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Course: Biology library>Unit 3

Lesson 3: Temperature and state changes in water

Specific heat of water

Specific heat of water. A calorie as the specific heat of water. How water moderates temperature.

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• If the reason things are hot is because things are vibrating then why do we blow on things like food to cool them down? Wouldn't that just make them vibrate more, therefore becoming hotter?
• When you blow on your tea you're blowing away all the hot steam on top, thus preventing it from being further heated.
• So does it also mean that the 500 kilocalorie bowl of ice cream has the energy to bring one gram of water up 500,000˚ C?
• No. The properties would change as the water heated and the water would eventually break into its constituent atoms.
It is more accurate to say that 500 kilocalories is 500 times the energy required to raise 1 kg of liquid water from 14.5°C to 15.5 °C.
However, because of the difficulty of measuring this amount of energy due to the properties of water changing with temperature, pressure, and purity of the water, nowadays the calorie (not kilocalorie) is usually defined to be 4.1868 Joules.
• So, how is it possible that sand has a lower specific heat than water, when sand is thicker?
• "Thickness" (density?) has nothing to do with energy capacity. Some forms of rubber and plastic are very dense but still have lower specific heat.
• what substance has the lowest specific heat?

- nate ;D
• found this online : Technetium having the lowest heat capacity at 63 J/(Kg K)

Hydrogen has the highest heat capacity with 14300 J/(Kg K)

hope this helps :D
• I don't know what Celsius actually means. I do know that it is a form of temperature. Does any one else know?
• Celsius, also known as centigrade, is the primary temperature scale used throughout most of the world except the USA and a very few smaller countries. In the Celsius scale, the freezing point of water is 0°C and the boiling point is about 100°C (at standard pressure).

In science, we use Celsius or Kelvin. Fahrenheit is almost never used in science.
• I'm not sure I understand this, so basically, water has a higher specific heat because the bonds between the oxygen and hydrogen are more temporary than the molecules in sand?
• Water has a higher specific heat capacity because of the strength of the hydrogen bonds. It requires a significant of energy to separate these bonds. Sand is comprised of metals and pyroxene (silicates [molecules with a SiO4 anion] that commonly contain Ca, Fe, and/or Mg), which are comprised of weaker covalent bonds.

So in conclusion, water has a higher specific heat capacity than sand because water's hydrogen bonds require a lot more energy to break than the covalent bonds in the sand particles.
• If sand molecules are more polar than water molecules, shouldn't it take more heat to break up those bonds and cause the molecules to vibrate, resulting in a higher specific heat for sand than water?
• Why do we avoid eating too many calories then? If the water in our body simply heats up, then why do we refrain from having foods containing higher calories?
• One thing to clarify: we don't really avoid eating calories, we avoid eating too many calories. We need calories to live, but too many is not a good thing. Think about vitamins: they are essential to life but it is dangerous to take too many vitamins. This is similar to calories.