Life Processes — Science STD 10 — Question

Give the general formula of an:

1. Alkane.
2. Alkene.
3. Alkyne.

What chemical properties of elements were used by Mendeleev in creating his periodic table?

How does the valency of elements vary (i) in going down a group, and (ii) in going from left to right in a period of the periodic table?

List two observations which you make when you add a pinch of sodium hydrogen carbonate to acetic acid in a test tube. Write chemical equation for the reaction that occurs.

Complete the following statements:
When the sun is setting, the light from it has to travel a ____ thickness of the earth's atmosphere and only ____ wavelength _____ light is able to reach us. Sunset is therefore ___.

What is the maximum power in kilowatts of the appliance that can be connected safely to a 13A, 230V mains socket?

What are the characteristics of energy transfer in biosphere?

Among animals, the predators (like lions) have their eyes facing forward at the front of their heads, whereas the animals of prey (like rabbit) usually have eyes at the sides of their head. Why is this so?

The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?

What is spectrum? What is the name of glass shape used to produce a spectrum?