Hash is not pure THC, it is heavily concentrated, but to make the hash you have to add some roughage back in, usually ground up plant.

As for eating ... that's all we used to do. A gram will mess you up pretty good. Don't be fooled by how long it takes to enter your system, once it's there you will suddenly become VERY high. I've seen people fall out of their chairs.

Save some to smoke while your waiting for it to be absorbed into the system, a process that can take an hour or two.