Chapter 09 : Thermal Processes

Question 1

9.1

thermal equilibrium

Answer 1

it describes the state in which 2 or more objects have the same temperature + no net transfer of energy between them

energy tranfer : from region of higher temperature to region of lower temperature

Question 2

9.2

define thermal conduction

Answer 2

conduction is the process of energy transfer where energy is transferred through the passing on of vibrational motion from 1 particle to another [ medium needed ]

Question 3

9.2

define convection

Answer 3

convection is the process of convection currents of a fluid (liquid/gas), due to a difference in density [ technically needs a medium ]

convection current is formed when hot air rises and cool air sinks

Question 4

9.2

define radiation

Answer 4

radiation is the process of energy transfer by electomagnetic waves. It does not require a medium

radiation from sun is a type of EM wave that can travel through a vaccum at the speed of light

Question 5

qns

what effects rate of radiation?

Answer 5

surface temperaure

surface area

-surface colour & texture

shiny, smooth & light-coloured surface of an object absorbs incoming radiation at a slower rate = emit radiation at a slower rate
matt, rough & dark-coloured surface of an object absorbs incoming radiation at a faster rate = emit raiation at a faster rate

Question 6

qns

define good thermal conductivity

Answer 6

ability to quickly transfer energy from the hotter end to the cooler end

Question 7

qns

how is conduction in solids carried out?

Answer 7

non-metals
1. energy transfered to the rod by heating, particles closer to rod vibrate about more vigourously
2. through collisions, energy is transferred from the more energetic particles to the less energetic particles
3. hence as more energy is tranferred from left to right, the particles here begin to vibrate more vigourously. temperature on other end increases
metals
1. [non-metal process]
+
free electrons heated, gain energy, small size & high speed of electrons allow them to move freely throughout the solid = quickly trasnfer heat from the hotter to cooler side
2. free moving electrons on cooler side are collectively slower after colliding and transferring their energy to coller side, particle vibrate more vigourosuly , temperature increase

Question 8

how does convection occur

Answer 8

when water is heated up, the particles gain heat and slides past one another more faster, resulting in more collisions = farther apart from e/o causing the liquid at the bottom to expand = less dense which rises to the top

while the cooler, more dense liquid sinks to the bottom
the process repeats hence setting up a convection current

Question 9

9.3

how can thermal processes be applied?

Answer 9

conduction
-hair dryer
- instant water heaters
-thermal wear
-double/triple-glazed windows
convection
-electric kettles
-hot ait balloons
-sea breeze
-land breeze
radiation
-greenhouses
-space blanket ( shiny smooth surface )
-global warming ;)