Control and Coordination — Science STD 10 — Question

Non-metals do not evolve hydrogen gas when react with water, steam or dilute acids. Why?

A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine. Support your answer with reason.

If you could use any source of energy for heating your food, which one would you use and why?

What is meant by a renewable source of energy? Give two examples of renewable sources of energy.

A person walking in a dark corridor enters into a brightly lit room:

1. State the effect on the pupil of the eye.
2. How does this affect the amount of light entering the eye?

1. If you are asked to report your observations about the following two properties of acetic acid, what would you report?

1. Odour.
2. Effect on litmus.

2. If you take a pinch of sodium hydrogen carbonate powder in a test-tube and add drop-by-drop acetic acid to it, what would you observe immediately? List any two main observations.

Two circular coils A and B are placed close to each other. If the current in coil A is changed, will some current be induced in the coil B? Give reason for your answer.

Why is graphite a good conductor of electricity but diamond is a non-conductor of electricity?

How do the properties of eka - aluminium element predicted by Mendeleev compare with the actual properties of gallium element? Explain your answer.

Write down a formula for the magnification produced by a concave mirror.

1. In terms of height of object and height of image.
2. In terms of object distance and image distance.