Carbon and its Compounds — Science STD 10 — Question

Give any two ways in which non-biodegradable substances would affect the environment.

Define kilowatt-hour. How many joules are there in one kilowatt-hour?

How do metals react with hydrogen? Explain with an example.

Which of the following are conductors and which are insulators? Sulphur, Silver, Copper, Cotton, Aluminium, Air, Nichrome, Graphite, Paper, Porcelain, Mercury, Mica, Bakelite, Polythene, Manganin.

What is meant by ‘unisexual flowers’ and ‘bisexual flowers’ ? Give two examples of each.

What happens when zinc granules are heated with sodium hydroxide solution?
Write equation of the reaction which takes place.

To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.

1. In which direction-towards or away from the lens does he move the screen to focus the object?
2. How does the size of image change?
3. Approximately at what distance does he obtain the image of magnification -1?
4. How does the intensity of image change as the object moves farther and farther away from the lens?

A person needs a lens of power, -5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power, +1.5 dioptres. What is the focal length of the lens required for correcting

1. Distant vision, and
2. Near vision?

How does use of a fuse wire protect electrical appliances?

A child has drawn the electric circuit to study Ohm’s law as shown in Figure. His teacher told that the circuit diagram needs correction. Study the circuit diagram and redraw it after making all corrections.