Calculate the amount of heat required to raise the temperature of an 79 g sample of water from 38 ∘C to 64 ∘C.

Answer 1

We're looking at heat capacity and specific heat of particular materials or compounds. To calculate this we'll use the specific heat formula: q = m c ΔT where q is heat energy, m is mass, c is specific heat constant for the particular material or compound, and ΔT is the change in temperature. The specific heat constant, c, is also described as the heat energy required to raise one mass unit of material up one degree. Temperature will either be in celsius (°C) or in Kelvin for this formula. Units matter here so make sure all of the units are in compliance with each other.

In this case we're looking at the specific heat of water. We have mass in grams and temperatures in degrees celsius so we can look up the specific heat constant of water using in those given units. From a reference table (in a textbook or through a search) we see c = 4.186 J / (gram °C). Again, units matter. Now we can plug in and calculate the heat energy required to raise the temperature:

q = m c ΔT

= (79 g) (4.186 J / g ºC) (64 ºC - 38 ºC)

= 8598.044 J

= 8598 J (if rounding for significant digits)