Science Foreign Set 3 2014-2015 English Medium Class 10 Question Paper Solution

Write the name and molecular formula of the first member of the homologous series of alkynes.

What is DNA?

List two natural ecosystems.

What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.

Write two advantages of sustainable management of natural resources. Out of the two − reuse and recycle − which is better and why ?

List four advantages of conserving water in the form of ground water.

Write the name and structural formula of the compound obtained when ethanol is heated at 443 K with excess of conc. H₂SO₄. Also write chemical equation for the reaction stating the role of conc. H₂SO₄ in it.

What is meant by functional group in carbon compounds? Write in tabular form the structural formula and the functional group present in the following compounds:
(i) Ethanol
(ii) Ethanoic acid

Four elements P, Q, R and S belong to the third period of the Modern Periodic Table and have respectively 1, 3, 5 and 7 electrons in their outermost shells. Write the electronic configurations of Q and R and determine their valences. Write the molecular formula of the compound formed when P and S combine.

In the following table, the positions of six elements A, B, C, D, E and F are given as they are in the Modern Periodic Table :

	1	2	3-12	13	14	15	16	17	18
2	A			B		C			D
3					E				F

On the basis of the above table, answer the following questions :
(i) Name the element which forms only covalent compounds.
(ii) Name the element which is a metal with valency three.
(iii) Name the element which is a non-metal with valency three.
(iv) Out of B and C, whose atomic radius is bigger and why ?
(v) Write the common name for the family to which the elements D and F belong.

Draw a diagram of the longitudinal section of a flower exhibiting germination of pollen on stigma and label (i) ovary, (ii) male germ-cell, (iii) female germ-cell and (iv) ovule on it.

List two advantages of vegetative propagation.

 What is placenta? What is its function?

"It is possible that a trait is inherited but may not be expressed." Give a suitable example to justify this statement.

"The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it". Draw a flow chart showing determination of sex of a newborn to justify this statement.

A student wants to project the image of a candle flame on a screen 80 cm in front of a mirror by keeping the candle flame at a distance of 20 cm from its pole.

1. Which type of mirror should the student use?
2. Find the magnification of the image produced.
3. Find the distance between the object and its image.
4. Draw a ray diagram to show the image formation in this case and mark the distance between the object and its image.

What is meant by advance sunrise and delayed sunset? Draw a labelled diagram to explain these phenomena.

"Energy flow in a food chain is unidirectional" Justify this statement.

"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

Explain the following:- Speciation

List four factors that could lead to speciation. Which of them cannot be a major factor in the speciation of a self-pollinating plant species?. Give reason to justify your answer.

Define nutrition. 

Define the terms 'nutrients'.

List two differences between 'Holozoic nutrition' and 'Saprophytic nutrition'. Give two examples of each of these two types of nutrition.

Identify A, B, C and D in the given diagram and write their names.

Answer the following question.

What is pollination? Explain the different types of pollination.

Answer the following question.
State significance of pollination.

How does fertilisation occur in flowers? Name the parts of the flower that develop into (i) seed, and (ii) fruit after fertilisation.

What is meant by a power of a lens? Define its SI unit. 

Name the type of lens whose power is positive.
The image of an object formed by a lens is real, inverted and of the same size as the object. If the image is at a distance of 40 cm from the lens, what is the nature and power of the lens ? Draw ray diagram to justify your answer.

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

Distance of flame from the mirror = 18 cm

If the flame is perpendicular to the principal axis of the mirror, then calculate the following:

1. Distance of the image from the mirror
2. 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.

State the function of each of the following parts of the human eye:

(i) Cornea

(ii) Iris

(iii) Pupil

(iv) Retina

Millions of people of the developing countries are suffering from corneal blindness. This disease can be cured by replacing the defective cornea with the cornea of a donated eye. Your school has organised a campaign in the school and its neighbourhood in order to create awareness about this fact and motivate people to donate their eyes after death. How can you along with your classmates contribute in this noble cause? State the objectives of organising such campaigns in schools.

Elements forming ionic compounds attain noble gas electronic configuration by either gaining or losing electrons from their valence shells. Explain giving reason why carbon cannot attain such a configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also explain the reason why carbon compounds are generally poor conductors of electricity.

‘A’ is an element having four electrons in its outermost orbit. An allotropes ‘B’ of this element is used as a dry lubricant in machinery and in pencil leads. So:
i. Write the name of element ‘A’ and its allotropes.
ii. State whether ‘B’ is a good conductor or non-conductor of electricity?

‘E’ is an element which reacts with oxygen to form an oxide E₂O. An aqueous solution of E₂O turns red litmus blue, so:
i. What is the nature of oxide E₂O ?
ii. Write the name of element ‘E’.

A student obtained on a screen the sharp image of a candle flame placed at the farther end of laboratory table using a concave mirror. For getting better value of focal length of the mirror, the teacher suggested to him to focus the sun. What should the student do?
(A) Should move the mirror away from the screen.
(B) Should move the mirror towards the screen.
(C) Should move the mirror and screen both towards the sun.
(D) Should move only the screen towards the sun.

While determining the focal length of a convex lens, you try to focus the image of a distant object formed by the lens on the screen. The image formed on the screen, as compared to the object, should be
(A) erect and highly diminished
(B) erect and enlarged
(C) inverted and enlarged
(D) inverted and highly diminished

In which of the following four diagrams is the correct path of a ray of light passing through a glass prism shown ?

Which of the following is the best experimental set-up out of the four shown for tracing the path of a ray of light passing through a rectangular glass slab ?

A student takes 4 mL of distilled water in each of four test tubes I, II, III and IV, and then dissolves an equal amount of four different salts namely NaCl in I, CaCl₂ in II, MgCl₂ in III and KCl in IV. He then adds 8 drops of the given soap solution to each test tube and shakes the contents of the test tube 10 times. In which test tubes will enough lather (foam) be formed ?
(A) I and II
(B) II and III
(C) I and IV
(D) III and IV

A student puts a drop of acetic acid first on a blue litmus paper and then on a red litmus paper. He would observe that
(A) the red litmus paper turns colourless and there is no change in the blue litmus paper.
(B) the red litmus paper turns blue and the blue litmus paper turns red.
(C) there is no change in the red litmus paper and the blue litmus paper turns red.
(D) there is no change in the blue litmus paper and the red litmus paper turns blue.

While studying saponification reactions, the following comments were noted down by the students :
(I) Soap is a salt of fatty acids.
(II) The reaction mixture is basic in nature.
(III) In this reaction heat is absorbed.
(IV) This reaction is not a neutralisation reaction.
Which of these are the correct comments ?
(A) I and III only
(B) I, II and III
(C) II, III and IV
(D) I and II only

In a class, students were asked to observe the models/slides/pictures of the skeletons of forelimbs and wings of different organisms. After the observations the students made the following groups of homologous structures. Select the correct group :
(A) Wings of a bird and a butterfly
(B) Wings of a pigeon and a bat
(C) Wings of a butterfly and a bat
(D) Forelimbs of a cow, a duck and a lizard

A student is asked to study the different parts of an embryo of pea seeds. Given below are the essential steps for the experiment :
(I) Soak the pea seeds in plain water and keep them overnight.
(II) Cut open the soaked seed and observe its different parts.
(III) Take some pea seeds in a petri dish.
(IV) Drain the excess water. Cover the seeds with a wet cotton cloth and leave them as it is for a day.
The correct sequence of these steps is
(A) III, I, IV, II
(B) III, IV, I, II
(C) III, I, II, IV
(D) III, II, I, IV

A student places a 8.0 cm tall object perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. He obtains a sharp image of the object on a screen placed on the other side of the lens. What will be the nature (inverted, erect, magnified, diminished) of the image he obtains on a screen? Draw ray diagram to justify your answer.

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.

A student in viewing under a microscope a permanent slide showing various stages of asexual reproduction by budding in yeast. Draw diagrams of what he observes (in proper sequence)