Heredity and Evolution — Science STD 10 — Question

What are the main uses of coal and petroleum products?

An element has electronic configuration 2, 8, 7.

1. To which group and period of the long form of Periodic Table does it belong?
2. What is atomic number of this element?
3. Is it metallic or non-metallic and why?
4. Identify the element.
5. Name an element chemically similar to this element.

Reproduction is essentially a phenomenon that is not for survival of an individual but for the stability of a species. Justify.

When metal X is treated with a dilute acid Y, then a gas Z is evolved which burns readily by making a little explosion.

1. Name any two metals which can behave like metal X.
2. Name any two acids which can behave like acid Y.
3. Name the gas Z.
4. Is the gas Z lighter than or heavier than air?
5. Is the reaction between metal X and dilute acid Y, exothermic or endothermic?
6. By taking a specific example of metal X and dilute acid Y, write a balanced chemical equation for the reaction which takes place. Also indicate physical states of all the reactants and products.

Suggest suitable mechanism (s) for waste management in fertilizer industries.

1. Define optical centre of a spherical lens.
2. A divergent lens has a focal length of 20cm. At what distance should an object of height 4cm from the optical centre of the lens be placed so that its image is formed 10cm away from the lens. Find the size of the image also.
3. Draw a ray diagram to show the formation of image in above situation.

A thickened underground stem X of a plant which is swollen with stored food has a number of points Y on its surface. When the old stem X is planted in the soil of a field in the next growing season, then each point Y present on its surface grows into a new plant.

1. What is the general name of the underground stems like X?
2. Give one example of X.
3. What are points Y present on X known as?
4. Is it necessary to plant the whole of stem X in the ground to obtain its new plants? Explain your answer.
5. What is the name of this method of reproduction of plants?
6. What is the advantage of growing new plants from the underground stems like X?

An element A which is a part of common salt and kept under kerosene reacts with another element B of atomic number 17 to give a product C. When an aqueous solution of product C is electrolysed then a compound D is formed and two gases are liberated.

1. What are A and B?
2. Identify C and D.
3. What will be the action of C on litmus solution? Why?
4. State whether element B is a solid, liquid or gas at room temperature.
5. Write formula of the compound formed when element B reacts with an element E having atomic number 5.

A man bought a device X which could cook pulses, vegetables and rice without using any fuel like wood, coal, kerosene or LPG, etc. This device did not work at night. It also took a lot of time for cooking.

1. Name the device X.
2. What is the source of energy which cooks food in this device?
3. What is the name of the process which traps energy in this device?
4. State one advantage (other than saving on fuel) or using such a device for cooking food.

1. Draw magnetic field lines produced around a current carrying straight conductor passing through a cardboard. Name, state and apply the rule to mark the direction of these field lines.
2. How will be strenght of the magnetic field change when the point where magnetic field is to be determined is moved away from the stright wire carrying constant current? Justify your answer.