Q. Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential conditions required for an addition reaction to occur, write the chemical equation giving the name of the reactant and the product of such a reaction.

Q. A student wants to project the image of a candle flame on the walls of school laboratory by using a lens :
(a) Which type of lens should he use and why ?
(b) At what distance in terms of focal length `f ' of the lens should he place the candle flame so as to get (i) a magnified, and (ii) a diminished image respectively on the wall ?
(c) Draw ray diagram to show the formation of the image in each case.

Q. List four advantages of vegetative propagation.

Q. A student adds a few drops of ethanoic acid to test tubes $X,Y$ and $Z$ containing aqueous solutions of sodium chloride, sodium hydroxide and sodium carbonate respectively. If he now brings a burning splinter near the mouth of the test tubes immediately after adding the ethanoic acid in each one of them, in which of the test tube or test tubes the flame gets extinguished?

1. X and Y
2. Y and Z
3. X and Z
4. Only Z

Q. When you add about 2 mL of acetic acid to a test tube containing an equal amount of distilled water and leave the test tube to settle after shaking its contents, then after about 5 minutes what will you observe in the test tube?

1. A white precipitate settling at its bottom
2. A layer of water over the layer of acetic acid
3. A clear colourless solution
4. A layer of acetic acid over the layer of water

Q. Why is government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment.

Q.

Q. (a) List three common refractive defects of vision. Suggest a way of correcting these defects.
(b) About $45lac$ people in developing countries are suffering from corneal blindness. About $30lac$ children below the age of $12$ years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?

Q. A spherical mirror produces an image of magnification -1 on a screen placed at a distance of 50 cm from the mirror.
(a) Write the type of mirror.
(b) Find the distance of the image from the object.
(c) What is the focal length of the mirror ?
(d) Draw the ray diagram to show the image formation in this case.

Q. State the reason why carbon can neither form $C^{4+}$ cations nor $C^{4-}$ anions but forms covalent compounds. Also, state reasons to explain why covalent compounds:
(i) are bad conductors of electricity?
(ii) have low melting and boiling points?

Q. What is meant by biodiversity? List two advantages of conserving forest and wildlife as regions of biodiversity.

Q. A student takes about 6 ml of distilled water in each of the four test tubes $P$, $Q$, $R$ and $S$, then dissolves an equal amount of four different salts namely sodium chloride in $P$, potassium chloride in $Q$, calcium chloride in $R$ and magnesium chloride in $S$. He then adds 10 drops of soap solution to each test tube and shakes its contents. The test tubes in which scum (insoluble substance) is formed with soap are:

1. $P$ and $Q$
2. $Q$ and $R$
3. $Q$ and $S$
4. $R$ and $S$

Q. On the basis of their experiment, "To trace the path of a ray of light through a rectangular glass slab, " students of a class arrived at which one of the following conclusions :

1. Emergent ray is parallel to the refracted ray.
2. Incident ray and emergent ray are parallel to each other.
3. Angle of incidence is greater than the angle of emergence,
4. Angle of emergence is smaller than the angle of refraction.

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Q.
In order to study saponification reaction we first prepare 20% solution of sodium hydroxide. If we record the temperature of this solution just after adding sodium hydroxide flakes to water and also test its nature using litmus, it may be concluded that the process of making this solution is :

1. exothermic and the solution is alkaline
2. endothermic and the solution is alkaline
3. endothermic and the solution is acidic
4. exothermic and the solution is acidic

Q. Draw diagrams to explain the regeneration that takes place in each of the body parts of planaria when its body is cut into three pieces. Name any other organism in which a similar process can be observed.

Q. (a) Name the respective part of human female reproductive system
(i) That produces eggs
(ii) fusion of egg and sperm takes place
(iii) Zygote gets implanted
(b) Describe in brief what happens to the zygote after it gets implanted

Q. List four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?

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Q.

Based on the group valency of elements state the formula for the following giving justification for each:

(i) Oxides of 1st group elements.

(ii) Halides of the elements of group 13.

(iii) Compounds formed when an element of group 2 combines with an element of group 16.

Q. A student has obtained an image of a distant object on a screen to determine the focal length $F_1$ of the given lens. His teacher after checking the image, gave him another lens of focal length $F_2$ and asked to focus the same object on the same screen. The student found that to obtain a sharp image he has to move the lens away from the screen. From this finding we may conclude that both the lenses given to the student were :

1. Concave and $F_1<F_2$
2. Convex and $F_1<F_2$
3. Concave and $F_1>F_2$
4. Convex and $F_1>F_2$

Q. A student has obtained the image of a distant object with a concave mirror to determine its focal length. If he has selected a well illuminated red building as object, which of the following correctly describes the features of the image formed ?

1. Virtual, inverted, diminished image in red shade
2. Real, erect, diminished image in pink shade
3. Real, inverted, diminished image in red shade
4. Virtual, erect, enlarged image in red shade

Q. State the meaning of functional group in a carbon compound. Write the functional group present in (i) ethanol and (ii) ethanoic acid and also draw their structures.

Q. While studying saponification reaction for the preparation of soap, the teacher suggested to a student to add a small quantity of common salt to the reaction mixture. The function of common salt in this reaction is to:

1. reduce the alkalinity of the soap
2. reduce the acidity of the soap
3. enhance the cleansing capacity of soap
4. favour precipitation of soap

Q. (a) Give one example each of a unisexual and a bisexual flower.
(b) Mention the changes a flower undergoes after fertilization.
(c) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?

Q. Write the number of vertical columns in the modern periodic table. What are these columns called?

Q. Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is directed towards the principal focus of a convex mirror. Mark on it the angle of incidence and the angle of reflection.

Q. Water is a valuable resource. List two ways that you would suggest every family member to save this resource.

Q. Study the following four experimental set-ups I, II, III and IV for the experiment, "To trace the path of a ray of light through a rectangular glass slab."
Which of the marked set-ups is likely to give best results (P1 and P2 are the positions of pins fixed on the incident ray) ?

1. IV
2. I
3. II
4. III

Q. The path of a ray of light passing through a glass prism is shown below :
In this diagram the angle of prism, angle of incidence, angle of emergence and angle of deviation respectively have been represented by:

1. O, Y, Z and N,
2. P, Y, M and Z,
3. O, X, M and Z
4. P, X, Z and N