Acids, Bases and Salts — Science STD 10 — Question

State the three common features of all the respiratory organs like skin, gills and lungs.

Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?

When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.

1. What are X, Y and Z?
2. Write equations for the reactions which take place:

1. When limestone reacts with dilute HCl.
2. When gas X reacts with lime water to form white precipitate Y.
3. When excess of gas X dissolves white precipitate Y to form a soluble compound Z.

Explain how tidal energy can be used to generate electricity.

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

P, Q, R and S are four major types of phytohormones. P is a phytohormone which functions mainly as a growth inhibitor. It promotes the wilting and falling of leaves. Q, R and S are phytohormones which all promote growth of plants in various ways. Q is responsible for the phenomenon of phototropism in plants. R is involved mainly in shoot extensions. The phytohormone S helps in breaking the dormancy of seeds and buds. What are P, Q, R and S? Give one reason each for your choice.

Make two diagrams to explain refraction and dispersion.

How to destarch the leaves for an experiment to show that sunlight is necessary for photosynthesis?