Science 31/4/2 2018-2019 English Medium Class 10 Question Paper Solution

Define current. Give its S.I. unit.

Name the component of sunlight which facilitates drying of wheat after harvesting.

State the laws of refraction of light.

List four characteristics of the image formed by a concave mirror of focal length 40 cm when the object is placed in front of it at a distance of 20 cm from its pole.

Draw magnetic field lines in and around a current-carrying straight solenoid.

Write the name and molecular formula of a carbon compound having its name suffixed with "-ol" and having two carbon atoms in its molecule. With the help of a chemical equation indicate what happens when this compound is heated with excess conc. H₂SO₄.

Define the term evolution. "Evolution cannot be equated with progress." Give examples to justify this statement.

Plants do not have any nervous system but yet, if we touch a sensitive plant, some observable changes take place in its leaves. Explain how could this plant respond to the external stimuli and how it is communicated.

Name the hormone that needs to be administered to increase the height of a dwarf plant.

Name the hormone that needs to be administered to cause rapid cell division in fruits and seeds.

Write the function of the following in the human alimentary canal:

Saliva

Write the function of the following in the human alimentary canal:

HCl in stomach

Write the function of the following in the human alimentary canal:

Bile juice

Write the function of the following in the human alimentary canal:

Villi

Write one function each of the following enzymes:

Pepsin

Write one function each of the following enzymes:

Lipase

Salt 'P', commonly used in bakery products, on heating gets converted into another salt 'Q' which itself is used for the removal of hardness of water and a gas 'R' is evolved. The gas 'R', when passed through freshly prepared lime water, turns milky. Identify 'P', 'Q' and 'R', giving a chemical equation for the justification of your answer.

Classify the following reaction into different type:

AgNO₃(aq) + NaCl(aq) →AgCl(s) + NaNO₃(aq)

Classify the following reaction into different type:

CaO(s) + H₂O(l) → Ca(OH)₂(aq)

Classify the following reaction into different type:

\[\ce{2KClO3(s)->[\Delta] 2KCl(aq) + 3O2(g)}\]

Classify the following reaction into different type:

Zn + CuSO₄ → ZnSO₄ + Cu

Translate the following statement into chemical equation and then balance it.

Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

What is the colour of this precipitate? Name the compound precipitated.

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

Write the balanced chemical equation for this reaction.

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

List two types of reactions in which this reaction can be placed.

How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle? Why can the same process not be applied for them? Name the process used for the extraction of these metals.

The following diagram shows two parallel straight conductors carrying the same current. Copy the diagram and draw the pattern of the magnetic field lines around them showing their directions. What is the magnitude of the magnetic field at a point 'X' which is equidistant from the conductors? Give justification for your answer.

What is the cause of the dispersion of white light through a glass prism? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prisms.

What is meant by scattering of light? Use this phenomenon to explain why the clear sky appears blue or the Sun appears reddish at sunrise.

Natural water bodies are not regularly cleaned whereas an aquarium needs regular cleaning. Why?

What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.

How is ozone formed in the upper atmosphere? State its importance. What is responsible for its depletion? Write one harmful effect of ozone depletion.

What is the exploitation of resources with short term aims? List its four advantages.

If we pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F₁ generation. If we now self-cross the pea plant of F₁ generation, then we obtain pea plants of F₂ generation.

(a) What do the plants of F₂ generation look like?

(b) State the ratio of tall plants to dwarf plants in F₂ generation.

(c) State the type of plants not found in F₁ generation but appeared in F₂ generation, mentioning the reason for the same.

Answer the following question:
What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor? Justify your answer.

Define vegetative propagation. List its two methods.

Why is this mode practiced for growing some types of plants?

Draw labelled diagrams to illustrate budding in Hydra.

What is contraception? List four different methods. State four reasons for adopting contraceptive methods.

List two limitations of Newlands' Law of Octaves.

Write the electronic configuration of two elements A and B whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element A reacts with element B. State whether this compound is acidic, basic or neutral. Give a reason to justify your answer.

Distinguish between esterification and saponification reactions with the help of chemical equations for each.

With a labelled diagram describe in brief an activity to show the formation of ester.

What is the difference between soaps and detergents? State, in brief, the cleansing action of soaps in removing an oily spot from a fabric. Why are soaps not very effective when a fabric is washed in hard water? How is this problem resolved?

Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.

Two electric bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to electric mains of 220 V. Find the current drawn by the bulbs from the mains.

How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistors R₁, R₂ and R₃ in series connected to a battery of V volts?

Study the following circuit and find out:
      (i) Current in 12 Ω resistor.
      (ii) The difference in the readings of A₁ and A₂, if any.

A person is unable to see objects distinctly placed within 50 cm from his eyes.

(a) Name the defect of vision the person is suffering from and list its two possible causes.

(b) Draw a ray diagram to show the defect in the above case.

(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.

(d) Draw a labeled diagram for the correction of the defect in the above case.

Which one of the following is the correct set-up for studying the dependence of the current on the potential difference across a resistor and why?

Study the following ray diagram and list two mistakes committed by the student while tracing it. Rectify these mistakes by drawing the correct ray diagram to show the real position and size of the image corresponding to the position of the object AB.

A student has to trace the path of a ray of light through a glass prism. List four precautions he should observe for better results.

List two observations on the basis of which it may be concluded that the given slide shows binary fission in Amoeba.

Write four sequential steps of the procedure of the experiment "Preparing a temporary mount of a leaf peel to show stomata".

In the experimental set-up to show that "the germinating seeds give out carbon dioxide", answer the following questions:
(i) Why do we keep the conical flask airtight?
(ii) Name the substance kept in the small test tube inside the conical flask. Write its role.
(iii) Why does water rise in the delivery tube?

A student mixes sodium sulphate powder in barium chloride powder. What change would the student observe on mixing the two powders? Justify your answer and explain how he can obtain the desired change.

Arrange the following metals in the increasing order of their reactivities:

Copper, Zinc, Aluminium, and Iron

List two observations you would record in your notebook 30 minutes after adding iron filings to copper sulphate solution.

A solution 'X' gives orange colour when a drop of it falls on pH paper, while another solution 'Y' gives bluish colour when a drop of it falls on pH paper. What is the nature of both solutions? Determine the pH of solutions 'X' and 'Y'.