Snakes belong to a group of animals called reptiles, together with lizards, crocodiles and turtles. Reptiles have dry scaly skin, breathe with lungs, and most lay eggs with leathery shells. They are cold-blooded, which means their body temperature changes with the surroundings, so a snake basks in the morning sun to warm up and hides in the shade at noon. A snake has no legs, no eyelids and no outer ears. It smells by flicking its forked tongue and touching it to a special organ in the roof of its mouth. It cannot hear the snake charmer's flute; it sways because it is following the movement of the pipe.
Of the roughly 300 kinds of snakes in India, only a few are dangerously venomous: the cobra, the krait, the Russell's viper and the saw-scaled viper are known as the big four. A venomous snake has two hollow fangs that inject venom, like a syringe. Venom is used to kill prey, not to attack people, and snakes bite humans only when stepped on or cornered. The only cure for a serious bite is antivenom, a medicine made in hospitals from the venom itself. Thailand also has the king cobra, the longest venomous snake in the world, and many harmless snakes such as the golden tree snake that eat rats and lizards. Snakes are useful to farmers because a single rat snake can eat hundreds of rats that would otherwise destroy grain.
Example: Make a simple thermometer chart. Place two identical jars of water, one in the sun and one in the shade, and measure their temperature every 30 minutes for two hours. Prediction: the sunny jar will warm by several degrees while the shaded jar barely changes. This is exactly how a cold-blooded reptile moves between sun and shade to control its body heat.