If venomous snakes evolved then how does the snake become aware that it has venom inside it?

Why would it be aware. Things happen inside your body that make it work. You aren't aware of what they are unless you read a science book written by people who cut people open and looked and studied it. It works but I'm sure most snakes aren't aware of it.

Of course snakes don't go round saying to themselves, "oh great I'm venomous". How would a snake have a vocabulary that included "venomous"?

However, i was wondering, do they die if they accidentally bite their own tongues?

Those who were not aware of it died out more often those who were aware took that to their advantage, lived, and spread their genes on.

It does not need to be aware. It is the same as when you were an infant. You did not need to know that when a nipple or teat was placed in your mouth you should suck in order to get milk and therefore nutrients you just did it. Likewise you did not need to know how to or why to defecate and urinate. You just did.

Snakes do not have to know what they are doing. It is all instinctive. A baby snake is born with all the instincts it needs. It does not have to know or learn. Natural selection shapes the behavior of organisms. Instincts are hardwired into the nervous system. One neuron fires after another in a predetermined sequence and instinctive behavior (such as the knee jerk reaction or the vomiting response in humans) cannot be altered or stopped once it is triggered. Try this if you do not believe me. Gag yourself to start vomiting and then try to stop yourself from vomiting. You will find that you cannot do it.

Snakes evolve venom by modifying the Duvernoy's gland. Non-venomous snakes have a Duvernoy's gland in the mouth, but venomous snakes have a venom gland but no Duvernoy's gland. When a non-venomous snake catches food, it will clamp down on its prey. Some non-venomous snakes will then pin down its prey with its body and then try to swallow the animal alive. Some of them would wrap the prey with its body and suffocate the prey before swallowing starts.

Scientists think that snakes first evolved venom by modifying the rear fangs. Rear fanged snakes will chew the animal after grabbing it with the rear teeth, which are enlarged in rear fanged snakes. These teeth often have grooves on the outside of the teeth so the venom or toxic digestive secretions can flow easily into the prey and enter its body through the openings created by the rear fang. Rear fanged snakes therefore already behave differently than non-venomous snakes. How do they "know" they should behave differently? The answer is that they really do not know. It is instinctive. For example, if a snake starts to chew its prey because there is a mutation that changes its instinctive behavior of simply holding on and if that change in behavior is advantageous, and it is more successful in feeding, then natural selection will increase the frequency of this mutation within the population and my be even the entire species through many generations. Further, additional mutations, such as grooves on the teeth because of another mutation will make the descendants of these snakes more fit (better able to survive and reproduce), and the grooves will become the norm.

Scientists think that venomous snakes with fangs in the front evolved from rear fanged venomous snakes. That means the rear fangs moved to the front through a mutation in the developmental genes. Because there is less room in the front of the mouth for fangs, many venomous snakes have short fangs. Some, called vipers, have evolved long fangs by making them movable so that the fangs can be folded and stored when not in use. Fangs that are folded are not as strong and may break more easily. Longer fangs also allow the snake to inject venom deeper into the body, increasing success rate of killing prey. Longer but weaker fangs that can kill more easily do not require a snake to hang on to its prey. So, the vipers modified its behavior, through mutation, by letting go of its prey after injecting venom. It is all instinct. Non-venomous snakes would never release their prey the way venomous snakes do, because such behavior would not be advantageous and a snake that has the wrong instincts will simply be weeded out by natural selection.

A reptile's brain is not capable of anything like continuous knowledge. A reptile is not aware that it has a heart, but that doesn't prevent its heart from functioning. Same with its venom.

So what you're saying is a erection isn't evolvement wanting involvement ?

FYI, your question was accidentally posted to the Religion And Spirituality instead of the Biology section. I'd move it for you but I am not level 7 and do not have that capability.

Probably because it's naturally aware that it can use venom against other animals.

Evidently the awareness evolved too. Still waiting to see a fundie post an intelligent question about evolution, which is a LONG established fact.