Science chapter 10

• Temperature is the degree of how cold or hot something is
• The SI unit of thermal energy is Joules
• Mass remains constant when an object is heated
• Density decreases when an object is heated
• Gas expands the most when heated due to its weak forces of attraction
• Heat can be transferred through conduction, convection and radiation
• Conduction is the transfer of heat without movement of the medium and through the movement of particles
• Metals gain heat faster than non-metals due to the process of electron diffusion and the free electrons
• Solids are better thermal conductors because its particles are close together
• Convection is the transfer of heat through the circulation of fluids due to a density difference
• The denser fluid rises up and the less dense fluid flows in to take its place. This process repeats and a convection current is created
• Radiation is the transfer of heat without a medium and through electromagnetic waves like infrared waves
• Factors affecting the rate of radiation includes: Nature of surface, surface temperature of radiator, surface area of radiator
• Dark and rough surfaces are good absorbers and emitters of thermal energy by radiation while shiny and smooth surfaces are poor absorbers and emitters of thermal energy by radiation
• Dark and rough surfaces are poor reflectors of thermal energy while shiny and smooth surfaces are good reflectors of thermal energy
• The bigger the surface area of radiator, the higher the rate of radiation
• The higher the surface temperature of radiator, the higher the rate of radiation
• Caps in vacuum flask are made of materials that are poor conductors of thermal energy to minimize heat loss by conduction
• Stoppers in vacuum flask are made of materials that are poor conductors of thermal energy to minimize heat loss by conduction
• Stoppers in vacuum flask seals the inside of the flask from other surrounding air, preventing the air from entering the flask and creating a convection current that constantly gains heat from the contents. Thus, reduces heat loss by convection.
• Double silvered glass walls in vacuum flask are painted silver which is a good reflector of thermal energy, thus reducing heat loss by radiation
• Double silvered glass walls in vacuum flasks are made of glass which is a poor conductor of thermal energy, thus reducing heat loss by conduction
• Vacuum in vacuum flasks prevents heat loss by convection and conduction since they both need a medium to occur
• Air trapped between double-glazing windows is a poor conductor of thermal energy, thus reducing heat loss or gain by conduction