Q. Given below are some elements of the modern periodic table:
${}_{4}Be,{}_{26}Fe,{}_{14}Si,{}_{19}K,{}_{20}Ca$

Q. Read the following statements:
I. When a red litmus paper is dipped into reaction mixture of a saponification reaction, it turns blue and the reaction is exothermic.
II. When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is exothermic.
III. When a red litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is endothermic.
IV. When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is endothermic.
Which of the above statements are correct?

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

Q. Write the number of periods the modern periodic table has. How do the valency and metallic character of element vary on moving from left to right in a period? How do the valency and atomic size of elements vary down a group?

Q. (a) State the laws of refraction of light. Give an expression to relate the absolute refractive index of a medium with speed of light in vacuum.
(b) The refractive indices of water and glass with respect to air are 4/3 and 3/2 respectively. If the speed of light in glass is $2\times {10}^{8}m{s}^{-1}$, find the speed of light in (i) air, (ii) water.

Q. (a) Identify A, B and C in the given diagram and write their functions.
(b) Mention the role of gamete and zygote in sexually reproducing organisms.

Q. (a) What is an ecosystem? List its two main components.
(b) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain.

Q. Write two examples each of sexually transmitted diseases caused by (i) virus, (ii) bacteria. Explain how the transmission of such diseases be prevented?

Q. "A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself." Draw labelled ray diagram to justify the statement.

Q. (a) A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
(b) We see advertisements for eye donation on television or in newspapers. Write the importance of such advertisements.

Q. Write the name and the structural formula of the compound formed when ethanol is heated at 443 K with excess of conc. $H_{2}S{O}_4$. State the role of conc. $H_{2}S{O}_4$ in the reaction. Write chemical equation for the reaction.

Q. Why should biodegradable and non-biodegradable wastes be discarded in two separate dust bins?

Q. A student focused the image of a distant object using a device 'X' on a white screen 'S' as shown in the figure. If the distance of the screen from the device is 40 cm, select the correct statement about the device.

1. The device X is a convex lens of focal length 40 cm.
2. The device X is a concave mirror of radius of curvature 40 cm.
3. The device X is a convex lens of focal length 20 cm.
4. The device X is a concave mirror of focal length 40 cm.

Q. List and explain any two advantages associated with water harvesting at community level.

Q. Tabulate two distinguishing features between acquired traits and inherited traits with one example of each.

Q. State the difference in colours of the sun observed during sunrise/sunset and noon. Give explanation for each.

Q. An object of height 6 cm is placed perpendicular to the principal axis of a concave lens of focal length 5 cm. Use lens formula to determine the position, size and nature of the image if the distance of the object from the lens is 10 cm.

Q. What is speciation?

Q. In an experiment to study the properties of acetic acid, a student takes about 2 mL of acetic acid in a dry test tube. He adds about 2 mL of water to it and shakes the test tube well. He is likely to observe that:

1. the solution becomes light orange
2. water floats over the surface of acetic acid
3. acetic acid floats over the surface of water
4. the acetic acid dissolves readily in water

Q. "The chromosomes number of the sexually reproducing parents and their offspring is the same." Justify this statement.

Q. A student obtained a sharp image of a burning candle, placed at the farther end of a laboratory table, on a screen using a concave mirror. For getting better value of focal length of the mirror, the subject teacher suggested him for focussing a well illuminated distant object. What should the student do?

Q. (a) Define the term 'isomers'.
(b) Draw two possible isomers of the compounds with molecular formula $C_3{H}_{6}O$ and write their names.
(c) Give the electron dot structures of the above two compounds.

Q. How many vertical columns are there in the modern periodic table and what are they called?

Q. (a) List three distinguishing features between sexual and asexual types of reproduction.
(b) Explain why variations are observed in the offspring of sexually reproducing organisms?

Q. (a) Explain the process of regeneration in Planaria.
(b) How is regeneration different from reproduction?

Q. A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below.
I. Sodium hydroxide is in the form of pellets.
II. It dissolves in water readily.
III. The beaker appears cold when touched from outside.
IV. The red litmus paper turns blue when dipped into the solution.
The correct observation are :

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

Q. Hard water required for an experiment is not available in a school laboratory. However, the following salts are available in the laboratory. Select the salts which may be dissolved in water to make it hard for the experiment :

1. 1, 2 and 4
2. 1, 3 and 6
3. 3, 5 and 6
4. 2, 4 and 5

Q. "The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it." Justify this statement with the help of flow chart showing determination of sex of a newborn.

Q. Why homologous series of carbon compounds are so called? Write chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their (i) physical properties, and (ii) chemical properties?

Q. We often observe domestic waste decomposing in the bylanes of residential colonies. Suggest ways to make people realise that the improper disposal of waste is harmful to the environment.

Q. A student takes 2 mL acetic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He makes the following observations:
I. A colourless and odourless gas evolves with a brisk effervescence.
II. The gas turns lime water milky when passed through it.
III. The gas burns with an explosion when a burning splinter is brought near it.
IV. The gas extinguishes the burning splinter that is brought near it.
The correct observations are:

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