how do organisms reproduce ? — Science STD 10 — Question

Ionic compounds are non-conductor in the solid state, but they conduct electricity in the molten state or in an aqueous solution.

Explain in brief : Biomagnification

Give scientific reason:
The number of bryophyllum keep on increasing in garden.

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Five solutions A, B, C, D and E, when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is...
(a) neutral?  (b) strongly alkaline?  (c) strongly  acidic ?  (d) weakly acidic?  (e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Rita's mother had severe pain when a honeybee stung her on hand. Rita's grandmother tried to relieve the pain by rubbing a iron metal on the affected area. But, Rita took the baking powder from the kitchen and applied on her mother's hand which quickly relieved the pain.
(1) Why do honeybee stinging causes pain?
(2) How does baking powder relieve the bee- sting pain?
(3) What values of Rita is seen in the above act?

Write a note on ‘Chipko Andolan’

(1) What are the changes seen in girls at the time of puberty? (2) What are the changes seen in the boys at the time of puberty? ### What are the changes seen in girls at the time of puberty?

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.

An electric oven of 2 kW power rating is operated in a domestic electric circuit ( 220 V ) that has a current rating of 5 A . What result do you expect? Explain.