Ask an Expert: Chemistry (2024)

Hello,

ScienceBuddies is for questions related to science fair projects. Are you considering investigating the relationship between salinity and heat capacity for a project?

The speed at which water heats up has to do with its heat capacity. Heat capacity is the amount of heat energy it requires to heat a gram of material one Kelvin degree. The higher the heat capacity the more slowly the water will heat, given the same amount of energy added. The heat capacity of freshwater is 4.182 J/(g K) and the heat capacity of salt water is 3.993 J/(g K). Therefore saltwater will heat up faster than freshwater.

It is important to note that heat capacity is based on the mass of a material, not it's volume. Since salt water is more dense than freshwater comparing how quickly the same volume heats is not equivalent.

Good luck,

Audrey

The above post provides great information, but I would like to expand on it a little. The specific heat of salt water actually depends on its salinity, or its ppm (parts per million). The higher the ppm of the salt water, the lower the specific heat is. The density of salt water increases with increasing ppm, so there is more mass per unit volume. However, if you do some calculations, you'll find that less energy is required to heat salt water with higher ppm even if you're measuring by volume.
Here is a link to a helpful article: http://nexusstem.co.uk/wp-content/uploa ... mies-1.pdf

If you're considering doing an experiment on this topic, the reading the procedure used in the article is a good place to start. However, don't copy their procedure exactly, add your own unique twist on the experiment!