Unit 5. Heat and Light

NATURAL SCIENCE. 5th LEVEL.

UNIT 5: HEAT AND LIGHT. 1. How does thermal energy travel through o!e"ts# Thermal energy always travels from a hotter objet to a ol!er one. C"N#UCTI"N$ %hen two objets are &n ontat' thermal energy &s transferre! from one objet to the other. Th&s (roess &s alle! "ondu"t$on. "ondu"t$on. C"NVEC C"NVECTI" TI"N$ N$ Transfe ransferr of energy energy &nto an! an! o)t of an objet by the movement of fl)&! &s alle! "onve"t$on. "onve"t$on. RA#IATI"N$ Thermal energy an be transferre! thro)gh s(ae by eletromagnet& waves. Th&s (roess &s alle! rad$at$on. rad$at$on. C"N#UC C"N#UCT" T"RS RS AN# INSULA INSULAT T"RS *aislantes+$ Some Some mate mater&a r&als ls are are goo! goo! "ondu"tors. "ondu"tors. Th&s means that they tran transf sfer er ther therma mall ener energy gy eas& eas&ly ly.. "the "therr mate mater& r&al al !on, !on,tt transf transfer er therma thermall energy energy eas&ly eas&ly.. %e all all these these mater& mater&al al thermal $nsulators. $nsulators. %. &hat are the e''e"ts o' thermal energy# Thermal energy a)ses hanges &n the state of some mater&als. -ELT -ELTIN$ IN$ %hen %hen a sol&! sol&! ree&v ree&ves es therma thermall energy energy'' &t hanges &nto a l&/)&!. Th&s (roess &s alle! melt$ng. melt$ng. EVA0"RATI"N$ %hen thermal energy &s a((l&e! to a l&/) l&/)&! &!'' &t han hange ges s &nto &nto a gas. gas. Th&s Th&s (ro (roes ess s &s all alle! e! eva(orat$on. eva(orat$on. E10ANSI"N E10ANSI"N *dilatación+$ Therma Thermall energy energy a)se a)ses s the mole)le mole)les s &n a sol&!' sol&!' l&/)&! or gas to v$rate. v$rate. As a res)lt' the mater&al e2(an!s. C3E-ICAL C3ANES$ Thermal energy an a)se hem&al hanges. ). &hat*s l$ght#. L&ght &s ra!&at&on that we an see w&th o)r eyes. e yes. "bjets reat to l&ght &n !&fferent ways. They an be$ Trans(arent$ Trans(arent$ They !on,t blo4 l&ght. Translu"ent$ Translu"ent$ They They blo blo4 4 some some l&gh l&ght' t' b)t b)t some some l&gh l&ghtt (ass (asses es thro thro)g )gh h the the mater&al. +(a,ue$ +(a,ue$ They blo4 the l&ght om(letely. -. e'le"t$on and re'ra"t$on. e'le"t$on o)rs e'le"t$on o)rs when l&ght energy bo)nes off a s)rfae an! hanges !&ret&on. e'ra"t$on$ e'ra"t$on$ when hen l&g l&ght (as (asses thro thro)g )gh h some tra trans(a ns(are rent nt s)bsta s)bstane nes' s' the l&ght l&ght energy energy hang hanges es !&ret !&ret&on &on sl&gh sl&ghtly tly.. Th&s Th&s (roess &s alle! refrat&on. 

Colour and transformation of light into heat (page 105).