 
 <prompt> Heat dey affect which property wey dey make filament work? Given di last question, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: ```While inert gas dey reduce filament evaporation, e still dey carry heat from the filament, so e dey cool the filament and reduce efficiency. For constant pressure and temperature, the thermal conductivity of gas dey depend on the molecular weight of the gas and the cross sectional area of the gas molecules. Gasses wey get higher molecular weight dey get lower thermal conductivity, because the molecular weight dey high and the cross sectional area dey high too. Xenon gas dey improve efficiency because of im high molecular weight, but e dey cost pass, so dem dey use am small small for lamps.``` 