Why, in a thermal flask, does having a vacuum layer help keep the coffee warm?
Heat is transferred by 3 processes, conducation, convection and radiation. Having a vacuum layer stops heat being transferred away from the coffee by conduction. Conduction works by air molecules bumping into eachother and transferring some of the energy they have, therefore if you remove the air then you stop energy/heat being taken away in this way which helps keep the coffee warmer for longer.
BO
Related Physics GCSE answers
All answers ▸Describe how the forces change on a parachutist while they fall.
Why is the nuclear model better than the plum pudding model of the atom?
If Hannah slows down from a speed of 12 m/s to 8 m/s and has a mass of 45kg, how much force has been exerted on her to cause this deceleration?
What is meant by the conservation of energy?