Metals and Non-Metals — Science STD 10 — Question

Suggest three contraceptive methods to control the size of human population which is essential for the health and prosperity of a country. State the basic principle involved in each.

How does the resistance of a wire change when:

1. Its length is tripled?
2. Its diameter is tripled?
3. Its material is changed to one whose resistivity is three times?

What happens when an acid reacts with a base? Explain by taking the example of hydrochloric acid and sodium hydroxide. Give equation of the chemical reaction which takes place. What is the special name of such a reaction?

Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Name the functional group of organic compounds that can be hydrogenated. With the help of suitable example explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.

What are fossils? Giving one example, explain how fossils provide evidence for evolution.

"Our food grains such as wheat and rice, the vegetables and fruits and even meat are found to contain varying amounts of pesticide residues." State the reason to explain how and why it happens?

An object placed 45cm from a lens forms an image on a screen place 90cm on the other side of the lens. Identify the type of the lens and find its focal length.

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.

Draw a simple diagram of the human eye and label clearly the cornea, iris, pupil, ciliar muscles, eye-lens, retina, optic nerve and blind spot.