What does below chemistry rebus means?

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

Why despite killing dozens of people Charley and Wilma were not punished?

If two fifty-foot ropes are suspended from a forty-foot ceiling that is twenty feet apart, how much rope will you be able to steal if you have a knife?

what does the below rebus means?

What can go up a chimney down, but can’t go down a chimney up?

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

In this image, you can see three almost identical Doraemon images. Can you spot the odd one out from them?

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?

Can you circle exactly four of these numbers such that the total is twelve?

1 6 1
6 1 6
1 6 1
6 1 6