Heat vs Temperature Heat –Form of energy Temperature –Measure of the vibration of molecules –Response to the input or removal of heat

Specific Heat Capacity the heat required to raise the temperature of 1 gram of a substance by 1 o C measured in calories per gram Specific Heat capacity of water = 1 calorie –Higher than most substances water resists changing temperature when heat is added or removed

Table 6-1, p. 123

Latent Heat A change in heat energy that is not detectable as a change temperature Ex: once water reaches 0 o C, a continual removal of heat is required to form ice –Latent heat of freezing –Formation of hydrogen bonds releases heat which must be removed True in reverse…ice absorbs heat as it melts but does not get warmer (latent heat of melting)

Latent Heat also true when going from liquid water to water vapor –Latent heat of vaporization the heat energy is used to break hydrogen bonds –All must be broken to become a gas Opposite=> heat is released when going from gas to liquid= latent heat of condensation

Fig. 6-8, p. 127 Water’s Thermal Properties Affect Climate: Moderate Earth’s Climate

Water Minimizes Day/Night Differences

Density and Temperature Most substances become denser as they get colder density of water increases as water is cooled until a maximum of 1 g/cm 3 is reached at 4 o C

Density and Temperature the density of water drops abruptly as the freezing takes place- hydrogen bonds set up ice is therefore less dense than water –so ice floats

Seawater vs. Pure Water the solids dissolved in seawater change its physical properties they lower the specific heat capacity they lower the freezing point of water density increases until freezing point is reached –ice is pure water & cold, salty water left behind sinks

Dry air descends at the Tropics of Cancer/Capricorn and causes excess evaporation Global Variations in Salinity and Temperature

Variation of Salinity with Depth Excess evaporation at the surface Runoff, ice melting, less evaporation at surface Similar salinity at depth

Variation of Temperature with Depth Cold everywhere Sun warms the surface Cold at depth

Density of Water density is mainly a function of temperature and salinity density increases as temperature decreases density increases as salinity increases colder, saltier water is denser than warm, less salty water

Density Zones in the Ocean 1. Mixed surface layer –temperature and salinity are relatively constant with depth due to waves, currents, winds 2. Upper layer =a middle layer where density changes rapidly with depth –Pycnocline due to thermocline (and sometimes halocline)

Fig. 6-19, p. 136

Density Zones in the Ocean 3. the deep zone –a cold, dense layer on the bottom –average temp =1 to 3 o C –contains the bulk of the world’s ocean (80%)