Students must start practicing the questions from CBSE Sample Papers for Class 10 Science with Solutions Set 5 are designed as per the revised syllabus.
CBSE Sample Papers for Class 10 Science Set 5 with Solutions
Time: 3 Hours
Maximum Marks: 80
General Instructions:
- This question paper consists of 39 questions in 5 sections.
- All questions are compulsory. However, an internal choice is provided in some questions. A student is expected to attempt only one of these questions.
- Section A consists of 20 objective type questions carrying 1 mark each.
- Section B consists of 6 Very Short questions carrying 02 marks each. Answers to these questions should be in the range of 30 to 50 words.
- Section C consists of 7 Short Answer type questions carrying 03 marks each. Answers to these questions should be in the range of 50 to 80 words.
- Section D consists of 3 Long Answer type questions carrying 05 marks each. Answer to these questions should be in the range of 80 to 120 words.
- Section E consists of 3 source-based/case-based units of assessment of 04 marks each with sub-parts.
Section – A
Select and write the most appropriate option out of the four options given for each of the questions 1 – 20.
There is no negative mark for incorrect response.
Question 1.
What is not a characteristic of a rear view mirror on a car?
(a) Convex in nature
(b) Concave in nature
(c) They have wider field of coverage
(d) They give a virtual image
Answer:
(b) Concave in nature
Explanation: As rear view mirror is a concave mirror. It has wider field of coverage and gives a 1 virtual, erect and diminished image of an object.
Question 2.
What principal should be consider when balancing chemical equations?
(a) Conservation of momentum
(b) Conservation of mass
(c) Conservation of energy
(d) Conservation of frequency
Answer:
(b) Conservation of mass
Explanation: The law of conservation of mass states that “mass can neither be created nor destroyed.” So, both sides of the chemical reactions have to be balanced to ensure that this law is followed and thus, the number of the reactant and the product molecules remains the same on both sides of the equation.
Question 3.
In the given diagram, How does the rectangular loop carrying a current i, behave when placed near a long straight wire that is parallel to one side of the loop and lies in the same plane as the loop?
(a) Rotate about an axis parallel to the wire
(b) Move towards the wire
(c) Move away from the wire or towards right
(d) Remains stationary
Answer:
(b) Move towards the wire
Explanation:
Question 4.
Which of the following is function of pancreatic juice?
(a) Trypsin digests proteins and lipase digests carbohydrates.
(b) Trypsin digests emulsified fats and lipase digests proteins.
(c) Trypsin and lipase digest fats.
(d) Trypsin digests proteins and lipase digests emulsified fats.
Answer:
(d) Trypsin digests proteins and lipase digests emulsified fats.
Explanation: Pancreatic juice contains the digestive enzymes amylases, lipases, and trypsin, which are secreted by the pancreas. Amylase degrades starch, trypsin degrades proteins, and lipase degrades emulsified lipids.
Question 5.
Which of the following is used for the dissolution of gold?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia
Answer:
(d) Aqua regia
Explanation: Aqua regia is a mixture of hydrochloric acid and nitric acid in a ratio 3 : 1 and it can dissolve noble metals such as gold, palladium, and platinum, which, however are not soluble in either of the acids alone.
Question 6.
An electric bulb is rated 220 V and 100 W. When it is operated at 110 V, the power consumed will be:
(a) 100 W
(b) 75W
(c) 50 W
(d) 25W
Answer:
(d) 25 W
Explanation:
We know that,
P= \(\frac{\mathrm{V}^2}{\mathrm{R}}\)
Where, P = Electric power
V = Potential difference in a circuit
R = Resistance
Now, R = \(\frac{\mathrm{V}^2}{\mathrm{P}}\)
R = \(\frac{220 \times 220}{100}\) = 484 Ω
As the voltage drop across the bulb is 110 V. The power consumed by the bulb is:
Pb = \(\frac{\mathrm{V}^2}{\mathrm{R}}\)
= \(\frac{110 \times 110}{484}\)
Pb = 25 W
Hence, the power consumed will be 25 W.
Question 7.
Offspring formed by the asexual method of reproduction have greater similarity among themselves because:
(i) Asexual reproduction involves only one parent.
(ii) Asexual reproduction does not involve gametes.
(iii) Asexual reproduction occurs before sexual reproduction.
(iv) Asexual reproduction occurs after sexual reproduction.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
Answer:
(a) (i) and (ii)
Explanation: Offspring have greater similarity as only one parent is involved in asexual reproduction thus no gametes are formed. The basis of asexual reproduction is mitosis (division of a nucleus into two identical daughter nuclei). Each daughter nucleus has same genetic make up because of replication of parental DNA. The new offspring produced are called clones.
Question 8.
Study the following diagram depicting the process of regeneration in a planarian flatworm. Which option correctly represents the different stages of regeneration shown in the diagram?
(a) A: New tissue formation and functional recovery, B: Initial injury, C: Blastema formation and cell division.
(b) A: Blastema formation and cell division, B: New tissue formation and functional recovery, C: Initial injury.
(c) A: Initial injury, B: Blastema formation and cell division, C: New tissue formation and functional recovery.
(d) A: Blastema formation and cell division, B: Initial injury, C: New tissue formation and functional recovery.
Answer:
(a) A: Initial injury, B: Blastema formation and cell division, C: New tissue formation and functional recovery.
Explanation: The correct sequence of stages shown in the diagram is:
(a) Initial injury: This is the stage where the flatworm is damaged or injured, leading to tissue loss or disruption.
(b) Blastema formation and cell division: After the initial injury, specialized cells called blastemal cells gather at the injury site. These cells undergo rapid division, forming a mass of undifferentiated cells known as blastema. The blastema serves as the source for regenerating new tissues.
(c) New tissue formation and functional recovery: The blastemal cells differentiate and undergo further cell division to regenerate specific tissues, such as muscle, nerves, and digestive structures. Over time, these newly formed tissues develop and integrate into the existing structures, resulting in functional recovery of the damaged area.
Question 9.
What is the colour of the ash formed when a magnesium ribbon is burnt in the air?
(a) White
(b) Black
(c) Yellow
(d) Pink
Answer:
(a) White
Explanation: When the magnesium ribbon is burned in the air, it bums with the white dazzling I flame leading to the formation of the white colour ash, which is magnesium oxide.
Question 10.
The equivalent resistance of a series combination of two resistances is X ohm. If the resistances are of 10 Ω and 40 Ω respectively, the value of X will be:
(a) 10 Ω
(b) 20 Ω
(c) 50 Ω
(d) 40 Ω
Answer:
(c) 50 Ω
Explanation: We know that
Total Resistance
R = R1 + R2
= 10 + 40
= 50 Ω
Hence, the value of X is 50 Ω.
Question 11.
In which of the following groups of organisms, the food material is broken down outside the body and absorbed ?
(a) Mushroom, green plants, amoeba
(b) Yeast, mushroom, bread mould
(c) Paramecium, amoeba, cuscuta
(d) Cuscuta, lice, tapeworm
Answer:
(b) Yeast, mushroom, bread mould
Explanation: Yeast, mushrooms, and bread mould all exhibit a saprophytic mode of nutrition. They use digestive enzymes secreted outside their body to break down complex organic substances and absorb basic molecules as nutrition.
Question 12.
In Spirogyra, asexual reproduction takes place by:
(a) breaking up filaments into smaller bits.
(b) division of a cell into two cells.
(c) division of a cell into many cells.
(d) formation of young cells from older cells.
Answer:
(a) breaking up of filaments into smaller bits.
Explanation: In Spirogyra, asexual reproduction takes place by fragmentation, i.e., the organism simply breaks up into smaller pieces upon maturation. Each piece grows into a new individual without forming any gametes.
Question 13.
A cylindrical conductor of length T and uniform area of cross-section ‘A’ has resistance ‘R’. The area of cross-section of another conductor of the same material and the same resistance but of length ‘2l’ is :
(a) 0.5 A
(b) 1.5 A
(c) 2 A
(d) 3 A
Answer:
(c) 2 A
Explanation: A cylindrical conductor of length ‘l’ and uniform area of cross-section ‘A’ has resistance ‘R’. The area of cross-section of another conductor of same material and same resistance but of length ‘2l’ will be 2 A. This can be explained as:
Question 14.
Dominant alleles are expressed exclusively in a heterozygote, while recessive traits are expressed only if the organism is ………………… for the recessive allele.
(a) Homozygous
(b) Heterozygous
(c) Normal
(d) None of these
Answer:
(a) Homozygous
Explanation: Mendel’s law of dominance states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. Rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively. The recessive allele will remain “latent,” but will be transmitted to offspring by the same manner in which the dominant allele is transmitted. The recessive trait will only be expressed by offspring that have two copies of this allele.
Question 15.
The figure given below shows the magnetic field produced by a currents carrying wire. Which of the following diagrams shows it correctly?
Answer:
Explanation: As when current flows through and current-carrying wire, then direction of magnetic I field is calculated by right hand thumb rule.
Question 16.
The Ratio of Number of Chromosomes in a Human Zygote and a Human Sperm is:
(a) 2 : 1
(b) 3 : 1
(c) 1 : 2
(d) 1 : 3
Answer:
(a) 2 : 1
Explanation: The number of chromosomes in human sperm is half the number of chromosomes in a zygote i.e., their ratio is 2 : 1.
Question No 17 to 20 consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Question 17.
Assertion: When a current carrying rod is suspended between a U-shaped magnet, and the rod deflects. Reason: A force is exerted on the rod due to the magnetic field.
Answer:
(a) Both A and R are true and R is the correct explanation of A.
Explanation: A force is always exerted due to magnetic field in the same way electric current flowing I through any conductor produces magnetic field. And in this case, Fleming’s left-hand rule is used to I predict the directions of the magnetic field, current and displacement.
Question 18.
Assertion: Mendel selected the pea plant for his experiments.
Reason: Pea plant is cross-pollinating and has unisexual flowers.
Answer:
(c) A is true but R is false.
Explanation: The flowers of pea plants are bisexual and they are self-pollinating, thus, self and cross¬pollination can easily be performed. They have a shorter life span and are the plants that are easier to maintain. Thus, Mendel choose the pea plant.
Question 19.
Assertion: Sometimes, the eye may gradually lose its power of accommodation.
Reason: The crystalline lens of people at old age becomes milky and cloudy.
Answer:
(b) Both A and R are true and R is not the correct explanation of A.
Explanation: The person cannot see the objects distinctly and comfortably because of accommodation. The vision becomes blurred due to the refractive defects of the eye.
Question 20.
Assertion: XX chromosome gives rise to a female child whereas XY gives rise to the male child.
Reason: The Y chromosome in males is smaller than X chromosome.
Answer:
(b) Both A and R are true and R is not the correct explanation of A.
Explanation: The presence of an X chromosome is essential for the development of female characteristics, it is the presence or absence of the Y chromosome that primarily determines the development of male characteristics.
In humans, individuals with two X chromosomes (XX) typically develop as females, while individuals with one X and one Y chromosome (XY) typically develop as males.
The reason provided is not a complete and accurate explanation of why XX chromosomes give rise to female children and XY chromosomes give rise to male children. The sex determination in humans is ! a more intricate process involving the presence or absence of specific genes on the sex chromosomes.
Section – B
Question No. 21 to 26 are very short answer questions.
Question 21.
The refractive indices of kerosene, turpentine and water are 1.44,1.47 and 1.33, respectively. In which of these materials does light travel the fastest?
OR
Why does a ray of light passing through the centre of curvature of a concave mirror gets reflected among the same path after reflection?
Answer:
We know that,
Refractive index = \(\frac{\text { Speed of light in air }}{\text { Speed of light in medium }}\)
So, the speed of light m medium = \(\frac{\text { Speed of light in air }}{\text { Refractive index }}\)
It is obvious from the above relation that the speed of light will be the maximum in that medium which has the lowest refractive index. Now, out of kerosene, turpentine and water, water has the lowest re¬fractive index of 1.33. So, the light will have a maximum speed in the water.
OR
The ray of light passing through the centre of curvature of a concave mirror gets reflected among the same path after a reflection because the angle of incidence is 0°. That is the ray passing through the centre of curvature is incident normally to the mirror. The angle of reflection should also be 0°.
Question 22.
Differentiate between acids and bases.
Answer:
Acids | Bases |
1. Acids are sour in taste. | Bases are bitter in taste. |
2. Acids turn blue litmus to red. | Bases turns red litmus to blue. |
3. An acid is a substance which gives H+ ions in a water solution. | A base is a substance which gives OH– ions in a water solution. |
4. The orange colour of Methyl orange Indicator changes to red in acidic medium. | The orange colour of the Methyl Orange Indicator changes to yellow in bases. |
5. pH value of the acid is less than 7. | pH value of the base is greater than 7. |
6. When non-metallic oxides are dissolved in water, they form acids. SO3 + H2O → H2SO4 |
When metallic oxides are dissolved in water they form bases. CaO + H2O → CO(OH)2 |
Question 23.
Given below is a reaction which occurs in the stratosphere.
O2 \(\rightleftharpoons\) O2 + [O]
(i) Name the two reactions which are in equilibrium thereby maintaining the steady concentration of ozone in the ozonosphere.
(ii) What is being absorbed by the ozone for the occurrence of the above two reactions?
Answer:
(i) Photo-dissociation of ozone and generation of ozone are the two reactions which are in equilibrium thereby maintaining a steady concentration of ozone in the ozonosphere.
(ii) Ultraviolet radiations from the sun are being absorbed by the ozone for the occurrence of given two reactions
Question 24.
State the post-fertilisation changes that lead to fruit formation in plants.
OR
Answer the following questions:
(i) What is translocation? Why is it essential for plants?
(ii) Where do the substances in plants reach as a result of translocation?
Answer:
After fertilization, the zygote divides several times to form an embryo. The fertilized ovule forms a seed. The seed contains an embryo, enclosed in a protective covering, called the seed coat. As the seed grows further, other floral parts wither and fall off. This leads to the growth of the ovary, which enlarges and ripens to become a fruit with a thick wall called the pericarp.
OR
(i) The transport of food from leaves to other parts of the plant is called translocation. Translocation is essential for plants because without it food prepared by the leaves cannot reach other parts of the plant for their growth and development.
(iii) The substances in plants reach other tissues in plants from the leaves because of translocation.
Question 25.
List two different functions performed by the pancreas in our body.
Answer:
Different functions performed by the pancreas in our body are:
- Pancreas makes two hormones i.e., insulin and glycogen that regulates blood sugar level.
- It secretes pancreatic juice that aids in the digestion of food.
Question 26.
Write the structural formulae of all the isomers of hexane.
Answer:
Section – C
Question No. 27 to 33 are short answer questions.
Question 27.
How do Mendel’s experiments show that traits are inherited independently?
Answer:
When Mendel crossed pure pea plants with round, yellow seeds with pure plants with wrinkled, green seeds in F1 generation all pea plants with round and yellow seeds were produced. This shows that round and yellow are dominant characters whereas green and wrinkled are recessive characters. Again, when these F1 plants were crossed round, yellow pea plants, as well as green, wrinkled seeds pea plants were produced. But in addition to these two new characters were produced i.e., round and green, wrinkled and yellow seeds pea plants were produced.
This shows that two pair of characters combines in the F2 generation, but they get separated and behave independently in F2 generation.
Round-yellow, round-green, wrinkled-yellow, wrinkled-green – 9 : 3 : 3 : 1
Question 28.
Three resistors of 2 Ω, 3 Ω and 4 Ω are connected in (i) series, (ii) parallel. Find the equivalent resistance in each case.
Answer:
Given: R1 = 2 Ω, R2 = 3 Ω, R3 = 4 Ω
(i) In series, the equivalent resistance is
Rs = R1 + R2 + R3 = 2 + 3 + 4
= 9 Ω
(ii) In parallel, if the equivalent resistance is Rp, then
\(\frac{1}{\mathrm{R}_{\mathrm{p}}}=\frac{1}{\mathrm{R}_1}+\frac{1}{\mathrm{R}_2}+\frac{1}{\mathrm{R}_3}\)
or \(\frac{1}{\mathrm{R}_{\mathrm{p}}}=\frac{1}{2}+\frac{1}{3}+\frac{1}{4}=\frac{13}{12}\)
or Rp = \(\frac{12}{13}\) = 0.92 Ω
Question 29.
Give reasons for the following:
(i) Platinum, gold and silver are used to make jewellery.
(ii) Sodium, potassium and lithium are stored under oil.
(iii) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Answer:
(i) The reactivity of metals is important in jewelry making. It should be non-reactive to avoid tarnish on the metal. Because electronegativity and nonmetallic character grow from left to right in the periodic table, the oxidizing power of elements increases. Gold, silver and platinum are hence poor oxidizing agents.
They are very lustrous, corrosion-resistant metals. They have strong durability. They may be molded into any shape or pattern due to their extreme malleability and ductility.
Therefore, Platinum, Gold, and Silver are used to make jewelry.
(ii) Sodium, potassium, and lithium are stored in kerosene because they are very reactive metals and react very vigorously with air as well as water. They are kept immersed in kerosene oil in order to prevent their contact with air and moisture.
(iii) Aluminium is a highly reactive metal, but it is resistant to corrosion. The reason for this is that aluminium reacts with oxygen present in the air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. It is light in weight and a good conductor of heat. Therefore, it is used to make utensils for cooking.
Question 30.
What are the characteristics of energy transfer in the biosphere?
Answer:
The characteristics of energy transfer in biosphere are:
1. The ultimate source of energy is the Sun and is converted from one form to another.
2. Energy is continuously transferred the through food chain and energy flow is unidirectional.
3. There is a loss of some energy during transfer from one trophic level to the next.
4. Only 10% of energy is transferred from one trophic level to the next. The solar energy trapped by producers does not revert back to the sun.
5. At each trophic level, some of the energy is utilised by organisms, the rest is lost to the environment and only 10% is available to the next trophic level.
Question 31.
Explain how the following metals are obtained from their compounds by reduction process:
(i) Metal X which is lower in reactivity series.
(ii) Metal Y which is in middle of the reactivity series.
(iii) Metal Z which is high in the reactivity series.
OR
When metal P is treated with a dilute acid Q, then a gas G is evolved which burns readily by making a little explosion.
(i) Name any two metals which can behave like metal P.
(ii) Name any two acids which can behave like acid Q.
(iii) Name the gas G.
(iv) Is the gas G lighter than or heavier than air?
(v) Is the reaction between metal P and dilute acid Q exothermic or endothermic?
Answer:
(i) Metals low in reactivity series are obtained by the method of heating their oxides with carbon.
(ii) Y is in the middle of the series, it can be obtained by heating with a reducing agent like carbon or highly reactive metals like Na, Ca and Al.
(iii) Metal Z is high up in the reactivity series. It can be obtained by electrolytic reduction.
OR
(i) Zinc and Iron.
(ii) Dilute hydrochloric acid and dilute sulphuric acid.
(iii) Hydrogen
(iv) Lighter than air
(v) Exothermic
Question 32.
(i) State a law which determines the direction of the magnetic field around a current-carrying wire.
(ii) Name and state the law which is used to determine the direction of force on a current carrying conductor placed in a magnetic field?
(iii) State condition when the magnitude of force on a current-carrying conductor placed in a magnetic field is (a) zero (b) maximum.
Answer:
(i) Right-hand thumb rule which states that if we hold the current carrying conductor in our right hand such that the thumb points in the direction of flow of current, then the fingers encircle the wire in the direction of the magnetic field.
(ii) The direction of force on a current-carrying conductor placed in a magnetic field is obtained by the Fleming’s left hand rule.
This rule states that ” When forefinger, central finger and thumb of the left hand are stretched in such a way that they are mutually perpendicular to each other, if the forefinger indicates the direction of magnetic field, central finger indicates the direction of the current, then the thumb will indicate the direction of motion of the conductor i.e., the force on the conductor.
(iii) No force acts on a current carrying conductor when the current in conductor is parallel to the magnetic field.
The maximum force is exerted on the current carrying conductor if it is perpendicular to the direction of the magnetic field.
Question 33.
(i) Name the property of baking soda responsible for the following uses:
(a) As an antacid
(b) baking industry
(c) soda-acid fire extinguisher
(ii) There is a unique acid that, unlike other acids, does not release hydrogen gas when it reacts with metals, except for two specific metals. Provide evidence to support this statement.
Answer:
(i) (a) It is alkaline in nature as it neutralises the excess acid produced in our stomach and gives us relief from acidity. So, it is used as an antacid.
(b) Baking soda releases carbon dioxide gas which makes the cake or bread soft and spongy. So, it is used in the baking industry.
(c) Baking soda and sulphuric acid present in soda-acid fire extinguisher reacts to release carbon dioxide gas and this gas is a non-supporter of combustion thus, cutting air supply and the fire gets extinguished.
(ii) Acids like HCl and sulphuric acid react with metals to liberate hydrogen gas.
Zn + 2HCl → ZnCl2 + H2
Mg + H2SO4 → MgSO4 + H2
But nitric acid does not react with metals to liberate hydrogen gas as it is a strong oxidising agent. But magnesium and manganese metal when react with very dilute nitric acid they liberate hydrogen gas.
Zn + 4HNO3 → Zn(NO3)2 + 2H2O + NO2
Mg + 2HNO3 → Mg(NO3)2 + H2
Mn + 2HNO3 → Mn(NO3)2 + H2
Section – D
Question No. 34 to 36 are long answer questions.
Question 34.
(i) What happens when:
(a) Planaria gets cut into two pieces.
(b) A mature Spirogyra filament attains considerable length.
(c) On maturation sporangia bursts.
(ii) Students were asked to observe the permanent slides showing different stages of budding in yeast under the high power microscope.
(a) Which adjustment screw were you asked to move to focus the slides?
(b) Draw diagrams in the correct sequence to show budding in yeast.
(iii) What are the advantages of sexual reproduction over asexual reproduction?
OR
What is placenta? Describe its structure. State its functions in the case of a pregnant human female.
Answer:
(i) (a) Each piece regenerates into a new Planaria.
(b) When a mature Spirogyra filament attains considerable length it breaks into two or more fragments and each fragment grows into a new individual.
(c) On maturation when sporangia bursts, spores are liberated, and they are dispersed. On getting a suitable substratum and under favourable conditions each spore germinates into new mycelium.
(ii) (a) Fine adjustment screws were moved to focus the slides.
(iii) The advantages of sexual reproduction over asexual reproduction are :
1. Variations are produced due to sexual reproduction which helps in better survival of offsprings in the changing environment.
2. More diversity is seen in the case of sexual reproduction as compared to asexual reproduction.
3. Due to recombination and crossing over in the meiosis process during the formation of gametes and as there is a mixing of male and female gametes, genetic variations are seen, which is the main cause of evolution.
OR
Placenta: It is the physical barrier connecting the embryo in the mother’s womb to the uterine wall to allow nutrient uptake, waste removal etc.
Structure: Human placenta is 22 cm in length 2 – 2.5 cm in thickness, and weight 500 g. It has a dark reddish-blue or crimson colour. It is discoidal in shape.
Functions: This provides a large surface area for glucose and oxygen to pass from the mother to the embryo, and the developing efnbryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta. Thus, it provides nourishment to the embryo, helps in excretion and provides immunity to the foetus.
Question 35.
(i) 2 g of ferrous sulphate crystals are heated in a dry boiling tube. Answer the following:
(a) List any two observations.
(b) Name the type of chemical reaction taking place.
(c) Write the chemical equation of the reaction.
(ii) (a) What happens when an aqueous sodium sulphate reacts with an aqueous solution of barium
chloride? State the physical conditions of reactants in which reaction between them will not occurs. Write the chemical equation to show the reaction and what is the type of reaction?
(b) What happens if iron nails are placed in copper sulphate solution for half an hour?
OR
State the following:
(i) pH value of sodium chloride?
(ii) When a solution is added to a cloth strip treated with onion extract, then the smell of onion cannot be detected. State whether the given solution contains an acid or a base.
(iii) One animal and one plant whose stings contain formic acid (or methanoic acid).
(iv) How is the concentration of hydronium ions affected when a solution of an acid is diluted?
(v) What is the common name of water soluble bases?
Answer:
(i) (a) Two observations are:
- Green colour ferrous sulphate crystals will first turn into a dirty white solid and then into a brown residue.
- A gas is evolved with a pungent, suffocating smell.
(b) It is a thermal decomposition reaction.
(c) 2FeSO4 \(\rightleftharpoons\) Fe2O3 + SO2 + SO3.
(ii) (a) When an aqueous solution of sodium sulphate reacts with an aqueous solution of barium
chloride, the product formed is barium sulphate i.e., a white precipitate. The reaction will not take place if the reactants are in a solid state. It is a double displacement type of reaction.
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
(b) When iron nails are placed in copper sulphate solution for half an hour, iron sulphate solution and copper metal is formed.
CuSO4(aq) + Fe(s) → FeS04(aq) + Cu(s)
This reaction occurs because iron is more reactive than copper. Also, a brown substance will be deposited on the iron nails. The deposited substance is nothing but copper.
OR
(a) 7
(b) Base
(c) Animal that contains formic acid- ant. Plant that contains formic acid-nettle plant.
(d)The concentration of hydronium ion decreases.
(e) Alkalis
Question 36.
Myopia occurs when the eyeball becomes longer and the eye lens focuses light too close to the front of the eye. This happens because the distance between the lens and the retina increases. When the distance becomes more than the focal length of the lens, the eye lens cannot form a sharp image of the distant object on the retina but forms an image in front of it as shown in the figure.
If the focal length of the eye lens is short, it will form a sharp image of the distant object in front of the retina and not over it.
(i) Is the eye lens made of glass?
(ii) A myopic person uses specs of power – 0.2 D, what is the distance of the far point of his eye?
(iii) Which lens is used for correcting a myopic eye?
(a) Convex lens
(b) Concave lens
(c) Bifocal lens
(d) None of the above
(iv) The human eye forms the image of an object at its:
(a) Cornea
(b) Pupil
(c) Iris
(d) Retina
OR
Answer the following questions:
(i) What is persistence of vision?
(ii) Define the term angle of deviation.
(iii) Define the term power of accommodation. Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly?
Answer:
(i) No, the eye lens is not made of glass, it is made of fibrous jelly like material.
(ii) We know,
P = – 0.2 D
f = \(\frac{1}{P}=\frac{1}{-0.2}\) = -5 m
Distance of far point of his eye is 5 m.
(iii) (b) Concave lens
(iv) (d) Retina
OR
(i) The image of any object formed on the retina persists for about 1/16 of a second. This continuance of sensation of eye for sometime even after the removal of the object is called persistence of vision.
(ii) The angle between the incident ray produced forward and the emergent ray produced backward is called angle of deviation.
(iii) The ability of the eye lens to adjust its focal length, is called the power of accommodation. There should be a contraction of ciliary muscles, that will increase the curvature of the eye lens and becomes thicker, so the focal length of the eye lens will decrease. It will thus enable us to see the objects clearly.
Section – E
Question No. 37 to 39 are case – based/data -based questions with 2 to 3 short sub – parts. Internal choice is provided in one of these sub-parts.
Question 37.
Most human chromosomes have a copy from the mother and a copy from the father, making 22 pairs. However, there is one pair called the sex chromosomes that is different. In women, both sex chromosomes ate the same and are called X. In men, one sex chromosome is a normal-sized X, while the other is a shorter one called Y. This is why women are XX and men are XY. As shown in the diagram, half of the children will be boys, and half will be girls. Regardless of whether they are boys or girls, all children inherit an X chromosome from their mother. The sex of the children is determined by what they inherit from their father. If a child inherits an X chromosome from the father, they will be a girl; if they inherit a Y chromosome, they will be a boy.
(a) Who determines the sex of a child; mother or father?
(b) What will be the gender of a child if it inherits Y chromosome from father?
OR
How many pairs of chromosomes are present in humans?
Answer:
(a) Father determines the sex of a child.
It is therefore thought that genes for femaleness is associated with the X chromosomes and genes for maleness are on Y chromosomes. Hence, the presence of the Y chromosome is a must for the determination of sex of the male person. When fertilisation takes place between a sperm carrying the X chromosome and an egg cell with the X chromosome; then, the developed zygote will contain an XX combination, the child will be a girl. If a sperm carrying Y chromosome unites with an egg cell containing the X chromosome then the zygote will carry XY chromosome and the child will be a boy.
Hence, it can be concluded that the sex of the baby is depended on the father.
(b) The child will be boy (Male)
OR
23 pairs out of which twenty-two of these pairs, are called autosomes, they look the same in both males and females. One pair called sex chromosomes are different in both male and female.
Question 38.
1. Take three iron nails and clean them by rubbing them with sand paper.
2. Take two test tubes marked (A) and (B). In each test tube, take about 10 mL of copper sulphate solution.
3. Tie two iron nails with a thread and immerse them carefully in the copper sulphate solution in test tube B for about 20 minutes.
4. Keep one iron nail aside for comparison.
5. After 20 minutes, take out the iron nails from the copper sulphate solution.
6. Compare the intensity of the blue colour of copper sulphate solutions in test tubes.
(a) What is shown in the above activity?
(b) The iron nail becomes brownish in colour and the blue colour of the copper sulphate solution fades? Why?
(c) Is the reaction possible? Give reason.
Cu(s) + ZnSO4(aq) → CuSO4(aq) + Zn(s)
OR
Give any two examples of a Displacement reaction.
Answer:
(a) The above activity shows Displacement reaction.
(b) The reason for this can be understood with the help of the following reaction,
In this reaction, iron has displaced or removed another element, copper, from the copper sulphate solution. Therefore, the iron nail becomes brownish in colour and the blue colour of copper sulphate solution fades.
(c) Zinc is more reactive element than copper. Therefore, copper cannot displace zinc from its solution. Hence, the given reaction is not possible.
OR
Question 39.
In our homes, we receive the supply of electric power through a main supply (also called mains), either supported through overhead electric poles or by underground cables. One of the wires in this supply, usually with red insulation cover, is called live wire (or positive). Another wire, with black insulation, is called neutral wire (or negative). In our country, the potential difference between the two is 220 V. At the meter-board in the house, these wires pass into an electricity meter through a main fuse. Through the main switch. They are connected to the line wires in the house. These wires supply electricity to separate circuits within the house. Often, two separate circuits are used, one of 15 A current ratings for appliances with higher power ratings such as geysers, air coolers, etc. The other circuit is of 5 A current rating for bulbs, fans, etc. The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house. This is used as a safety measure, especially for appliances with a metallic body, for example, electric press, toaster, table fan, refrigerator, etc. The metallic body is connected to the earth wire, which provides a low-resistance conducting path for the current. Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.
(a) What is the potential difference between red wire and black wire?
(b) Why are two separate circuits used in homes?
(c) How is earth wire connected in homes?
OR
(d) How does earth wire act as a safety device?
Answer:
(a) 220 V
(b) Two separate circuits are used, one of 15 A current ratings for appliances with higher power ratings such as geysers, air coolers, etc. The other circuit is of 5 A current rating for bulbs, fans, etc.
(c) The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house.
OR
(d) It is used as a safety measure, especially for appliances with a metallic body, for example, electric press, toaster, table fan, refrigerator, etc. The metallic body is connected to the earth wire, which provides a low-resistance conducting path for the current. Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.