How to use As long as and unless

As long as

Take a look at this sentence:

"I will go if it is free."

(If it is free, I will go.)

In this sentence we can change if to as long as and it keeps the same meaning:

"I will go as long as it is free."

(As long as it is free, I will go)

Here are some other examples:

"You can borrow my bike as long as you are careful." = You can borrow my bike if you are careful.

"You will pass the test as long as you study hard." = You will pass the test if you study hard.

I will go there as long as it's free!
Unless it is free, I won't go there!

Unless

Now let's look at the same if sentence using a negative:

"If it isn't free, I won't go."

(I won't go if it isn't free.)

Here we can use unless to keep the same meaning:

"Unless it is free, I won't go."

(I won't go unless it is free.)

Unless means except if or only if.

Here are some other examples:

"I'll walk to town unless it rains." = If it doesn't rain, I'll walk to town.

"Unless we leave now, we’ll be late." = If we don't leave now, we'll be late.

"You can't enter unless you have a ticket." = Only if you have a ticket, can you enter.