Evolution is not based on chance. Let me explain the process.
First evolution is not abiogenesis. I do not know if the first reproducing organism arose by evolutionary processes. I believe in God the Creator. I don't need evolution or the creation of the first molecule to explain life. I believe God created all life. I believe in evolution because nature, God's First Bible, testifies loudly, and in my opinion undeniably, that it is true. On this page, I am only talking about how the first living, single-celled organism, could have evolved into all life today.
There are two processes at work in evolution. One is mutation, which happens purely by chance. The other is selection, which has nothing at all to do with chance. The term “natural selection” was invented by Darwin. He saw that the way farmers produced better cattle and the way dove handlers produced the doves they wanted was by “selecting” animals with the traits they wanted. “Natural selection” then was selected to contrast the “artificial selection” that breeders use.
In artificial selection we have the same two processes. Mutations are produced by chance. If a cow is unusually large or produces an unusually large amount of milk, it may just have happened by chance. However, when the farmers selects the cow for breeding, no chance is involved. The farmer picked that cow on purpose.
It's the same way with natural selection. The mutations that arise are by chance. However, the selection of the mutations are not by chance. If the mutation makes the organism more likely to survive, then it will also be more likely to reproduce and pass its mutations down the line.
Let me explain by using a common anti-evolution illustration. If you were to sit a monkey down at a typewriter and ask it to type out Shakespeare's Hamlet, it would take an almost infinite number of years to produce it by chance. Let's say, though, that you put the monkey on a computer. You have the computer stop when the monkey has typed out the right number of letters. Then the computer saves all the letters that are in the right spot, emptying all the other spots. Then you have the monkey start again, the computer letting it type only into the spots that were wrong before. Again at the end the computer saves all correct letters.
With this method, the monkey is likely to type out Hamlet, or any other work you asked for, in something under 100 attempts, assuming you produced the letters by chance. Evolution is much more like this scenario than the first. Chance mutation produces the “letters,” and selection saves the more effective ones.