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 a crumple zone on a car reduces injury to the driver in a crash.
A runner of weight 588N runs at a speed of 8 miles/hr. What is the kinetic energy of the runner? Determine the power exerted by the runner over a distance of 10m.
Explain the process of nuclear fusion in the Sun.
Write down the equation which links speed, distance and time