g) → 2AgO(s)

When dry slaked lime Ca(OH)2 reacts with chlorine it forms bleaching powder.
Ca(OH)2 + Cl2 → CaOCl2 + HO
Bleaching powder is used as a bleaching agent in textile industry and laundry units as a disinfectant, as an oxidising agent in chemical industries and in bleaching wood pulp in paper factories.

The medulla controls several involuntary actions like salivation, vomiting, blinking of the eye and blood pressure.

(a) We should take the public transport because it would save fuel.
(b) We should use LED bulbs in my house because it will help conserve electricity and bring down the electric bills.
(c) We should take the stairs because it would be good physical exercise for us and we can save on electricity.
(d) We should prefer wearing extra woollen clothes to using the heater because this saves electricity.