thermoregulation

Question 1

boiling point

Answer 1

VP = Patm

only Temp at which a liquid and a vapour can coexist in equilibrium for a given pressure.

Question 2

specific Latent Heat of Fusion

Answer 2

energy required to convert 1kg of liquid to 1 kg of gas ( at the same T)

Question 3

Latent Heat of Vapourisation - Lv

Answer 3

applied to change liquid to gas

Question 4

Specific Latent Heat of Fusion -Lf

Answer 4

energy required to convert 1kg of solid to 1 kg of liquid ( at the same T)

Question 5

how does the body cool itself

Answer 5

Body cools itself by stealing LV to evaporate sweat on skin.

Question 7

phase diagram

Answer 7

Temp at which phase change occurs, varies with the absolute pressure

point A=Triple Point and characterises the only conditions under which all three phases (solid, liquid & gas) can exist simultaneously.

positive “slope” of the liquid-gas phase boundary of the H2O Phase Diagram.

Can boil water at T< 100oC if the gas pressure above the liquid surface is lowered

conversley if the fluid pressure increases, the Boiling Point increases

H2O is unusual in that the phase boundary between solid and liquid has negative slope. This means that the freezing (or melting) point Temp increases as pressure is reduced.

Question 8

charles law

Answer 8

gas law that describes how gases tend to expand when heated

Question 9

Sublimation

Answer 9

water freeze at temperatures > 0oC if we reduce the air pressure

so

if pressure reduces sufficiently we can skip the liquid phase completely and go straight from solid to gas phase

eg dry ice

Question 10

Bose-Einstein Condensate (BEC)

Answer 10

with a Quantum Mechanical state caused from removl of nearly all the heat energy from a small group of inert atoms

Question 11

temperature

Answer 11

property of an object that determines the direction of heat flow when it is brought into thermal contact with another object.

Heat ALWAYS flows from high T to low T.

Question 12

heat

Answer 12

form of energy that is transferred between systems or objects with different temperatures

Question 13

Temperature Scales

Answer 13

SI scale is Kelvin (K) but typically use Celsius oC scale

Rankine Scale = Fahrenheit (oF) version of K (°R = °F + 459.67)

Question 14

thermometric property

Answer 14

All thermometers use a thermometric property of a substance.

property of a substance that changes in a uniform ( but not necessarily, linear relationship) and predictable manner as T changes.

Question 15

body temp and factors that effect it

Answer 15

core temp = 37

Oral Cavity 0.4oC lower than core T = 36.6

-time of day, age , hard work, emotions

Axilla (arm-pit) 0.9oC lower than core T= 36.1

Rectum 0.3oC higher than core= 37.3

• hard exersise, emotion

menstraul cycle, durinal cycle

Question 16

change in temp

Answer 16

To change Temp of an object, heat energy must be either added or removed.

If a quantity of heat Q is added, the rise in T depends on mass and the Specific Heat Capacity (C).

Question 17

Specific Heat Capacity

Answer 17

amount of heat energy required to change the temperature of 1kg of a substance by 1 degree Kelvin. C has units of J kg-1 K-1

amount of heat (Q) needed to cause a change in temp /\T in a mass m is:

Question 18

heat transfer

Answer 18

Heat flows from hot to cold by 3 methods:

• Conduction (solids)

Convection (liquids & gases)

Radiation (vacuum)

Question 19

conduction

Answer 19

air is a cood insulator

Question 20

convection

Answer 20

Heated fluid (liquid or gas) becomes less dense and rises up, away from heat source. The cooler, denser fluid sinks to replace it.

causes wind chill

Question 21

radiation

Answer 21

Doesn’t need a physical link between heating and heated objects. Can occur across a vacuum

Question 22

Thermoregulation

Answer 22

strategies to maintain body T in a constantly changing temperature environment.

Question 23

thermoregulatory responses when outside temp is very low

Answer 23

(a) Counter Current Exchange
- Heat lost by outgoing arterial blood re-heats returning veinous blood & minimises heat loss in limbs
- exchange minimises conductive & radiative heat loss

eg mechanism for keeping testes at optimum temp. for producing healthy sperm which is 3-4oC lower than normal body temp.

• As body temp increases, the cremaster and dartos muscles relax. This lowers the scrotum further away from the body and increases the effective length of the veinous pampiniform plexus.

increased cooling in facilitated by larger scrotal surface area

minimizes total heat loss from the blood via counter-current exchange by passing it through the pampiniform plexus.

B)Piloerection - vestigial response : goosebumps: hair stands up Tries to trap a layer of air.

(c) Vasoconstriction;Veinous flow near skin reduces with T.
- Accomplished with shunts and sphincters

eg

Blood flow thru sub-cutaneous capillary networks is controlled
by sphincter muscles and shunts

d) shivering :•involuntary muscle spasms.

55% of metabolic activity is lost as heat. Heat energy released during metabolic activity is used to warm the body.

Question 24

thermoregulatory responses when body is too warm

Answer 24

a) vasodilation causes sub-cutaneous capillaries to fill with blood, giving a “flushed/rosey cheeked” appearance when hot.
(b) Sweating (perspiration) steals Latent Heat of Vapourization from the skin to form vapour and the loss of heat energy cools the body.