Foam cup a has 36 ml of water that contains 2 moles of hcl at 20 degrees celsius. foam cup b has 36 ml of water that contains 2 moles of naoh at 20 degrees celsius. the contents of foam cup a are added to foam cup b and a chemical reaction occurs. the final temperature of the contents of cup b is 31 degrees celsius. i need to calculate the enthalpy change of the reaction. the density of both solutions is 1 g/ml.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.