Case study ( 4 Marks )

Question 14 Marks

Homogeneous mixtures are regarded as solutions or true solutions. Heterogeneous mixtures are of two types. These are suspensions and colloidal solutions. These differ in the size of the particles responsible for the difference in their properties. In a suspension, the particle size is more than $10^{-5} cm$ whereas in a colloidal solution, it ranges between $10^{-5} cm$ to $10^{-7} cm$. The two phases which constitute colloidal solutions, are dispersed phase and dispersion medium. Based upon their nature, the colloidal solutions are classified into eight types. The mixture of the non-reacting gases is always homogeneous irrespective of their nature. Therefore, it is not a colloidal solution.
i. Scattering of light occurs when a beam of light is passed through Blood. Why?
ii. What is Tyndall effect?
iii. What is called colloidal solution?
OR
Give an example of colloidal solution and identified their dispersed phase and dispersion medium?

Answer

i. Since blood is a colloid, so tyndall effect is observed when a beam of light is passed through it since the dispersed particles of a colloid are large, deflect light.
ii. The phenomenon by which the colloidal particles scatter light is called Tyndall effect. If light is passed through a colloid the light is scattered by the larger colloidal particles and the, beam becomes visible.
iii. Colloidal solutions area mixture in which the substances are regularly suspended in a fluid. A colloid is a very tiny and small material that is spread out uniformly all through another substance.
OR
Fog: Liquid (water drops) acts as dispersed phase and gas (air) as the dispersion medium.

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Question 24 Marks

Crop Season: Different crops require different climatic conditions like temperature, moisture and photoperiods to grow well and complete their life cycle.
The Indian cropping season is classified into two main seasons- (i) Kharif and (ii) Rabi based on the monsoon.
The characteristics of these two main crop seasons are

i. Mention the various cropping seasons in India.
ii. Differentiate between Rabi and Kharif crops.
iii. If there is low rainfall in a village throughout the year, what measures will you suggest to the farmers for better cropping?
OR
What is zaid crop? Give example.

Answer

i. The various cropping seasons in India are Rabi crop, Kharif crop and Zaid crop.
ii. Rabi crops are sown during the winter season which requires less water.Kharif crop is sown during the summer/rainy season which requires abundant water.
iii. Farmers are suggested to grow drought-resistant crops that can mature early. Along with this farmers are advised to use manure for their fields as it increases the water-holding capacity of the soil.
OR
There is a short season between Kharif and Rabi season in the months of March to July. The crops that grow in this season are Zaid crops. These crops are grown on irrigated lands and do not have to wait for monsoons. Some examples of Zaid types of crops are pumpkin, cucumber, and bitter gourd.

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Question 34 Marks

The covering or protective tissues in the animal body are epithelial tissues. Epithelium covers most organs and cavities within the body. It also forms a barrier to keep different body systems separate. Epithelial tissue cells are tightly packed and form a continuous sheet. The skin, which protects the body, is also made of squamous epithelium. Skin epithelial cells are arranged in many layers to prevent wear and tear. This columnar epithelium facilitates movement across the epithelial barrier. In the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like projections on the outer surfaces of epithelial cells. Cuboidal epithelium forms the lining of kidney tubules.
i. Identify the type of epithelial tissue shown in the following figure.

ii. Which cell is present in the inner lining of the intestine?
iii. Is excretion is the main function of the cuboidal epithelium?
OR
Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is formed which is called a?

Answer

i. Columnar.
ii. columnar epithelial.
iii. No, providing mechanical support is the main function of the cuboidal epithelium.
OR
Glandular epithelium.

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Science Case study ( 4 Marks )

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