Q. When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

1. No reaction takes place
2. A colourless and odourless gas is released with brisk effervescence
3. A brown coloured gas is released with brisk effervescence
4. Colour of solution changes

Q. (a) A student suffering from myopia is not able to see distinctly the objects placed beyond $5m$. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain
(i) why the student is unable to see distinctly the objects placed beyond $5m$ from his eyes.
(ii) the type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.
(b) If, in this case, the numerical value of the focal length of the corrective lens is $5m$, find the power of the lens as per the new Cartesian sign convention.

Q. While studying the saponification reaction, what do you observe when you mix an equal amount of colourless vegetable oil and 20% aqueous solution of $NaOH$ in a beaker?

1. The colour of the mixture has become dark brown
2. A brisk effervescence is taking place in the beaker
3. The outer surface of the beaker has become hot
4. The outer surface of the beaker has become cold

Q. Study the given ray diagrams and select the correct statement from the following:

1. Device X is a concave lens and device Y is a convex mirror, whose focal lengths are 20cm and 25cm respectively.
2. Device X is a concave lens and device Y is a concave mirror, whose focal lengths are 20cm and 25cm respectively.
3. Device X is a concave mirror and device Y is a convex lens, whose focal lengths are 20cm and 25cm respectively.
4. Device X is a convex lens and device Y is a concave mirror, whose focal lengths are 20cm and 25cm respectively.

Q. A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory there are hard water. Select from the following groups of salts, a group, each salt of which when dissolved in distilled water will make it hard.

1. Sodium chloride, Potassium chloride
2. Sodium sulphate, Potassium sulphate
3. Sodium sulphate, Calcium sulphate
4. Calcium sulphate, Calcium chloride

Q. Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.

Q. Why is an equitable distribution of resources essential in society? List two forces which are against such distribution.

Q. In the following food chain, plants provide $500J$ of energy to rats. How much energy will be available to hawks from snakes?
$Plants\to Rats\to Snakes\to Hawks$

Q.

S.No.	Object-Distance u(cm)	Image-Distance v(cm)
1.	-100	+25
2.	-60	+30
3.	-40	+40
4.	-30	+60
5.	-25	+100
6.	-15	+120

Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations
What is the focal length of the convex lens? Give reason to justify your answer.

Q. Select an appropriate scale and draw a ray diagram for the observation at S.No.2. Also find the approximate value of magnification.

Q. $Na,Mg$ and $Al$ are the elements of the $3^{rd}$ period of the Modern Periodic Table having group number 1, 2 and 13 respectively. Which one of these elements has the (a) highest valency, (b) largest atomic radius and (c) maximum chemical reactivity? Justify your answer stating the reason for each.

Q. "Evolution and classification of organisms are interlinked." Give reasons to justify this statement.

Q. What is 'dispersion of white light'? State its cause. Draw a ray diagram to show the dispersion of white light by a glass prism.

Q. Newly formed DNA copies may not be identical at times. Gives one reason.

Q. Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion?

Q. With the help of one example for each, distinguish between the acquired traits and the inherited traits. Why are the traits/experiences acquired during the entire lifetime of an individual not inherited in the next generation? Explain the reason of this fact with an example.

Q. Draw ray diagrams to show the formation of three times magnified (a) real, and (b) virtual image of an object by a converging lens. Mark the positions of O, F and 2F in each diagram.

Q. (a) Water is an elixir life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, "How to save water, the vital natural resource." Write any two ways that you will suggest to bring awareness in your neighbourhood, on 'how to save water.'
(b) Name and explain any one way by which the underground water table does not go down further.

Q. Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.

Q. What happens when (write chemical equation in each case)
(1) ethanol is burnt in air?
(2) ethanol is heated with excess $conc.H_{2}S{O}_4$ at $443K$?
(3) a piece of sodium is dropped into ethanol?

Q. List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males? How does the use of these techniques have a direct impact on the health and prosperity of a family?

Q. A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence $\left(\angle i\right)$. He then measures the corresponding values of the angle of refraction $\left(\angle r\right)$ and the angle of emergence $\left(\angle e\right)$ for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be

1. $\angle i>\angle r>\angle e$
2. $\angle i=\angle e>\angle r$
3. $\angle i,\angle r,\angle e$
4. $\angle i=\angle e,\angle r$

Q. (a) If the image formed by a mirror for all positions of the object placed in front of it is always diminished, erect and virtual, state the type of the mirror and also draw a ray diagram to justify your answer. Write one use such mirrors are put to and why.
(b) Define the radius of curvature of spherical mirrors. Find the nature and focal length of a spherical mirror whose radius of curvature is $+24cm$.

Q. (a) Write the functions of each of the following parts in a human female reproductive system:

Q. With the help of two suitable example, explain why certain experiences and traits earned by people during their lifetime are not passed on to their next generations. When can such traits be passed on?

Q. Why are certain compounds called hydrocarbons? Write the general formula for homologous series of alkanes, alkenes and alkynes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkanes and also write a chemical equation to show the necessary conditions for the reaction to occur.

Q. An object is placed at a distance of $15cm$ from a convex lens of focal length $20cm$. List four characteristics (nature, position, etc.) of the image formed by the lens.

Q. Describe reproduction by spores in Rhizopus.

Q. Write the molecular formula of the $2^{nd}$ and $3^{rd}$ number of the homologous series whose first member is ethene.

Q. Why must we conserve our forests? List two factors responsible for causing deforestation.