Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 10: Transfer of Heat and its Effects (focus on radiation &…
- Chapter 10: Transfer of Heat and its Effects (focus on radiation & convection)
- Chapter 11 Chemical changes (full) (without acid-metal & acid-carbonate rxn)
- Chapter 12: Interaction within ecosystem TB pg 86-87
Convection
- transfer of thermal energy from one place to another by the physical movement of a medium. fluids (liquids & gases) transfer heat energy mainly by convection.
Convection in Liquids:
- When the water at the bottom of the flask is heated, it expands (particles). The expanded water is less dense than the surrounding water and rises.
- Since the upper region is cooler, it is denser and therefore sinks.
- The difference in the densities of water in the different regions sets up a convection current.
- This is shown by purple streams rising from the bottom and sinking at the sides.
Convection in Gases
- When the air above the candle is heated, it expands.
- The expanded air is less dense than the surrounding air and rises out of chimney B.
- Since the surrounding air is cooler, it is denser and therefore sinks into chimney A.
- The difference in the
densities of the air at the different chimneys sets up a convection current.
-
Ch11: Chemical Changes
- Usually irreversible
- Do not carry same properties as reactants
- Does make a new substance(product)
- Heat, light or mixing involved
- A change in which new substances are formed.
- When a chemical change occurs, it means that a chemical reaction has taken place.
- Reactions in which two or more substances chemically combined to form one or more new substances
-
Physical Changes
- Usually reversible
- Carries same properties as reactants
Radiation
- transfer of thermal energy in the form of electromagnetic waves such as infrared radiation without the aid of a medium. (w/o contact, direct or above)
- All bodies emit infrared radiation.
- Radiation can take place in a vacuum. This is how the Earth is warmed by the Sun.
- The rate of emission of radiation is affected by a few factors.
Factors affecting Emission Rate of Radiation
- Surface area of Object ~ Increase in size of object increases rate of absorption of infrared radiation.
- Colour and Texture ~ Darker Hotter Rougher/ Black & dull surfaces emit infrared radiation at a higher rate.
Applications of heat radiation
- Reducing heat loss/gain
- Solar heaters are painted black to absorb heat quickly from the Sun as black surfaces are good absorbers of heat.