Zero conditionals:

If you hear people screaming what do you do?
If there isn't enough food for the guests to eat we can get some Chinese take-away.
I might possibly lend you my mini-scooter if you promise to be careful.
Water boils if you heat it to 100 degrees.
If you cross an international date line, the time changes.
If it rains, the grass gets wet.
Wood doesn't burn if there is no air.

Fiirst conditionals:

I'll be back here by ten p.m. tonight unless the train is late.
If no-one calls by next week I will sell the stereo to you.
What will you do if she refuses to go out with you?
I'll give you the money tomorrow if I can.
As soon as you arrive, I’ll cook dinner.
When I come you’ll be out.
We’ll play tennis, if the rain stops.
If it's sunny, we'll go to the park.
Paula will be sad if Juan leaves.
If you cook the supper, I'll wash the dishes.

When water temperature reaches 100 degrees, this liquid always boils. Когда температура воды достигает 100 градусов, эта жидкость всегда закипает.When Jill eats fish, she is sick. – Когда Джилл ест рыбу, ее подташнивает.One's practice always suffers if one disregards it. Бизнес всегда страдает, если пренебрегать им.Anybody is satisfied if the thing they want to rent looks new. Всякий рад, если вещь, которую он собирается взять в аренду, выглядит как новая.If there's no God, there's no virtue. – Если нет Бога, нет и добродетели.