Tuesday, May 10, 2011

Water has a high specific heat because it has strong __________________.

Water has a high specific heat due to the strong polarity between its bonds.


Specific heat is the amount of heat required to increase the temperature of one gram of a substance by one degree Celsius.


Water is very polar. Polar substances are covalently bonded substances that contain partially positive and negative charges. The partial charges within a polar substance are the result of electronegativity differences between the atoms that share the bond. Electronegativity is the likelihood that an atom will attract a pair of bonded electrons. Amongst all of the elements on the periodic table, electronegativity ranges between approximately 0.7 to 4.0. Some periodic tables contain electronegativity values of each atom. The electronegativity difference between two atoms forming a bond can be used to determine the type of bond that will be formed between the two atoms, as identified below.


Electronegativity differences of less than 0.5 = nonpolar covalent


Electronegativity of 0.5 – 1.6 = polar covalent


Electronegativity difference of 2.0 or more = ionic bond


However, if there is a large electronegativity difference between two atoms but there is symmetry within the compound, then that compound will not display polarity. This is the reason why carbon dioxide (CO2) is not considered to be polar.


Hydrogen has an electronegativity of 2.1 and oxygen has an electronegativity of 3.5. Therefore, the electronegativity difference is 1.4. Thus, water is very polar. The polarity between water compounds results in a type of intermolecular force called a hydrogen bond.


Temperature is a measurement of the average kinetic energy of the particles within a substance. Kinetic energy is the energy of movement. Thus, in order for the temperature of a substance to increase, the particles that make up the substance need to gain kinetic energy and increase in movement.


Water has a high specific heat capacity because the heat added to water is initially used to overcome the hydrogen bonds. It is only when these bonds are broken that the water molecules begin to move freely. It is then that the kinetic energy of the molecules begins to increase, increasing the water’s temperature.

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