What causes pressure inside a helium balloon? A. The helium atoms stick to the surface of the balloon and increase
its weight
B. The helium atoms expand and press on the surface of the balloon.
C. The helium atoms bounce off the surface as they move inside the
balloon.
O D. The helium atoms exert an electrostatic force that pushes the
surface outward.

what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023 

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.

idk what is it? is this a question that you know the answer or u dont