The specific heat of water is 4.18 J/(g·°C). How much energy is necessary to raise 15 g of water by 20 °C? (Use the equation Q = m

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1. Answer:

   First thing first, you mistyped the specific heat of water, which should be

   c

   water

   =

   4.18

   J

   g

   ∘

   C

   Now, a substance’s specific heat tells you how much heat is required to increase the temperature of

   1 g

   of that substance by

   1

   ∘

   C

   .

   In the case of water, you would need

   4.18 J

   to increase the temperature of

   1 g

   of water by

   1

   ∘

   C

   .

   Notice that your sample of water has a mass of

   1 g

   as well, which means that the only factor that will determine the amount of heat needed will be the difference in temperature.

   The equation that establishes a relationshop between heat and change in temperature looks like this

   q

   =

   m

   ⋅

   c

   ⋅

   Δ

   T

   , where

   q

   – heat absorbed

   c

   – the specific heat of the substance, in your case of water

   Δ

   T

   – the change in temperature, defined as the difference between the final temperature and the initial temperature

   Plug in your values and solve for

   q

   to get

   q

   =

   1.00

   g

   ⋅

   4.18

   J

   g

   ⋅

   ∘

   C

   ⋅

   (

   83.7

   −

   26.5

   )

   ∘

   C

   q

   =

   239.096 J

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