Q4 of 360 Page 119

What is the basis of long life of pickles and jams? What lesson one gets from this fact?

Pickles and jams have high concentration of salt and sugar respectively which are osmotically active substances and do not allow microbial spores to germinate. Even if pickles or jams get contaminated, the microorganisms cannot survive as they undergo exosmosis and ultimately die.

Moreover, turmeric or acetic acid used act as preservatives and kill the microbes. Thus, pickles and


jams get a longer life and do not get easily spoiled. Their life is further enhanced by keeping them in


dry and cool place and using neat and moisture-free spoons.


This gives us a lesson that human beings can also have a long life if they live in a hygienic environment.


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2

Khushi wanted to eat rice and kidney bean (rajmah). She requested her mother to cook the same for lunch tomorrow. At night her mother took a cup of kidney bean and put them in a container having some water. She kept the container covered overnight. Next morning, she cooked rice and kidney beans for lunch. Khushi inquired her mother the following questions:

(i) Why dis dhe soak jkidney beans in water overnight?


(ii) Name the scientific phenomenon involved in above process.


(iii) name atleast one more food item that is cooked in this way.

 3

One day Muskan saw her mother making pickle. Her mother cut the carrots, turnip and cauliflowers into small pieces, washed them and put them in the sun for few hours. Thereafter, she mixed common salt, oil, paste of onion, ginger and garlic, gur, red chilli, turmeric powder, acetic acid, etc. As per requirement with the cut vegetables and heated them. After cooling, she put the contents in the air tight jar and kept it in the sun for many days.

(i)Why did Muskan’s mother cur the vegetables into small pieces and put them in the sun for few hours?


(ii) Why did she mix common salt in the cut vegetables and heated it? Name the process involved.


(iii) Why did she mix acetic acid?

 5

Arvind sometimes go for late ecening walk with his father who has a background of biology. While walking in the colony park, he observed many plants having colour flowers. He also saw gew plants having white flowers. Most of these flowers emit pleasant fragrance (=aroma). Out of curiousity, Arvind asked his father the following questions:

(i) Why do plants have variously coloured flower? Give two reasons.


(ii) Why do certain flowers emit frangrance? How does frangrance of flowers spread in the environment?


(iii) Which scientific phenomenon is obvolved when (a) frangrance spreads in the house at the time of cooking of food in the kitchen; (b) exchange of gases occurs across the respiratory surface.

 7

What are the functions of plasma membrane? How is the plasma membrane able to perform diverse functions. Give an example of diversity in functioning in any segment of human society.