CBSE Sample Papers for Class 10 Science Paper 3
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 3.
Time Allowed: 3 hours
Max. 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 three questions of three marks each, two questions of five marks each and one question
- (for assessing the practical skills) of two 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-d are five marks 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.
Although bile juice has no digestive enzyme it is still considered to be very important during digestion of food. Why?
Question 2.
Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?
Question 3.
State Modern Periodic Law. What is number of groups and periods in the Modern Periodic Table?
Question 4.
List four characteristics of the images formed by plane mirrors.
Question 5.
How is charcoal obtained from wood? Why is charcoal considered a better fuel than wood?
Question 6.
- What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?
- What type of reaction is this?
- Write a balanced chemical equation to represent the above reaction.
OR
A brown substance ‘X’ on heating in air forms a substance ‘Y’. When hydrogen gas is passed over heated ‘Y’, it again changes back into ‘X’.
- Name the substance ‘X’ and ‘Y’
- Name the type of chemical reactions occurring during both the changes.
- Write the chemical equations of the reactions.
Question 7.
Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas when passed through lime water, turns it milky. Identify A, B and C.
Question 8.
- What is meant by periodicity in properties of elements with reference to the periodic table?
- Why do all the elements of the same group have similar properties?
- How will the tendency to gain electrons change as we move from left to right across a period? Why?
Question 9.
Leaves of a healthy potted plant were coated with vaseline to block the stomata. Will this plant remain healthy for long? State three reasons for your answer.
OR
- Why do fishes die when taken out of water?
- Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Question 10.
- Write the functions of the following parts of human male reproductive system:
- Testis;
- Vas deferens;
- Urethra;
- Prostate
- List any two common pubertal changes that appear in human males.
Question 11.
Explain how the sex of the child is determined at the time of conception in human beings.
Question 12.
A chemical bond is an attractive force that holds the atoms together in a
molecule or a compound. The element carbon is known to have the unique ability to form bonds with other similar atoms or atoms of other elements. This property of carbon has resulted in having very large number of its compounds. The carbon-carbon bond is also known to be very strong and hence stable. · Answer the following questions based on above information:
- Name the chemical bond formed between carbon-carbon atoms. How is this bond formed?
- Which two values are reflected in the nature of carbon resulting in its ability to form maximum number of compounds?
- How can these values be helpful in strengthening relationship in a family, organisation or even people of a nation?
Question 13.
For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.
Question 14.
- Define the term ‘volt’.
- State the relation between work, charge and potential difference for an electric circuit.
Calculate the potential difference between the two terminals of a battery if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to the other.
OR
- Define the term ‘coulomb’.
- State the relationship between the electric current, the charge moving through a conductor and the time of flow.
Calculate the charge passing through an electric bulb in 20 minutes if the value of current is 200 mA.
Question 15.
AB is a current-carrying conductor in the plane of the paper as shown in figure. What are the directions of magnetic fields produced by it at points P and Q? Given r1 > r2, where will the strength of the magnetic field be larger?
Question 16.
- Distinguish between ionic and covalent compounds under the following properties:
- Strength of forces between constituent elements
- Solubility of compounds in water
- Electrical conduction in substances
- Explain how the following metals are obtained from their compounds by the reduction process:
- Metal M which is in the middle of the reactivity series.
- Metal N which is high up in the reactivity series. Give one example of each type.
OR
- Distinguish between “roasting’ and ‘calcination’. Which of these two is used for sulphide ores and why?
- Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
- Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure copper.
Question 17.
A salt X is formed and a gas is evolved when ethanoic acid reacts with sodium hydrogencarbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write chemical equation of the reaction involved. ,
Question 18.
How are involuntary actions and reflex actions different from each other?
OR
- Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?
- Sameer was studying in his room. Suddenly he smells something burning and sees smoke in the room. He rushes out of the room immediately. Was Sameer’s action voluntary or involuntary? Why?
Question 19.
- What is myopia? State the two causes of myopia. With the help of labelled ray diagrams show
- the eye defect myopia
- correction of myopia using a lens.
- Why is the normal eye unable to focus on an object placed within 10 cm from the eye?
Question 20.
Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse. Why is it that a burnt out fuse should be replaced by another fuse of identical rating?
Question 21.
Explain some harmful effects of agricultural practices on environment.
SECTION-B
Question 22.
Solid sodium bicarbonate was placed on a strip of pH paper. What was the change in colour?
Question 23.
You have four beakers A, B, C and D. Out of A and B one has hard water and the other has soft water. Out of C and D one has soap solution and the other has detergent solution. How would you identify these liquids?
OR
A gas is liberated immediately with a brisk effervescence, when you add acetic acid to sodium hydrogencarbonate powder in a test tube. Name the gas and describe the test that confirms the identity of the gas.
Question 24.
The following experimental set-ups were kept in the laboratory to show that ‘CO, is given out during respiration’.
After 2 hours, in which delivery tube does the water rise?
Question 25.
Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Write the first step from where such a type of reproduction begins. Draw first two stages of this reproduction.
Question 26.
Identify
- PQ
- NN2
- ∠LMR
- RS<
Question 27.
The current flowing through a resistor connected in an electrical circuit and the potential difference developed across its ends are shown in the given diagrams.
Find the value of resistance of the resistor in ohms.
Answer
SECTION-A
Answer 1.
Bile makes the medium alkaline for the action of pancreatic juice necessary for digestion.
Answer 2.
Yes, the constancy is maintained because cells in all these three structures undergo only mitotic divisions.
Answer 3.
Modern Periodic Law states that properties of elements are a periodic function of their atomic number. In Modern Periodic Table there arel8 groups and 7 periods.
Answer 4.
Following are the characteristics of the images formed by plane mirrors:
- Size of image is equal to size of object.
- Image formed is erect.
- Image formed is virtual.
- Image is laterally inverted.
- Object distance is equal to image distance. (Any four)
Answer 5.
Charcoal is obtained from wood by destructive distillation of wood.
Charcoal is considered a better fuel than wood because
- it has higher calorific value than wood.
- it does not produce any smoke on burning.
Answer 6.
- A yellow precipitate of lead iodide (Phl2) is formed.
- Precipitation reaction or Double displacement reaction
OR
- X— Cu ; Y— CuO.
- When copper is heated in air, oxidation takes place. When hydrogen gas is passed over heated copper oxide, reduction takes place.
- 2Cu + O2 \(\underrightarrow { \triangle }\) 2CuO (Oxidation)
CuO + H2 \(\underrightarrow { \triangle }\) Cu + H2O (Reduction)
Answer 7.
Baking powder (NaHCO3), Salt A is commonly used in bakery products. On heating, it forms sodium carbonate (Na2CO3), B and CO2 gas, C is evolved. When CO2 gas is passed through lime water it forms calcium carbonate (CaCO3), which is slightly soluble in water making it milky.
A — NaHCO3; B — Na2C03; C — CO2 gas
Answer 8.
- When the elements having similar chemical properties are repeated at a regular interval, this is known as periodicity of elements. In modern periodic table (which is based on atomic number), we see that the elements having similar chemical properties are repeated at a certain interval of atomic number.
- This is because the elements of same group have same number of valence electrons or they have similar electronic configuration. For example, all alkali metals (like sodium, potassium, etc.) have 1 valence electron.
- The tendency to gain electrons across a period from left to right increases. This is because the effective nuclear charge increases and consequently it becomes easier for the atoms to gain electrons.
Answer 9.
If waxy coating is made on the surface of leaf, loss of water in the form of
water vapour does not take place. Even the gaseous exchange will not take place. So, photosynthesis will either be reduced or will not take place. The plant will not remain healthy for long because:
- Exchange of gases will not take place.
- Photosynthesis will either be reduced or will not take place due to lack of CO2
- Transpiration will not take place, so there will be no mechanism of cooling in hot weather.
OR
- Fishes respire with the help of gills. Gills are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water. Since fishes cannot absorb gaseous oxygen they die soon after they are taken out of water.
- Aquatic organisms like fishes obtain oxygen from water present in
dissolved state through their gills. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial
organisms.
Answer 10.
-
- estis: It helps in the formation of sperm, germ cells and also it function in secretion of testosterone.
- Vas deferens: It aids in the delivery of sperms from testis to urethra
- Urethra: It is involved in the ejaculation of sperms.
- Prostate: Its secretions nourishes the sperms.
- Thick hair growth on the face, voice begins to crack, hair growth in armpits, etc. are common pubertal changes in a human male.
Answer 11.
In a human being, sex of a child is determined depending upon which kind of male gamete fertilises with the female gamete. There are 23 pairs of chromosomes in each of the maternal and paternal copy. Out of 23 pairs,
22 pairs are said to be autosomes Male Female (A) and one pair is called sex chromosomes in male XY and female XX). At the time of fertilisation, the egg cell fuses with the sperm cell to form the zygote. If the sperm carrying X Female Male chromosome fertilises an ovum carrying X chromosome, then the child born will be a girl. If the sperm carrying Y chromosome fertilises an ovum carrying X chromosome, the child born will be a boy.
Answer 12.
- Covalent bond is formed between carbon-carbon atoms by the sharing of electrons.
- Sharing (ability to share); nature to share and bonding with others.
- Sharing of one’s possessions, jobs, resources, moments with others enables an individual, an organisation or even a society to live happily and comfortably.
Answer 13.
A convex lens forms a virtual and erect image when the object is placed between the optical (O) centre and focus (F’).
Consider two rays starting from the top of the object. The ray (AP) going parallel to the principal axis after refraction passes through the focus (F). The ray (AO) passing through the optical centre passes through the lens un deviated. These refracted rays produced backwards as shown by dotted lines. They meet at A’. Draw perpendicular A’B’ on the principal axis. Thus A’B’ is the complete image of object AB.
Answer 14.
- I volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.
Therefore, 1 volt = \(\frac { 1\quad joule }{ 1\quad coulomb }\) - Work done = Charge × Potential difference
or, W = QV
or, \(V=\frac { W }{ Q } =\frac { 100J }{ 20C } =5V\)
OR
- The charge possessed by the body is said to be 1 coulomb, if 1 joule of work is done in moving a charged body across two points having a potential difference of 1 volt.
- Electric current is the rate of flow of electric charge. If Q coulombs of charge flows through a conductor in time t seconds, then the current I is given by
I = \(\frac { Q }{ t }\)
or Q = It
Given, I + 200mA = 200 × 60 s
t = 20 min = 20 × 60 s
using, Q = It
= 200 × 10-3 × 20 × 60
= 240C
Answer 15.
Magnetic field at P is into the plane of paper and at Q it is out of the plane of paper. The strength of the magnetic field at I will be larger as strength of the field α \(\frac { I }{ r }\)
Answer 16.
-
- (a)Ionic compounds have strong force of attraction between the oppositely charged ions (e.g., Na+ and Cl”), so they are solids. Covalent compounds have weak force of attraction between their molecules, so they are usually liquids or gases.
- (b)Ionic compounds are soluble in water but covalent compounds are insoluble in water.
- (c)Ionic compounds conduct electricity when dissolved in water or when melted because they contain ions (charged particles). But, covalent compounds like glucose do not conduct electricity because they do not contain ions.
- (a)The metal M which is in the middle of the reactivity series (such as iron, zinc, lead, copper, etc.) is moderately reactive. So, for obtaining such metals from their compounds, their sulphides and carbonates (in which they are present in nature) are first converted into their oxides by the process of roasting and calcination respectively. The metal oxides (MO) are then reduced to the corresponding metals by using suitable reducing agents such as carbon. For example, zinc metal from its oxide is obtained as follow:
- (b)The metal N which is high up in the reactivity series (such as sodium, magnesium, calcium, aluminium, etc.) is very reactive and cannot be obtained from its compound by heating with carbon.
Therefore, such metals are obtained by electrolytic reduction of their molten salt. For example, sodium is obtained by the electrolysis of molten sodium chloride (NaCl).
At cathode : Na+ + e– → Na
At anode : 2CI– → CI2 + 2e–
OR
1. Roasting : It is the process in which sulphide ores of the metals are converted into oxides by heating them in the presence of excess air. For example, zinc sulphide is converted into zinc oxide by roasting.
Calcination : It is the process in which carbonate ores of the metals are decomposed into oxides by heating them in the absence or limited air. For example, zinc carbonate is decomposed into zinc oxide and carbon dioxide by calcination.
Out of roasting and calcination, only roasting is used for sulphide ores. This is because it is easier to obtain metal from its oxide as compared to
its sulphide.
2.
3. Anode—Impure copper
Cathode—Strip of pure copper
Electrolyte—Acidified copper sulphate solution.
Answer 17.
X is sodium ethanoate.
Gas evolved is carbon dioxide.
Activity:
- Set up the apparatus as shown in the figure.
- Takeaspatula-fullofsodium hydrogencarbonate Ethanoic in a test tube and add 2 mL of dilute ethanoic acid.
- We observe that brisk effervescence of a gas is produced in the test tube.
- Now pass the gas produced through freshly prepared lime water. It is observed that lime water turns milky. Only carbon dioxide gas can turn lime water milky. So, this activity proves that when ethanoic acid reacts with sodium hydrogencarbonate, then carbon dioxide is evolved.
CH2COOH + NaHCO3 → CH3COONa + H2O + CO2
Answer 18.
S.No. | Involuntary actions | Reflex actions |
1. | They involve autonomic nervous system. | They involve all parts of voluntary nervous system. |
2. | They usually occur in response to internal stimuli. | They operate against harmful stimuli which are generally external and may cause injury. |
3. | They are connected with functioning of internal body parts. | They are connected with emergency. |
4. | These are regulated by medulla (hind-brain). | Reflex action is controlled by spinal cord. |
5. | The speed of response is slower. | The speed of response is very fast. |
6. | Example: Beating of heart muscle. | Example: Removal of hand with jerk when someone touches a hot object accidently. |
OR
- When an electrical signal reaches the axonal end of a neuron, it releases a chemical substance. This chemical diffuses towards the dendrite end of next neuron where it generates an electrical impulse or signal. Hence, the electrical signal is converted into a chemical signal at the axonal end. Since these chemicals are absent at the dendritic end of the neuron, the electrical signal cannot be converted into chemical signal.
- Sameer’s action was voluntary because rushing out of the room was under his conscious control. The smoke and smell were perceived by the receptors in the sense organs and signals are sent to the brain. The brain, then sent signals to the effector organs, i.e., the muscles, to move out of the room.
Answer 19.
- Myopia is the defect of the eye vision due to which a person can see the t o Retina near objects clearly but cannot see Rays from distant object the far objects so distinctly.
Causes of myopia: Myopia is caused :- due to the elongation of the eye Far point ball.
- due to decrease in the focal length Bringing the of the eye lens. The eye lens object close to eye becomes more
myopic eye Far point concave lens of suitable focal length in the spectacles of such a person.
2. The ability of the eye lens to adjust its focal length is called Use of concave lens accommodation. However, the Correction for myopia focal length of the eye lens cannot
be decreased below a certain limit. The maximum accommodation of a normal eye is reached when the object is at a distance of 25 cm from the eyes. Thus, the normal eye is unable to focus an object placed within 10 cm from the eye because all the power of accommodation has already been exhausted.
20.
A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. Otherwise, the appliances or the circuit may be damaged. When current in the circuit exceeds the value of fuse rating, the fuse wire burns due to overloading. This causes a gap in the circuit and the current stops flowing in the circuit.
This is done due to the reason so that the circuit or the appliances to be connected in the circuit continue functioning without any damage in future.
Answer 21.
Some harmful effects of agricultural practices on environment are:
- Excessive use of fertilisers changes the chemistry of soil and kills useful microbes.
- Excessive use of non-biodegradable chemical pesticides leads to biological magnification.
- Extensive cropping causes loss of soil fertility.
- Excess use of ground water for agriculture lowers the water table.
- Damage to natural ecosystem/habitat.
SECTION-B
Answer 22.
The colour of the pH paper did not change because pH paper shows colour depending on the hydrogen ion concentration in solution. Solid sodium bicarbonate does not produce hydrogen ions in its solid state thus does not give any colour on pH paper.
Answer 23.
On adding soap solution, lather will be formed in the beaker containing soft water only. On adding detergent solution lather will be formed by both hard and soft water.
OR
The liberated gas is carbon dioxide, CO2.
Lime water turns milky on passing CO2 through it.
Answer 24.
The water rises only in set-up A because the cotton plug used in set-up B does not create partial vacuum which makes the water rise in the beaker.
Answer 25.
The type of asexual reproduction is Binary Fission. The first step in binary fission is Elongation of cell and its nucleus.
Answer 26.
- Incident ray
- Angle of deviation
- Normal on AC
- Emergent ray
Answer 27.
Current, I = 180 mA = 180 × 10-3 A
Potential difference, V = 1.8 V
Resistance = v/1 = \(\frac { V }{ I } =\frac { 1.8 }{ 180\times 10^{ -3 } } 10\Omega \)
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