Thermodynamics

Second law of Thermodynamics

• The Second Law actually states that the total entropy of a closed system (one where no energy or matter can leave/enter) cannot decrease.
• More important, however, the Second Law permits parts of a system to decrease in entropy as long as other parts experience an offsetting increase.
  • Thus, our planet as a whole can grow more complex because the sun pours heat and light onto it, and the greater entropy associated with the sun's nuclear fusion more than rebalances the scales. Simple organisms can fuel their rise toward complexity by consuming other forms of life and nonliving materials.

Boiling

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid. At this point, water turns into a vapor.

Boiling happens when water molecules have enough energy to spread out and form bubbles. These bubbles rise to the surface and release water vapor.

• When we increase the air pressure around the water, we are putting literally more pressure on these molecules, and it becomes more difficult for them to spread out. Therefore, the threshold of boiling increases.
• When we decrease the air pressure, it's easier for these molecules to spread out, which is our definition of Boiling
• water only boils at 100 °C at sea level. At 1900m of altitude, the boiling point is 93.4 °C.

Therefore, boiling of a liquid depends on the atmosphere surrounding it (Ex. Earth, an enclosed container)

Ex. When you push water in a syringe, the air bubble will get smaller as we make the chamber smaller. This shows that as pressure increases, water molecules are getting closer together, and the boiling temperature threshold will rise.

Pressure makes it difficult for boiling to take place, which is why water boils in a vacuum: It's not that vacuums cause water to boil, it's that less pressure results in easier conditions under which water can boil (ie. lower temperatures)

• as a result, water boils at a lower temperature at higher altitudes: there is less atmospheric pressure to get in the way of boiling

Atmosphere

As you go higher in the earth's atmosphere, there is less pressure due to the fact that there are fewer air molecules

• air has mass, which is why there are more air molecules closer to the earth. This is also why the atmosphere doesn't drift into outer space

The weight of the air above us pushes down due to gravity, creating atmospheric pressure