7. 1 point
The cooling curve below represents the uniform cooling of a substance, starting at a temperature above its boiling point.

During which time interval does the substance exist as both a liquid and a solid?

(1) min 2 to min 4

(2) min 4 to min 5

(3) min 5 to min 7

(4) min 7 to min 9

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."

1. they vary with a higher number because boiling is way hotter than melting

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.