Mix of Flow & Matter 3-4 Flashcards
What is viscosity?
how quickly fluids can flow
how is viscosity determined?
by a fluids internal friction
what’s the difference between fluids with high and low viscosity?
Fluids with high viscosity do not flow easily
Fluids with low viscosity flow easily
what is the effect temperature has on viscosity?
Heated fluids become less viscous (thinner)
Cooled fluids become more viscous (thicker)
what is the ramp method/how does it work?
Viscosity can be easily measured using the ramp method. Pour different liquids down a ramp and time how long it takes for each of them to get to the bottom.
The one that is the slowest will be the most viscous.
how does the particle model help us understand viscosity?
When a fluid is heated particles are able to move more easily past each other, flow rate increases
When cooled the particles slow their movement, friction increases, flow rate slows.
what is density?
Density is the amount of matter in a given volume.
Every substance has a different density, because each substance is made up of different particles.
The density of a substance depends on the particles it is made up of.
how do we get the mass density of an object?
The mass density of an object is simply its mass divided by its volume.
Density is the mass of a substance divided by its volume
This is shown in the following equation form:
Density (d) = mass (m)
-----------------
volume (V)
what determines density?
Density depends on:
- whether the object is solid
- filled with air pockets
- or something in between.
Density changes as temperature changes
what happens when liquids with different densities mix?
Substances that have a higher density than the density of the substance it is placed in will sink
Substances that have a lower density than the density of the substance it is placed in will float.
what are the units for density?
Solids
grams/cubic centimeters ( cm3)
g/cm3
Liquids
grams/milliliters ( mL )
g/mL
how do we determine the volume of an irregularly shaped object?
To determine the volume of an irregularly shaped object is to submerge the object in a full container of water.
The volume of the object equals the volume of water that overflows.
Ships can float because they contain large volume of air. The overall density of the ship is less dense than water, so it floats.
what’s a key difference between density and viscosity?
density does not change with temperature, viscosity does?
what is the particle model of matter’s connection with density?
The particle model of matter states that for every substance, the number of particles in a given volume, remain constant, if the temperature is kept constant.
As energy is added, the particles move more quickly and further apart, thus increasing the substance’s volume.
When this happens, the density of the substance (which is the mass to volume ratio) decreases because the mass remains constant, but the volume increases.
One substance can have different densities, depending on the state it is in.
Using the particle model of matter, as particles become more active, they move away from each other, and the space between them increases
This causes the volume to increase, (like when a liquid turns to a gas) but the number of particles stays the same…we are not adding or subtracting particles
The mass of the particles will stay the same, but now the volume is greater, so the formula for density will have different values, causing a variance in densities for the same material
explain the different temperature to different density pipeline
Yup. A substance will be most dense in a cooled, solid state. As the temperature increases, space is increased between the particles, and therefore the density of the substance decreases. (exception is water)
how can densities change with concentration?
Objects that are less dense than 1g/ml float in water.
The Dead Sea is one of the saltiest bodies of water on the Earth. When salt is added to water, there are more particles in a given volume, which increases the density of the water, allowing denser objects to float in the saltwater.
what is buoyancy?
Buoyancy is the tendency of a substance to float.
When an object is in a liquid, the force of gravity pulls it down. The liquid itself has a force that acts against the force of gravity. This buoyant force pushes objects upward.
The forces are measured in Newtons (N)
what is the difference between positive, neutral, and negative buoyancy?
Objects that are denser than water will sink (negative buoyancy)
Objects that are less dense than water will float (positive buoyancy)
Objects with the same density as water will hover (or, be suspended - (neutral buoyancy), neither sinking nor floating.)
what is the Plimsoll line?
Ships are designed to float in all types of water, regardless of the density of the water.
This is possible because of the Plimsoll Line- which shows how heavily a ship can be loaded in different water conditions.
how do hot air balloons use buoyancy?
Hot Air Balloons
As the air inside the balloon is heated, it becomes less dense than the surrounding air.
The buoyant force of the air will push the hot air balloon upwards, until the buoyant force equals the force of gravity.
what is compressibility?
When a force pushes on an object, the object is said to be under compression. Objects under compression tend to deform in shape. For example, when you kick a soccer ball, your foot causes a temporary deformation in the shape of the ball because you are compressing the air particles inside the ball which keep it inflated.
what are the differences in compressibility between liquids and gases?
The difference in the amount of space between particles indicates how compressible the substance will be.
As we know from the particle model, there is much more space between gas particles than that of solids, and even liquids.
Generally, solids and liquids are said to be incompressible…they cannot be compressed easily.
how do you calculate pressure?
Pressure is a measure of the amount of force applied to a given area.
p = F / A
p is pressure F is Force and A is Area
what is a pascal?
The unit of measurement for pressure is a pascal (Pa), named after Blaise Pascal who did important research on fluids.
1 Pascal is equal to the force of 1 Newton over an area of 1 m2
Force: Measured in Newtons
Area: measured in metres squared
how does depth correlate to pressure?
Water at the top of the container will press down on the water in the lower part of the container.
The more water above a hole, the greater the pressure, and the farther out the water will flow
The greater the depth of the water, the greater the pressure at that point.
what is Pascal’s law?
Pressure applied to an enclosed fluid is transmitted equally in all directions throughout the fluid.
how do pistons create pressure? how do pistons work?
In hydraulic systems, the pressure is created using a piston.
Pistons can be different sizes and hydraulic devices use pistons that are different sizes attached to each other with a flexible pipe.
The Input piston appies force to the fluid
The fluid transfers this pressure to the output piston.
This pressure exerts a force on the
output piston
Results in a mechanical advantage that makes the
hydraulic system very useful.
how do hydraulic pumps work?
A hydraulic lift is used to move a car above the ground, so a mechanic can work underneath it.
Small piston is the input piston
The large piston is the output piston
We apply a force to the input piston, it is transmitted throughout the liquid and pushes on the large piston
how do you problem solve with hydraulic and pneumatic devices?
If there is a problem with a hydraulic or pneumatic device, people will usually first check for a leak in the system.
If the tiniest hole exists, the fluid is able to escape, and the pressure will not be evenly distributed.
The system has to be completely closed, meaning no outside material is able to get in, and no inside material is able to get out.
what is a detergent?
something that can remove hydrophobic things, like dirt, from clothes
what is a surfactant?
Soap (the surfactant) encapsulates the fat & dirt molecules in the water, removing them from the fabric.
In this way the dirt and water forms an emulsion, which can then be drained away.
how does dry cleaning work?
Dry cleaning involves a chemical that attaches itself to the dirt and then is removed.
The chemical, (Perc) is then reused over and over again.
why are phosphates no longer used in detergents?
Phosphates were once used in detergents, but had adverse environmental side effects
Phosphates encourage plant growth, the phosphates would cause weeds to overgrow in water systems and choke out the sunlight.
how does scuba diving work?
S.C.U.B.A. gear (Self-Contained Underwater Breathing Apparatus)
Air tanks and regulators) allow humans to stay under water for extended periods
When going deeper, nitrogen can dissolve in the divers body cells and tissues in a higher concentration than normal.
As the diver rises slowly back to the surface, the nitrogen will leave the body gradually.
what is “the bends”? how can it be treated?
If the diver ascends too quickly the nitrogen gas bubbles out of the blood and tissue, or collects in different parts of the body causing extreme pain.
“The bends” can be treated in a hyperbaric chamber, which forces the nitrogen to re-dissolve back into the blood and tissue.
how do pumps work/what do they do?
To obtain water from below the surface (the groundwater) and to move a fluid through a fluid system, you need to use something that will work against the pull of gravity, a pump.
what do valves do?
Valves are devices that regulate the flow of a fluid.
Today’s valves can control flow, rate, volume, pressure or the direction of fluids, slurries or dry materials through a pipeline, chute or similar passageway.
turn on and turn off, regulate, modulate or isolate.
control flow of all types, from the thinnest gas to highly corrosive chemicals, superheated steam, abrasive slurries, toxic gases and radio active materials.
handle temperatures from cryogenic to molten metal, and pressures from high vacuum to thousands of pounds per square inch.
range in size from a fraction of an inch to as large as 30 feet in diameter
vary in complexity from a simple brass valve available at the local hardware store to a precision-designed, highly sophisticated coolant system control valve, made of an exotic metal alloy, in a nuclear reactor.
what are submersibles?
A deep-diving submarine used to explore the ocean is called a submersible.
Submersibles are usually smaller than submarines.
They are often equipped with external cameras, manipulating arms, and special lights.
Submersibles are built to do specific jobs, not for long-distance travel.
We use them to help us recover “black box” flight recorders from wrecked airplanes, bury cables in the sea floor, investigate ancient shipwrecks, map the ocean floor, look for signs of undersea earthquakes, study marine life, repair damaged offshore oil wells, take rock samples of the ocean floor, and study ocean currents.
what are in submarines/how do they work?
Inside a submarine there are containers called ballast tanks.
If these are full of air, the submarine will float.
Even though it is made of steel, the average density of the submarine is less than that of water.
By pumping water into the ballast tanks, the submarine can sink. This is because when its ballast tanks fill with water, the submarine has a greater density than water.
Submarines are designed for use at great depths.
The have rigid, double-walled hulls allow the crew to live and work normally underwater for as long as air and power supplies last.
Submarines are steered by turning a rudder left and right. A propeller moves the sub through the water–pushing against the water and creating a forward force.
how are submarines, buoyancy, and ballasts correlated?
Buoyancy is the upward force of water pushing against the submarine.
When an object is underwater, it pushes aside (or “displaces”) an amount of water equal to its volume.
An object floats if it displaces enough water to support its weight. Subs don’t sink because their metal shell (or “hull”) surrounds a volume weighing less than an equal amount of water.
Subs can sink, rise, and float underwater (maintain “neutral buoyancy”).
Subs do all this by adjusting the amount of water and air in their ballast tanks.
how do ballast tanks work?
When the tanks are full of air, the sub weighs less than the volume of water it displaces and it floats. When the ballast tanks are flooded with water, the sub weighs more than the water it displaces, and it sinks.
To rise again, the sub reduces its weight by pushing compressed air into the ballast tanks. The air forces the sea water out, and the sub goes up toward the surface.
To move beneath the surface and to hover, the amount of water in a submarine’s ballast tanks is made equal to the weight of the water it is displacing.
