CBSE Sample Papers for Class 10 Science Paper 7
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 7.
Time Allowed: 3 hours
Max. Marks: 80
- 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.
Why do we feel tired and have pain in muscles and sometimes get cramps after strenuous physical work?
What will happen if intake of iodine in our diet is low?
“Elements in Periodic Table show periodicity of properties”. List any four such properties.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
How are coal and petroleum formed? Name two elements present in coal and petroleum in addition to carbon.
Complete the missing components/variables given as x and y in the following reactions:
- Pb(NO3)2(aq) + 2KI(aq) → PbI2(x) + 2KNO3V)
- Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + x(s)
- Zn(s) + H2SO4(aq) → ZnSO4(x) + H2(y)
- CaCO3(s) CaO(s) + CO2(g)
Translate the following statements into chemical equations and then balance the equations:
- Phosphorus burns in oxygen to give phosphorus pentoxide.
- Aluminium metal replaces iron from ferric oxide, Fe2O3, giving aluminium oxide and iron.
- Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
- Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
- State one example each of a synthetic indicator and olfactory indicator.
- How do bacteria decay our teeth? Why do we use basic tooth pastes for cleaning our teeth?
Döbereiner arranged the elements in the order of increasing atomic masses in a triad. The arrangement was modified by John Newlands and later by Dimitri Mendeléev. Even Mendeléev’s arrangement was later modified by Henry Moseley resulting in the Modern Periodic Table. There are many other similar examples in the history of scientific advancement where theories and novels were modified by later scientists and the original contributors accepted these modifications happily.
Answer the following questions based on the above information:
- How does the Modern Periodic Law given by Moseley different from Periodic Law stated by Mendeléev?
- What scientific values can be associated with the above anecdotes?
- Give an example from your life experiences so far that reflects display of such values by you.
What will happen if:
- Mucus is not secreted by the gastric gland.
- Leaves of plants are covered with vaseline.
- Bile is not produced in liver.
- How do organisms reproduce by fission? Write names of any two organisms which reproduce by this method.
- Differentiate between the fission of Leishmania and Plasmodium.
- What is DNA?
- What is clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
The sex of the baby is determined by the father. Justify. Give an example where sex determination is regulated by environmental factors.
- Differentiate between dominant and recessive traits.
- ‘Genes control traits’ Explain this statement with an example.
A student has focused the image of a candle flame on a white screen using a concave mirror. The situation is as given below: Length of the flame = 1.5 cm Focal length of the mirror = 12 cm Distance of flame from the mirror = 18 cm If the flame is perpendicular to the principal axis of the mirror, then calculate the following:
- Distance of the image from the mirror
- Length of the image
If the distance between the mirror and the flame is reduced to 10 cm, then what would be observed on the screen? Draw ray diagram to justify your answer for this situation.
The potential difference between the terminals of an electric heater is 110 V, when it draws a current of 5A from the source. What current will the heater draw and what will be its wattage if the potential difference is increased to 220V. Consider that the resistance of the heater element does not change with temperature.
Two wires made of copper and nichrome have equal lengths and equal resistance. Which is thicker? The resistivity of nichrome is greater than resistivity of copper. Why are alloys commonly used in electrical heating devices such as electric toasters, electric iron, etc.?
A coil made of insulated copper wire is connected to a galvanometer. What will happen to the deflection of the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from it? Give reason for your answer and name the phenomenon involved.
- Why do metals high up in the reactivity series not reduced by heating with carbon? What is the reduction process used for sodium chloride?
- A metal is slowly eaten away in the presence of air and water. To avoid this, it is mixed with carbon (0.05%) or nickel and chromium.
- Identify the metal.
- What is the substance formed on mixing carbon?
- State another methods that can be used to protect the metal.
- Complete the following equations:
- Write the name of the next homologue of CH3OH and HCOOH.
- How does boiling point and melting point of hydrocarbons change with increase in molecular mass?
- Define homologous series of organic compounds. Mention any two characteristics of homologous series.
- Describe a chemical test to distinguish between ethanol and ethanoic acid.
- Identify functional group in pentanone.
- An endocrine gland P is located below the stomach in the human body. The gland P secrets a hormone H. The deficiency of hormone H in the body leads to rise in blood sugar due to which a disease D is caused.
- Name the gland P and the hormone H.
- State the function of hormone H.
- Name the disease D.
- Suggest two precautions to be taken by the person who is suffering from the disease D.
- Which part of the human brain is:
- the main thinking part of the brain?
- responsible for maintaining the posture and balance of the body?
- What is meant by power of accommodation of eye? A person with a defective vision cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision? Draw a diagram of this corrected eye.
- A person having presbyopia uses a bifocal lens to restore proper vision. Which part of this lens is convex and which part is concave?
- Name the part of the eye where image is formed by the lens. What is the nature of the image formed? How is this image sent to the brain?
- Why do different colours get separated when white light passes through prism? How can we recombine the components of white light after a prism has separated them? Explain with the help of figure.
- List the factors on which scattering of light depends.
- What is Tyndall effect?
- With the help of an activity, explain the method of inducing electric current in a coil with a moving magnet. State the rule used to find the direction of electric current thus generated in the coil.
- Two circular coils P and Q are kept close to each other, of which coil P carries a current. What will you observe in Q?
- If current in the coil P is changed.
- If both the coils are moved in the same direction with the same speed? Give reason.
Give reason to justify the following:
- The existence of decomposers is essential in a biosphere.
- Flow of energy in a food chain is unidirectional.
When a student added zinc granules to dilute HCl, a colourless and odourless gas was evolved, which was then tested with a burning matchstick; what would be observed?
A student is studying the properties of acetic acid. List two physical properties of acetic acid he observes. What happens when he adds a pinch of sodium hydrogen carbonate to this acid? Write any two observations.
When soap is added to hard water, it reacts with the salts to form a scum. Why does this scum form?
Why safranin and glycerine are used to prepare a temporary mount of a leaf peel?
Mention the observations of budding in yeast.
The diagram shows radiation from a lamp passing through a prism. Which type of radiations are found at P and Q?
Find the voltmeter readings for the circuits A and B shown below.
This is due to accumulation of lactic acid in the muscles.
- When iodine intake is low, release of thyroxine from thyroid gland will be less by which protein, carbohydrate and fat metabolisms will be affected.
- A person might suffer from goitre in case of iodine deficiency in the body.
- Atomic size
- Valency or combining capacity
- Metallic property
- Non-metallic property.
Given, u = -10 cm, ƒ = + 15 cm, v = ?
That is image is formed at a distance of 6 cm from the mirror behind it. The image is erect and virtual.
Coal and petroleum are formed from the degradation of biomass, millions of years ago.
Other elements that are present are
- oxygen. (Any two)
- x — (s); y — (aq)
- x — 2Ag
- x — (aq); y — (g) :
- x — Heat
- P4 + 5O2 → 2P2O5
- Fe2O3(s) + 2Al(s) → Al2O3(s) + Fe(s)
- CS2 + 3O2 → 2SO2 + CO2
- BaCl2 + ZnSO4 → BaSO4 + ZnCl2
- Synthetic indicator – methyl orange Olfactory indicator – onion or vanilla essence
- Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. These acids reduce pH of the mouth. Tooth decay starts when the pH of mouth is lower than 5.5. Toothpastes are generally basic hence they neutralise the excess acid and prevent tooth decay.
- Mendeléev’s Periodic Law states that the properties of elements are the periodic function of their atomic masses. Mosley’s Modern Periodic Law states that the properties of elements are the periodic function of their atomic numbers.
- Open-mindedness, ability to accept failure, intellectual, honesty, respect for other’s views, spirit of enquiry.
- Acceptance of wrong traditional beliefs initially and change in these beliefs at a later stage.
- When mucus is not secreted by the gastric gland, inner lining of stomach may get damaged by the action of HCl acid.
- Plant when covered with vaseline will not be able to perform following:
- Photosynthesis as CO2 may not enter.
- Respire as exchange of gases (02) and CO2) may not occur. –
- Transpiration (Any one)
- Emulsification of fat will not take place when bile is not produced in liver which will effect the digestion of fat.
- During fission, cell division takes place which leads to creation of new individuals. Example: bacteria, protozoa
- In Leishmania, binary fission occurs in a definite orientation whereas Plasmodium undergoes multiple fission.
- DNA or deoxyribonucleic acid, is the hereditary material present in the cell in all organisms. It is responsible for all the characteristics exhibited by the organism.
- Clone is the identical copy of an organism. In asexual reproduction only one parent is involved. So, the offsprings acquire characteristics from one parent and no variation is introduced. Therefore, offsprings exhibit similarities.
The sex of the human individual is genetically determined. Human female have a pair of X chromosomes while human males have one X and one Y chromosome in their cells. Females produce one type of ova whereas males produce two types of sperms-X type and Y type. When X type sperm meets with the ovum, a female child is born and when a Y type sperm meets with an ovum a male child is born. Thus half the children will be boys and half will be girls. Thus the sex of the children is determined by what they inherit from their father. In snails, sex is determined by environmental factors, i.e., temperature.
- The trait that appears in the progenies when breeds of different traits are crossed are called dominant traits. It appears in more numbers. The trait which though appears in progenies but is not so conspicuous is called recessive trait. These are less in numbers.
- Consider tallness as a characteristic. Plant height depends on particular plant hormone which in turn will depend on the efficiency of the process for making it. If the enzyme responsible for the production of this hormone is efficient, plant will be tall. If the gene for that enzyme has an alteration that makes enzyme less efficient, the amount of hormone will be less and thus plant will be short.
Given: height of object, h = + 1.5 cm; focal length, f = – 12 cm; object distance, u = – 18 cm; image distance, v = ?; height of image, h’ = ?
(i) Applying mirror formula,
= – 3 cm (Magnified, inverted image)
If u = – 10 cm, no distinct image would be formed on the screen. In this case the image formed will be virtual.
Potential difference V = 110 V,
When potential difference is increased to 220 V, the current is
∴ Wattage of the heater, P = V × I = 220 V × 10 A = 2200 W
For copper wire, Rc = …(i)
For nichrome wire, RN = …(ii)
From (i) and (ii),
[∵ esistances are equal]
since, ρN > ρc ∴ AN > Ac
Thickness of nichrome is greater. Since resistivities of alloys are higher and also they do not oxidise (burn) readily at higher temperature, they are commonly used in electrical heating devices.
When coil is moved towards a stationary magnet, the magnetic field associated with the coil will change and so current will be induced in the coil. This causes galvanometer to show deflection in one direction. Now when coil is moved away, the magnetic field will decrease and so current induces in the opposite direction causing galvanometer to show deflection in opposite direction. The phenomenon is electromagnetic induction.
- Metals high up in the reactivity series have more affinity for oxygen than
carbon so they are not reduced by heating with carbon.
The reduction process used for NaCl is electrolysis of molten NaCl.
- Metal is iron (Fe).
- On mixing carbon and iron, stainless steel is formed.
2. Next homologues are ethanol and ethanoic acid.
3. With increase in molecular mass, boiling point and melting point of hydrocarbons increases.
- A homologous series is a group of organic compounds having same functional group and similar chemical properties in which the successive compounds differ by CH2 group. Characteristics
- All the members of a homologous series have similar chemical properties.
- There is a gradation in physical properties.
- On adding solid NaHCO3, an effervescence occurs with the evolution of CO2 in case of ethanoic acid while ethanol does not show any action.
- Ketone is the functional group.
- Gland P is pancreas and the hormone H is insulin.
- Hormone H, i.e., insulin controls the blood sugar.
- Disease D is Diabetes.
- Precaution should be taken by the diabetic person by controlling sugar in the blood through:
- Controlling diet – Doing regular physical exercise or walking
- Taking regular medicine as advised by the doctor.
- Reducing weight (Any two)
- Forebrain is the main thinking part of the brain.
- Cerebellum (hind brain) maintains the posture and balance of the body.
- The ability of the eye to focus both near and distant objects, by adjusting its focal length is called the accommodation of the eye. Corrective lens that should be used is concave lens.
- For bifocal lens, upper part of the lens is concave lens and lower part of the lens is convex lens.
- Image is formed by the eye lens on retina. Image formed is real. Retina has light sensitive cells which get retinated upon illumination and generate electrical signals which are sent to brain via optic nerve.
- A spectrum is the band of distinct colours we obtain when the white light is split by a prism. We can recombine the component of white light by passing them through a prism placed upside down Recombination near the given prism. When we pass white light through two Dispersion identical prism held side by side with their refracting edges in Q First prism opposite directions; the first prism disperses white light but the second prism recombines the components of white light. Thus light emerging from second prism is white.
- Scattering of light depends upon the size of particles and the wavelength of light.
- The phenomenon of scattering of light by the colloidal particles give rise to Tyndall effect.
- Take a coil of wire ABA having a large number of turns.
- Connect the ends of the coil to a galvanometer.
- Take a strong bar magnet and move its north pole towards the end B of the coil.
- There is a momentary deflection in the needle of the galvanometer, say to the right. This indicates the presence of a current in the coil AB. The deflection becomes zero the moment the motion of the magnet stops.
- Now withdraw the north pole of the magnet away from the coil. Now the galvanometer is deflected toward the left, showing that the current is now set up in the direction opposite to the first.
- Place the magnet stationary at a point near to the coil, keeping its north pole towards the end B of the coil. We see that the galvanometer needle deflects toward the right when the coil is moved towards the north pole of the magnet. Similarly, the needle moves toward left when the coil is moved away. When the coil is kept stationary with respect to the magnet, the deflection of the galvanometer drops to zero. To find the direction of electric current Fleming’s right hand rule is applied. According to it, if we stretch the forefinger, middle finger and thumb of our right hand mutually perpendicular in such a way that thumb points along the direction of motion of conductor, forefinger along the direction of magnetic field; then the middle finger points along the direction of induced current.
- When current in P is changed, the field associated with Q will vary causing an induced current in Q.
- If both the coils are moved in the same direction with same speed, there will not be any change in the field associated with Q. Hence no current will be induced in Q.
- The existence of decomposers is essential in a biosphere because they breakdown complex organic substances into simple inorganic substances that can be absorbed by the plants. Thus, decomposers:
- replenish the soil naturally.
- helps in removing the biodegradable waste.
- In a food chain the energy moves progressively through the various trophic levels, it is no longer available to the previous level (i.e., autotrophs) and the energy captured by the autotrophs does not go back to the solar input. Hence, the flow of energy is unidirectional.
When the colourless gas was tested with a burning matchstick, the matchstick extinguished and the gas burnt with a pop sound. This is because when zinc granules are added to dilute HCl, hydrogen gas is evolved.
Physical properties of acetic acid observed are:
- Acetic acid is a colourless liquid.
- It is miscible or soluble in water. On adding a pinch of sodium hydrogen carbonate,
- brisk effervescence is observed.
- there is evolution of a colourless and odourless gas.
This scum forms due to the formation of calcium and magnesium salts of fatty acid which is formed when calcium and magnesium ions of hard water react with soap
This is because safranin stains the leaf structures and helps in obtaining clear vision of these in microscope. Glycerine keeps these structures away from drving up.
Budding in yeast:
- A small outgrowth or protuberance is seen on the parent cell.
- Nucleus divides and is later seen in the bud.
- Repeated budding forms a chain of cells.
Infra-red is found at P and ultraviolet is found at Q.
Only circuit B, with a dot within the symbol of the plug key, is a closed circuit in which current is flowing and will show non-zero voltage. The voltmeter reading, for the set ups shown, would be (nearly) equal to the voltage of the battery.
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