Energy Transfer

Question 1

Complete the sentence. All objects_____ and _____ infrared radiation.

Answer 1

All objects ABSORB and EMIT infrared radiation.

Question 2

True or False? The hotter an object is the more infrared radiation it radiates in a given time.

Answer 2

True

Question 3

Describe the different types of surfaces and their ability to absorb/emit radiation.

Answer 3

Dark, matt surfaces are good absorbers and good emitters of infrared radiation. Light, shiny surfaces are poor absorbers and poor emitters of infrared radiation. Light, shiny surfaces are good reflectors of infrared radiation.

Question 4

Which out of the three diagrams below represents the arrangement of particles in a solid, liquid or gas.

Answer 4

A= Gas B= Liquid C= Solid

Question 5

Metals are good conductors of thermal energy (heat energy). Explain why this is in terms of the structure of the metal.

Answer 5

Metals conduct heat very well because of the fact that the electrons are free to move inside the metal. At the hot end the electrons move faster and collide with other free electrons, transferring energy. These other electrons then pass on their extra energy to other electrons. Due to the fact that the electrons can move freely, this is a much faster way of transferring the energy through the metal.

Question 6

What is the definition of conduction?

Answer 6

Conduction of heat energy is the process where vibratiing particles pass on their extra kinetic energy to neighbouring particles

Question 7

What is the most important thing to remember about convection currents?

Answer 7

They are all about changes in density. Less dense water rises and more dense water sinks.

Question 8

What is condensation?

Answer 8

When gas turns to a liquid.

Question 9

When can evaporation occur?

Answer 9

• When the particles are travelling in the right direction to be able to escape
• When the particles are moving fast enough to overcome the attractive forces of the other particles in the liquid

Question 10

Which factors speed up the rate of evaporation?

Answer 10

• The temperature- higher temperature means more energy which is quicker
• The density- lower density means weaker forces of attraction
• Surface area- larger surface area means quicker rate of evaporation

Question 11

Which factors speed up the rate of condenstation?

Answer 11

• The temperature of the gas- the lower the temperature the faster the rate of condensation
• The temperature of the surface that the gas touches- the lower the temperature of the surface the faster the rate of condensation
• The density- the higher the density the stronger the forces of attraction between the particles.

Question 12

How is the vacuum flask designed to limit heat transfer?

Answer 12

1. The glass bottle is double-walled with a vacuum between the two walls. This stops CONDUCTION and CONVECTION through the sides.
2. The walls either side of the vacuum are silvered to reduce heat loss by RADIATION.
3. The bottle is made with a layer of insulating foam. This limits heat lost be CONDUCTION because foam is a bad conductor.
4. The stopper is amde of plastic and filled with cork. Both of these are bad conductors so it reduces CONDUCTION.