Phase Change

Why does a phase change graph have flat lines?

A phase change graph demonstrates how the temperature is affected by how much energy is added to a substance. For example, in order for an ice cube to melt it has to absorb energy from it's surroundings. As the ice melts it's temperature will, in fact, stay the same (this was seen in an experiment done in class). The flat lines on a phase change graph show that during that period of time there was no change in temperature. The water is absorbing energy which is being converted into potential energy. This potential energy is used to change the water from one state of matter into another (solid - liquid - gas ). The graph shows that there are two types of energy being absorbed: kinetic and potential. The kinetic energy creates a change in temperature and is demonstrated in the sloping lines. When potential energy is absorbed is creates a change in the state of matter. The temperature will stay the same, hence the flat lines. The water will never absorb both kinetic and potential energy at the same time. Observe the graph above.

Calculate Q1, Q2, Q3

M x C x DT = Q

Q1:
394.5g x 4.184J/goC x 0 = 0 J

Q2:
394.5 x 4.184J/goC x 50 = 82529.4

Q3:
 394.5g x 4.184J/goC x 97 = 160107.036 J

Archer Fish: Snell's Law

The archer fish makes several instinctive calculations in order to catch its prey. These calculations are all to do with refraction from the air to the water. The archer fish must recognize the angle in which it will begin to shoot the water. Then it must calculation the angle of refraction in the air. The target is actually further away than it seems. The fish will have to direct its jet of water further away than the insect seems to be. It must calculate the angle of refraction. This is the angle that the fish must direct its jet of water (instead of straight up towards the target).

The calculations the fish must make are called "Snell's Law".
They look like this:
n1/n2 = Sinθ2/Sinθ1
n = refraction index
Sinθ= The angle of light

The fish instinctively uses this formula to calculate the angle of light in the air. This way it can locate the target's exact location.