SMS 204: Physics for marine sciences ��Heat and Temperature

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• Instructor: E. Boss.

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Heat and temperature

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Temperature- proportional to microscopic kinetic energy of matter.

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If two objects (systems) have the same temperature they will stay the same upon contact (1^st law of thermodynamics).

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If they have different temperatures heat (energy) will be transferred (hot🡪cold).

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T

• Measuring temperature

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Find materials whose physical properties you

measure (X, e.g. volume) varies linearly with temperature (T):

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X=aT+b

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Demo: water thermometer

Latent and sensible heat

• Sensible heat: changes temperature but not state.

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• Latent heat: chages state but not temperature.

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Heat and temperature

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Heat- microscopic kinetic + potential energy of matter. When we change the state of a material we need to provide heat.

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To warm a mass of material by ΔT we need to supply it with heat (energy):

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Sensible heat = C_p × Mass × ΔT

[M L² T^-2] = [L² T^-2 K^-1] × [M] × [K]

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C_p-specific heat capacity

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For water 1calorie (=4.184 joules) heats 1gr of water one degree at STP. For air ~1 joule.

• Heat and temperature

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Why do we sweat? Why do dogs have a wet nose? Do we feel a different temperature on a humid day (Heat index, wind chill)?

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Ocean vs. atmosphere, which gets cooled which gets heated in different parts of the hydrologic cycle?

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Energy, heat content in food:

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1 Calorie = 1000 calories= 4184J, energy to heat ~1 liter by 1°C, evaporate ~2gr of water at 100°C or melt ~50gr of water at 0°C.

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Q: does evaporation only occur at 100°C ?

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A Hershey kiss (26 Calories) could provide the energy to lift an SUV 2m off the ground. 🡨 extra credit

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Food webs are not very efficient. Only a small percentage of the energy available in the food is effectively transferred into biomass.

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Ocean vs. atmosphere, which gets cooled which gets heated in different parts of the hydrological cycle?

Source: NCAR

Principal modes of heat transfer:

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SMS 204: Integrated marine sciences

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1. Radiation (E/M radiation travel through space absorbed).

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2. Conduction (objects touch).

3. Convection/advection (fluid motion transfers heat).

Radiative heat flux:

Bodies radiates energy according to their temperature (humans, 311K, radiation at 10μm,

Radiates about 2,000Kcal day^-1).

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Earth/oceans:

Short wave heat flux

Long wave heat flux

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Demo - radiation

Convective heat flux:

The fluid density is temperature dependent.

Along path, horizontal advective heat flux may be important.

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Demo - convection

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Convection and advection

Heat conduction:

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Heat flux = -KΔT/Δx

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K-heat diffusion coefficient

Examples:

Ice, Fur, Blubber

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Heat flux, recap:

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latent heat flux

sensible heat flux

radiative heat flux

advective heat flux

• The heat balance of the Earth:

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The ‘greenhouse’ effect:

Water vs. air

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Density: 1.2 vs. 1000 kg m^-3

C_p: 1 Jg^-1K^-1 vs. 4.2 Jg^-1K^-1

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Heat content:

Atmosphere ~ 2.5m of ocean

Water vs. land

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Density: 2500 vs. 1000 kg m^-3

C_p: 1 Jg^-1K^-1 vs. 4.2 Jg^-1K^-1

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Difference in how heat is acquired

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1. When are the longest/shortest day of the year?

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2. When are the hottest/coldest days of the year?

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3. How is ocean heating/cooling different from land?

Temperature profiles in lakes and the ocean.��1. What should we expect?�2. Where is warming occurring?�Cooling?�3.How is heat transferred in the interior?

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How does T affect biology?

• How do organisms lose/gain heat?
• Cold/warm blooded organisms
• Enzymatic reactions as f(T)
• Swimming & brain performance
• Heat and size (area/volume ratio)
• Wind chill?
• Hypothermia
• Viscosity as f(T)

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