Q35 of 36 Page 1

Trace the changes that take place in a flower from gamete formation to fruit formation.


[Diagram drawn and annotated with the following points will also be considered ]


- Stamen is the male reproductive part and it produces pollen grains.


The ovary contains ovules and each ovule has an egg cell.


The pollen needs to be transferred from the stamen to the stigma.


If this transfer of pollen occurs in the same flower, it is referred to as self-pollination. On the other hand, if the pollen is transferred from one flower to another, it is known as cross-pollination.


After the pollen lands on a suitable stigma, it has to reach the female germ-cells which are in the ovary. For this, a tube grows out of the pollen grain and travels through the style to reach the ovary.


The male germ-cell produced by pollen grain fuses with the female gamete(egg) present in the ovule.


This fusion of the germ-cells or fertilisation gives the zygote.


After fertilisation, the zygote divides several times to form an embryo within the ovule.


The ovule develops a tough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit.


Meanwhile, the petals, sepals, stamens, style and stigma may shrivel and fall off during this process.


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32

a. Explain the formation of Calcium Chloride with the help of electron dot structure. (At numbers: Ca = 20; Cl = 17)

b. Why do ionic compounds not conduct electricity in solid state but conduct electricity in molten and aqueous state?


 33

Refractive index of water with respect to air is 1.33 and that of diamond is 2.42.

(i) In which medium does the light move faster, water or diamond?


(ii) What is the refractive index of diamond with respect to water?


 34

Match the following pH values 1, 7, 10, 13 to the solutions given below:

• Milk of magnesia


• Gastric juices


• Brine


• Aqueous Sodium hydroxide.


Amit and Rita decided to bake a cake and added baking soda to the cake batter


Explain with a balanced reaction, the role of the baking soda. Mention any other use of baking soda.


OR


(i) Four samples A, B, C and D change the colour of pH paper or solution to Green, Reddish-pink, Blue and Orange. Their pH was recorded as 7, 2, 10.5 & 6 respectively. Which of the samples has the highest amount of Hydrogen ion concentration? Arrange the four samples in the decreasing order of their pH.


(ii) Rahul found that the Plaster of Paris, which he stored in a container, has become very hard and lost its binding nature. What is the reason for this? Also, write a chemical equation to represent the reaction taking place.


(iii) Give any one use of Plaster of Paris other than for plastering or smoothening of walls.


 36

In the given circuit, A, B, C and D are four lamps connected with a battery of 60V.


Analyse the circuit to answer the following questions.


(i) What kind of combination are the lamps arranged in (series or parallel)?


(ii) Explain with reference to your above answer, what are the advantages (any two) of this combination of lamps?


(iii) Explain with proper calculations which lamp glows the brightest?


(iv) Find out the total resistance of the circuit.


OR


PQ is a current carrying conductor in the plane of the paper as shown in the figure below.



(i) Find the directions of the magnetic fields produced by it at points R and S?


(ii) Given r1> r2, where will the strength of the magnetic field be larger? Give reasons.


(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?


(iv) Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor.