Our main focus for today will be on evaluating a conduction convection radiation worksheet. We shall begin by looking at some common conduction, convection and radiation questions. These questions are;
*Which of the following is not a method a heat transfer?
a)Conduction b)Convection c)Condensation d)Radiation
*Which of the following is the best conductor of heat?
a) air b) ice c)Aluminum d)oil
*The heat transfer method responsible the most for a pot of water to boil
a)Conduction b)Convection c)Radiation d)Boiling
*Which is the best surface for absorbing heat?
a) Shiny White surfaces b)Shiny Black surfaces c)Dull White surfaces d)Shiny Black surfaces
*Fill in the spaces with Conduction, Convection or Radiation.
Causes water to boil.
Involved in frying eggs.
Heat transfer in solids.
Heat transfer in fluids.
Heat transfer with movement in the medium.
Heat transferred by this method is reduced by shiny surfaces.
Heat transferred by this method involves density of fluids.
Is involved when the Sun heats the earth.
Is transferred in the form of waves.
Sodium is a good conductor of heat by this method.
Can travel through a vacuum.
Travels at the speed of light.
It does not require a material to travel through.
*Explain (in terms of radiation, conduction and convection) what happens when cold water in a sealed Aluminum container becomes warm on a sunny day.
*Explain why it is advisable to wear a white shirt rather than a black one on a sunny day.
*On a sunny day, two black bottles of water (one Aluminum and the other plastic) are placed on the roof of a house. After about thirty minutes, the temperatures of the water in both containers are taken and it is noticed that the temperature of that in the Aluminum bottle is warmer. Explain why the water in the Aluminum bottle is warmer than that in the plastic bottle.
A)Conduction: Heat transfer by this method is common in solids especially metals. Here, vibrating atoms gain KE when heated thus transferring it to neighboring atoms, accounting for heat conduction in solids. Metals (like Aluminum or Iron) are very good conductors of heat while Plastics and Rubbers are poor conductors of heat.
B) Convection: Heat transfer by this method usually involves fluids (liquids and Gases). The mechanism involved in this is that warmer air rises and colder air sinks (as cold air is denser than warm air). For example if water is put in a pot which is on a heat source, the water at the bottom of the pot gets warm and rises while that at the top sinks as it is colder and denser. This happens continuously until the water boils.
C) Radiation: This involves heat being transferred in the form of waves. It can travel through a vacuum and through a material. For example, when the sun heats the earth. White or shiny surfaces reflects heat transferred in this form while black or dull surfaces absorbs heat travelling in this form.