(a) Which have more kinetic energy – the particles in a
drop of hot chocolate or those in a bathtub full of cold
water?
(b) If the bathtub were full of that same hot chocolate,
which particles would have more thermal energy?
What is zero degrees Kelvin? What is its significance?
Zero degrees Kelvin is absolute zero, the theoretical
temperature at which particles cease moving.
(a) The hotter particles have more kinetic energy.
(b) The bathtub, at the same temperature, would
have more thermal energy than just a drop.
Where is the melting point on a heating curve?
Where is the gas state on a phase diagram?
The melting, or freezing point, is the first horizontal line,
which reflects the point at which the solid becomes a
liquid. It is not just a point on a heating curve, but is a
line, reflecting that it takes some time for all particles to
change state.
At equal pressure (y-axis), the gas state will be located
at the far right, reflecting that it is the state at the
highest temperatures (x-axis).
What is the triple point?
The triple point is the point on a phase diagram where
all three states of matter (solid, liquid, gas) can exist
simultaneously. The point is at a certain pressure (yaxis) and temperature (x-axis).
(a) What is the formula for Boyle’s law?
(b) If a balloon starts with a volume of 5.0 L at
100 kPa, what will be its volume when the
pressure doubles?
(a) P1V1 = P2V2.
(b) The final pressure will be 2.5 kPa.
(a) Which displaced more water in our in-class lab:
the clay ball or the canoe?
(b) Whose principle did this lab demonstrate?
What is the purpose of a hydraulic system?
(a) The canoe displaced more water; the weight
force of that displaced water is equal to the
buoyant force. Because the canoe floated, we
know there was a greater buoyant force acting
upon it than on the ball.
(b) This is Archimedes’ principle.
Its purpose is to transfer a small force over a small
area to a large force over a larger area, thereby
enabling us to lift heavy objects without much effort.
(a) What is the general formula demonstrating
Pascal’s principle?
(b) How do you apply it to hydraulic devices?
(a) General formula: P=F/A
(b) When you have a hydraulic device with two
forces and areas: F1/A1 = F2 /A2
What is viscosity? Compare the viscosity of milk and
the viscosity of molasses.
Viscosity is a liquid’s resistance to flow, based on how
much the liquid’s particles are attracted to each other.
The stronger the attraction between the liquid’s particles,
the more viscous. Molasses is much more viscous than
milk.
What is Bernoulli’s principle? Give an example from
our station lab that demonstrates it and explain how.
As the speed of a fluid increases, the pressure decreases.
One example: remember the floating ping pong ball –
the rush of air in the middle was slightly faster than the
air on the edges and the pressure there is therefore the
lowest, so the ball seeks to stay centered there.
An object has a mass of 200 g. You place it in a tank
of water and 300 mL are displaced. Does the object
sink or float?
If 300 mL of water are displaced, then that is equal to
300 g of water (you know its density is 1 g/mL). The
weight of the displaced water is therefore more than
the weight of the object, so the object floats because
the buoyant force is greater than the weight force.
Two boats in a flowing river are sailing side-by-side
with only a narrow space between them. What
happens to the fluid speed and the pressure between
the two boats? How could this cause a crash?
Fluid speed increases and fluid pressure decreases. If
the pressure on the outside of the boats is greater than
the pressure between them, the boats are pushed
together (to fill the void, like the balloons coming
together and the index card caving in!)
If Elmo pushes down on a piston with an area of 1
square centimeter with 10 N of force, will he be able
to lift Snuffleupagus, who weighs 22,000 N and is
standing on a piston of 2000 square centimeters?
Sorry, Elmo. The other piston would have to be 2200
square centimeters, or Snuffleupagus would have to
lose weight to get under 20,000N.
F1/A1 = F2 /A2