Chapter 14 - Energy Transfer by Heating Flashcards
What is conduction by energy caused by in a metal?
Free electrons transferring energy inside the metal
Why are non-metals poor conductors?
Don’t contain free electrons
What happens to the free electrons in conduction?
They gain KE and increase in speed. Then spread out and collide with other free electrons. Transfer free KE to other ions and electrons
Why is there a smoother energy transfer in metals (conduction)
Electrons aren’t held inside atoms
Define convection
Circulation of a fluid caused by heating it
What happens to a liquid when you heat it?
Becomes less dense and rises
Why do fluids rise when heated?
They expand, volume increases and density decreases
Define evapouration
When a liquid turns into a gas
Define condesation
When a gas turns into a liquid
What causes a liquid to cool down?
Faster moving particles escaping the liquid
How can you increase the rate of evaporation?
Increasing the SA, Temp or creating a draft of air over the liquid
How can you increase the rate of condensation?
Increasing the SA or lowering the temp of the surface
What is infrared radiation?
Energy transfer by EM waves
Do all objects emit infrared radiation?
Yes
What happens to the infrared radiation if you increase the objects temp?
The rate increases over time
Do all objects absorb infrared radiation?
Yes
What properties must an object have to emit more infrared radiation?
Dark, Matt
What properties must an object have to emit less infrared radiation?
Light, shiny
What properties must an object have to absorb more infrared radiation?
Dark, matt
What properties must an object have absorb less infrared radiation?
Light, shiny
What happens to radiation reflected from dark, matt surfaces?
Hit the surface again
What happens to radiation reflected from light shiny surfaces?
Travels away from the surface
What does the rate of energy transfer depend on?
Shape, size, material, nature of surface, temp difference
How does a vacuum flask keep the temp of a drink inside it hot?
Cuts out a lot of conduction, convection, evaporation and radiation
What cuts down conduction in a vacuum flask?
Vacuum between 2 walls, Glass is a poor conductor,
What cuts down convection in a vacuum flask?
Vacuum between 2 walls,
What cuts down evaporation in a vacuum flask?
Plastic cap
What cuts down radiation in a vacuum flash?
Light, silvery surfaces
What is true about the expansion of gases and solids and liquids?
Gases expand much more when heated
Name an application of expansion of heating
Thermometers and thermostats containing liquid
What do all buildings and bridges need to have?
Expansion gaps
