allthebest Posted May 1, 2016 Report Share Posted May 1, 2016 A pure aluminium block with a mass of 10 g is heated so that its temperature increases from 20 °C to 50 °C . The specific heat capacity of aluminium is 8.99 × 10–1 J g–1 K–1. Which expression gives the heat energy change in kJ? A. 10 × 8.99 × 10–1 × 303 B. 10 × 8.99 × 10–1 × 30 C. ( 10 × 8.99 × 10–1 × 303) / 1000 D. ( 10 × 8.99 × 10–1 × 30) / 1000 The answer key says its D. I thought it was C. Why is it D? using the formula q=mc∆T the ∆T will be 50-20 = 30 'C and change to Kelvin so 273+30 = 303K so isn't it 10 x 10 × 8.99 × 10–1 × 303 J and to change it to kJ I need to divide by 1000? Since the specific heat capacity is given in K shouldn't I use Kelvin? Please answer this asap Thank you!! Reply Link to post Share on other sites More sharing options...
eross Posted May 1, 2016 Report Share Posted May 1, 2016 Hi! Yes, you need to calculate the change in temp in kelvin, but that's what you did wrong 20 C = 293 K and 50 C= 323 K So change in temp = 323-293 =30 K. You might have noticed that this is the same as doing 50 C-20 C; the CHANGE in temperature in Kelvin is the same as the change in temperature in Celsius (very important to remember that this only applies to change in temperatures) I hope this helped clarify your doubt 1 Reply Link to post Share on other sites More sharing options...
allthebest Posted May 1, 2016 Author Report Share Posted May 1, 2016 @eross thank you very much!! It helped clarify my question. Reply Link to post Share on other sites More sharing options...
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