What is so fragile that saying its name breaks it?

What does below chemistry rebus means?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

Manish and Manoj play 5 games of chess.
Both Manish and Manoj win the exact same number of games. There is no tie at all.

How?

On a beautiful Sunday morning, You ordered a hot tea to your hotel room and suddenly you remember an important thing that needed to be done right now will take around 3 minutes to complete.
Like most people you like your tea to be hot while drinking so, when should you pour cream in the tea?
1. straight away
2. Just people, you drink the team
3. Its does not matter

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

A king sentenced a man to the death sentence for some crime he had committed. Known for his kindness, the king told the culprit that he had a choice to die in a way he decides.

The culprit was clever and said something that saved him from death. What method do you think he must have chosen for his death?

I am sure no one can have two things for dinner. what are they?

What breaks yet never falls, and what falls yet never breaks?