Acold coke bottle is on the pan of a balance and is left open. what happens to its weight?

It's weight would decrease over time.

Explanation:

The cold coke is going to stabilise in the room temperature. This causes the coke to heat up to room temperature. When the coke heats up, some molecules acquire enough kinetic energy that the evaporate. The evaporation of the molecules causes a decrease in weight.

Hope it helped!

it's weight will decree over time

Explanation:

because the ice will tern to winter than it will evaporate

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000