Specific Heat CapacityWeather Unit – Science 10

• Specific Heat Capacity can be thought of as a measure of how much energy (in the form of heat) is needed to warm the substance up.

• Consider This: Water has a relatively large heat capacity. It takes a lot of energy to raise the temperature of water. This means that unlike other substances, water can absorb a lot of the sun’s energy and it will not change it’s temperature dramatically.

• This also means that it loses energy relatively slow as well. • Water’s high heat capacity allows it to moderate temperature.

(Think about the graphing activity you did)

• Specific Heat Capacity (C) of a substance is the amount of heat required to raise the temperature of 1g of the substance by 1oC.

• The units of specific heat capacity are J oC-1 g-1. Sometimes the mass is expressed in kg so the units could also be J oC-1 g-1 or J C-1 kg-1

• J = Joules, kJ = Kilojoules • C = Degrees Celsius• g/Kg = Grams or Kilograms

The amount of heat energy (Q) gained or lost by a substance = mass of substance (m) X specific heat capacity (C) X change in temperature ( T, TΔ 2 – T1)

Q = m x C x T Δ

The Equation

• The table shows how much energy it takes to heat up some different substances.

• The small values show that not a lot of energy is needed to produce a temperature change, whereas the large values indicate a lot more energy is needed.

How much energy would be needed to heat 450 grams of copper metal from a temperature of 25.0ºC to a temperature of 75.0ºC? (The specific heat of copper at 25.0ºC is 0.385 J/g ºC.)

Example #1

Solution:

The change in temperature ( T) Δ is:

75ºC - 25ºC = 50ºC

Given mass, two temperatures, and a specific heat capacity, you have enough values to plug into the specific heat equation

Q = m x C x T Δ

and plugging in your values you get

Q = (450 g) x (0.385 J/g ºC) x (50.0ºC)

= 8700 J

Examples

1. What quantity of heat is required to raise the temperature of 450 grams of water from 15°C to 85°C?

2. Calculate the specific heat capacity of copper given that 204.75J of energy raises the temperature of 15g of copper from 25°C to 60°C

3. 216J of energy is required to raise the temperature of aluminum from 15°C to 35°C. Calculate the mass of aluminum. (C = 0.90 J/°C x g)

Websites For Practice

• http://www.algebralab.org/practice/practice.aspx?file=Algebra_SpecificHeatCapacity.xml

• http://www.kentchemistry.com/links/Energy/SpecificHeat.htm