Science 31/3/3 2018-2019 English Medium Class 10 Question Paper Solution

Define 1 kilowatt hour. 

Generally, we do not clean natural ponds or lakes but an aquarium needs periodic cleaning. Why? 

List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision. 

Show the formation of Na2O by the transfer of electrons. 

List in tabular form two differences between reflex action and walking. 

List in tabular form two differences between pepsin and trypsin. 

Name the process used to harness nuclear energy these days. Explain it briefly. List two advantages of using nuclear energy in place of fossil fuels. 

Why are forests considered “biodiversity hot spots”? Suggest four approaches towards the conservation of forests. 

What is atmospheric reflection? Explain with the help of a labelled diagram that the position of a star as seen by us is not its true position. 

When do we consider a student sitting in the class to be myopic? List two causes of this defect. Explain using a ray diagram how this defect of eye can be corrected.

Write the chemical formula of washing soda. How can it be obtained from baking soda? List two industries in which washing soda is used for other purposes than washing clothes. 

Out of three metals P, Q and R, P is less reactive than Q and R is more reactive than P and Q both. Suggest an activity to arragne P, Q and R in order of their decreasing reactivity. 

Name the ore of mercury. With the help of balanced chemical equations, explain the process of extraction of mercury from its ore.

(a) How is possible valency of an element determined from the electronic configuration of its atom ?

(b) Determine the valency of an element X whose atomic number is 15. 

What is haemoglobin? State the consequences of deficiency of haemoglobin in our bodies. 

 Explain the following :

(a) Speciation

(b) Natural Selection 

Mendel, in one of his experiments with pea plants, crossed a variety of pea plant having round seeds with one having wrinkled seeds. State Mendel’s observations giving reasons of F₁ and F₂ progeny of this cross. Also, list any two contrasting characters, other than round seeds of pea plants that Mendel used in his experiments.

Explain the ways in which glucose is broken down in absence or shortage of oxygen. 

List in tabular form three distinguishing features between cerebrum and cerebellum.

What is hydrocarbon? Give its one example. 

Give the structural difference between saturated and unsaturated hydrocarbons with two examples each.

Name of the following compounds : 

(a) What is double displacement reaction? Explain with an example.

(b) A small amount of quick lime is added to water in a beaker.

     (i) Name and define the type of reaction that has taken place.

    (ii) Write balanced chemical equation for the above reaction and the chemical name of the product formed.

    (iii) List two main observations of this reaction. 

(a) Design an activity to demonstrate the decomposition reaction of lead nitrate.

(b) Draw labelled diagram of the experimental set-up. List two main observations.

(c) Write balanced chemical equation for the reaction stating the physical state of the reactant and the products.

List four characteristics of the image formed by a concave lens of focal length 20 cm when the object is placed at a distance of 40 cm from its optical centre. 

The size of image of an object by a convex lens of focal length 20 cm is observed to be reduced to  `1/3` rd of its size . Find the distance of the object from the optical centre of the lens . 

Three resistors of resistances R₁ , R₂ and R₃  are connected (i) in series, and (ii) in parallel. Write expressions for the equivalent resistance of the combination in each case. 

Two identical resistros of  `12 Omega` each are connected to a battery of 3V . Calculate the ratio of the power consumed by the resulting combinations with minimum resistance and maximum resistance.

Write the relation between resistance and electrical resistivity of the material of a conductor in the shape of a cylinder of length `'l'`  and area of cross-section `'A'` . Hence derive the S.I. unit of electrical resistivity.

Resistance of a metal wire of length 5 m is 100 Ω . If the area of cross - section of the wire is `3 × 10^-7  "m"^2` , Calculate the resistivity of the metal . 

Name and state the rule of determine the direction of force experienced by a current carrying straight conductor placed in a uniform magnetic field which is perpendicular to it. 

Draw a labelled diagram of an electric motor.

What is reproduction? List its two types. 

How are the modes for reproduction different in unicellular and multicellular organisms?

What are Sexually Transitted Diseases (STD)? List two viral and two bacterial STDs. 

What is contraception ? List three reasons for adopting contraceptive methods. 

In the expriment of preparing a temporary mount of a leaf peel to observe stomata, we use two liquids other than water. Name these two liquids and state when and why these liquids are used. 

List four precautions in proper sequence which we observe while preparing a temporary mount of a leaf peel. 

A student has set up "CO₂ is released during respiration”. After about 1 hour he observes no change in the water level in the delivery tube. Write two possible resons for the failure of the experiment. 

Consider the sacle of voltmeter shown in the diagram and answer the following questions : 

(a) What is the least count of the voltmeter?

(b) What is the reading shown by the voltmeter ?

(c) If the voltmeter is connected across a resistor of 20 `Omega` how much current is flowing through the resistor?

List in proper sequence the steps of the experiment for determining the approximate focal length of a given concave mirror by obtaining the image of a distant object.

A student has to trace the path of a ray of light passing through a rectangular glass slab for four different values of angle of incidence.

(a) Write two important precautions for this experiment.

(b) List two conclusions the student will draw based on his experiment. 

List the conclusions you will draw while studying the following properties of ethanoic acid : 

(a) Odour

(b) Solubility in water

(c) Effect on litmus paper

(d) Reaction with sodium hydrogen carbonate 

What is observed after about 1 hour of adding the strips of copper and aluminium separately to the ferrous sulphate solution filled in two beakers? Name the reaction if any change in colour is noticed. Also, write a chemical equation for the reaction.

A student wants to study a decomposition reaction by taking ferrous sulphate crystals. Write two precautions he must observe while performing the experiment.