Q. To construct a ray diagram, we use two light rays which are so chosen that it is easy to know their directions after reflection from the lens. List these two rays and state the path of these rays after refraction. Use these two rays to locate the image of an object placed between '$F$' and '$2F$' of a convex lens.

Q. On adding acetic acid to sodium hydrogen carbonate in a test tube, a student observed :

1. no reaction
2. a colourless gas with pungent smell
3. bubbles of a colourless and odourless gas
4. a strong smell of vinegar

Q. The aqueous solutions of copper sulphate and zinc sulphate appear :

1. blue and green respectively
2. blue and brown respectively
3. green and colourless respectively
4. blue and colourless respectively

Q. List the products of combustion of fossil fuels. What are their adverse effects on the environment?

Q. A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 24 cm. The distance of the object from the lens is 16 cm. Find the position, size and nature of the image formed, using the lens formula.

Q. On adding 2 mL acetic acid to 2 mL of water in a test tube, it was observed that :

Q. An element 'X' belongs to $3^{rd}$ period and group 17 of the periodic table. State its (i) electronic configuration, (ii) valency. Justify your answer with reasoning.

Q. In a food chain, if 10, 000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer?

Q. List and explain in brief three methods of contraception.

Q. An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.

Q. A star appears slightly higher (above) than its actual position in the sky. Illustrate it with the help of a labelled diagram.

Q. What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere?

Q. Which one of the following are the correct observations about acetic acid?

1. It turns blue litmus red and smells like burning sulphur
2. It turns red litmus blue and has a fruity smell
3. It turns red litmus blue and smells like vinegar
4. It turns blue litmus red and smells like vinegar

Q. Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solution. After some time a change will be observed in:

1. I and II
2. II and III
3. III and I
4. All of the above

Q. What are hydrocarbons? Write the name and general formula of (i) saturated hydrocarbons, (ii) unsaturated hydrocarbons and draw the structure of one hydrocarbon of each type. How can an unsaturated hydrocarbon be made saturated?

Q. List in tabular form two distinguishing features between acquired traits and inherited traits, with one example of each.

Q. A student has to determine the focal length of a concave mirror by obtaining the image of a distant object on a screen. For getting best result he should focus:

1. a distant tree or an electric pole
2. a well-illuminated distant building
3. a burning candle placed at the distant edge of the laboratory table
4. well-lit grills of the nearest window

Q. What is meant by homologous series of organic compounds? Write the chemical formulae of two members of a homologous series and state which part determines the (i) physical properties, (ii) chemical properties, of these compunds.

Q. Choose from the following:
${}_{6}C,{}_{8}O,{}_{10}Ne,{}_{11}Na,{}_{14}Si$
(i) Elements that should be in the same period
(ii) Elements that should be in the same group
State reason for your selection in each case:

Q. State one function of iris in human eye.

Q. Write the name and formula of the second member of the carbon compounds having functional group-OH.

Q. Name an organism which reproduces by spore formation. List three conditions favourable for spores to germinate and grow.

Q. Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing process of germination of pollen grains on stigma and label the following parts:
(i) Female germ cell
(ii) Male germ cell
(iii) Ovary

Q. Draw a labelled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.

Q. List three problems which arise due to construction of big dams. Suggest a solution for these problems.

Q. State the types of mirrors used for (i) headlights and (ii) rear view mirrors, in cars and motorcycles. Give reason to justify your answer in each case :

Q. How are fossils formed? Describe, in brief, two methods of determining the age of fossils.

Q. If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get Pea plant of $F_1$ generation, then we obtain Pea plants of $F_2$ generation.
(a) What do the plants of $F_1$ generation look like?
(b) State the ratio of tall plants to dwarf plants in $F_2$ generation.
(c) State the type of plants not found in $F_1$ generation but appeared in $F_2$ generation, mentioning the reason for the same.

Q. Na, Mg and Al are the elements having one, two and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive? Justify your answer stating reason for each.

Q. List the new Cartesian sign convention for reflection of light by spherical mirrors. Draw a diagram and apply these conventions for calculating the focal length and nature of a spherical mirror which forms a $1/3$ times magnified the virtual image of an object placed $18cm$ in front of it.