<span>The best reason I can think of for why we believe that air is a mixture is that freezing air slowly yields different liquids at different temperatures. Liquid nitrogen has a different boiling point than liquid oxygen. They also freeze at different temperatures. If air were only 1 compound, then air in its entirety would have a single boiling point and a single freezing point. </span>
Answer:
The answer is
<h2>219.5 mL</h2>
Explanation:
The volume of a substance when given the density and mass can be found by using the formula

From the question
mass = 4500 g
density = 20.5 g/cm³
We have

We have the final answer as
<h3>219.51 mL</h3>
Hope this helps you
Answer:
<h2>Actin and myosin.</h2>
Explanation:
The cells that allow your bones to move, the movement of thick (myosin) and thin (actin) filaments during contraction
.
During a contraction thick and thin filaments do not shorten but increase their overlap of each other.
Thin filaments slide past thick filaments extending more deeply into the A band.
The I bands and H bands decrease in lenght as Z discs are come closer together
.
Sarcomere represents area between two Z disc, so the sarcomere gets smaller during a contraction
.