What does below chemistry rebus means?

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 miles long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 mph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

In the image given, you can find several triangles. Can you count them all?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

What does this rebus mean?

O
N
C
E
TIME

Can you find the thief by just looking at the picture below?

A clock loses 10 minutes each hour. If the clock is set correctly at noon, what time is it when it reads 3 PM?

Why is the longest human nose just 11 inches?