Chapter 20: Gases

What happens when a piston is pushed downward?

If the piston is pushed downward so that the volume is half the original volume, the density of molecules will be doubled, and pressure will be correspondingly doubled

Boyle's Law

Pressure x volume= different pressure x different volume for a given gas. The product of pressure and volume for a given mass of gas is a constant as long as the temperature does NOT change

If you squeeze a balloon to one-third its volume, by how much will the pressure inside increase?

The pressure in the balloon is increased three times. No wonder balloons break when you squeeze them!

A piston in an airtight pump is withdrawn so that the volume of the air chamber is increased five times. What is the change in the pressure?

The pressure in the piston chamber decreases to 1/5. This is the principle behind a mechanical vacuum pump

A scuba diver 10.3 m deep breathes compressed air. If she hold her breath while returning to the surface, by how much does the volume of her lungs tend to increase?

Atmospheric pressure can support a column of water 10.3m high, so the pressure in the water due to the weight of the water alone equals atmospheric pressure at depth of 10.3 m. Unfortunately for the scuba diver, her lungs will tend to inflate to twice the

Archimedes' Principle for Air

An object surrounded by air is buoyed up by a force equal to the weight of the air displaced

In what case will an object rise?

Any object that has a mass less than the mass of an equal volume of surrounding air will rise. In other words, any object less dense than the air will rise.

What are you looking at when you see a large dirigible airship (blimp) aloft in the air

When you see a blimp, think of a giant fish. Both remain aloft as they swim through their fluids for the same reason; they both displace their own weights of fluid. When in motion, the blimp may be raised or lowered by horizontal rudders or "elevators

Is there a buoyant force acting on you? If there is, why are you not buoyed up by this force?

There IS a buoyant force acting on you, and you ARE buoyed upward by it. You don't notice it only because your weight is so much greater

Two balloons are inflated to the same size, on with air and the other with helium. Which balloon experiences the greater buoyant force? Why does the air-filled balloon sink and the helium-filled balloon float?

Both balloons are buoyed upward with the same buoyant force because they displace the same weight of air. Ther eason the air-filled ballon sinks in the air is because it is heavier than the buoyant force that acts on it. The helum-filled balloon is lighte

Explain the reason water is always the same amount that flows in any section of a pipe

Consider a continuous flow of water through a pipe. Because water doesn't "bunch up", the amount of water that flows past any given section of the pipe is the same as the amount that flows past any other section of the same pipe. This is true whether the

Bernoulli's Principle

When the speed of a fluid increases, the pressure drops

What's the pressure like in fast moving water?

The pressure within fast-moving water in a fire hose is relatively low, whereas the pressure that the water can exert on anything in its path to slow it down may be huge.

Explain drinking through a straw

The operation of a barometer is similar to the process of drinking through a straw. By sucking, you reduce the air pressure in the straw that is placed by the drink. Atmospheric pressure on the liquid's surface pushes the liquid up into the reduced-pressu

How do the old-fashioned type of pumps work?

The old-fashioned farm-type pumps operate by producing a partial vacuum in a pipe that extends down into the water below. The atmospheric pressure exerted on the surface of the water simply pushes the water up into the region of reduced pressure inside th

What's a unique way you can crush a can?

YOu can crush a can by making it empty of air inside and putting a tight cap on it. There is so much atmospheric pressure on the outside and none on the inside that the can is crushed! There is no force to resist the forces of the atmosphere

Aneroid Barometer

An instrument used to measure atmospheric pressure, based on the movement of the lid of a metal box. The box has a lid that bends in or out as the atmospheric pressure changes. Motion of the lid is indicated on a scale by a mechanical spring-and-lever sys

Altimeter

An aneroid barometer calibrated for altitude

Describe the air pressure inside inflated tires of an automobile

The air pressure inside the inflated tires of an automobile is considerably more than the atmospheric pressure outside. The density of air inside is more than it is outside the tires. Inside the tire, molecules behave like tiny ping-pong balls, perpetuall

Suppose there are twice as many molecules in the same volume...

Suppose there twice as many molecules in the same volume- the density is then doubled. IF the molecules move at the same speed, or, equivilently, if they have the same temperature, then, to a close approximation, the number of collisions will double. This

What is common between liquids and gases. What is different?

Gases are similar to liquids in that they flow; hence, both are called fluids. The primary different between gases and liquids is the distance between molecules. In liquids, the molecules are close together, where they c ontinually experience forces from

Is it true that we live in an ocean of gas?

Yes, we live in an ocean of gas, our atmosphere. Molecules in the air ccupy space and extend many kilometers above Earth's surface. The molecules are energized by sunlight and kept in continual motion. Without Earth's gravity, the y would fly off into out

When does the density of the atmosphere decrease

The density of the atmosphere decreses with altitude. Air is more compressed at sea level than at higher altitudes. The air gets thinner and thinner (less dense_ the high a person goes; it eventually thins out into space

List two areas of the atmosphere

The troposphere, which is at the bottom part of the atmosphere and the stratosphere, which is the high portion of the atmosphere.

Does the atmosphere exert pressure?

The atmosphere, much like the water in a lake, exerts pressure. And just as water pressure is caused by the wight of the water, atomspheric pressure is caused by the wight of air

How much additional air does it take to pressurize your standark commerical jet, usually?

1,000 kg

Is the pressure of the atmosphere uniform?

The pressure of the atmosphere is NOT uniform. There are variations in atmosphere pressure at any locality due to the moving air currents and storms. Measurement of changing air pressure is important to meteorologists in predicting weather.

Why doesn't the pressure of the atmosphere break windows?

The atmospheric pressure doesn't normally break windows because it acts on BOTH sides of a window. So no net force is exterted by the atmosphere on the windows

*Barometer

instrument used for measuring the pressure of the atmosphere

When does the barometer "balance"?

The barometer "balances" when the weight of liquid in the tube exerts the same pressure as the atmosphere outside. If the atmospheric pressure increases, then the mercury will rise in the barometer. The mercury is literally pushed up into the tube of a ba

Streamlines

The smooth path of a small region of fluid in a steady flow

In a steady flow, one small bit of fluid follows...

In a steady flow, one small bit of fluid follows along the same path as a bit of fluid in front of it

Eddy

Changing, curling paths in turbulent flow of a fluid

What happens if the flow speed is too great?

If the flow speed is too great, the flow may become turbulent and follow a chnaging, curling path known as an eddy. In that case, Benoulli's principle does NOT hold true.

Bernouli's principle partly accounts for the flight of birds and aircrafts..

Bernoulli's principle partly accounts for the flight of birds and aircrafts. The shape and orientation of the wings ensure that air passes somewhater faster over the top surface of the wing than beneath the lower surface. Pressure above the wing is less t

lift

In application of Bernoulli's principle, the net upward force produced by the difference between upward and downward pressures when lift weight, horizontal flight is possible. The lift is greater for higher speeds and larger wind areas. Hense, low-speed g

fuselage

The fuselage (from the French fusel� "spindle-shaped") is an aircraft's main body section that holds crew and passengers or cargo.

When does atmospheric pressure decrease?

Atmospheric pressure decreases in strong wind. Air pressure above a roof is less than air pressure inside the bilding when wind is blowing. This preduces a lift that may result in the roof being blown off, AHAHAHA. Foos are usually constructed to withstan

What happens when a moving ball spins?

When a moving ball spins, unequal air pressures are produced on opposite sides of the ball.

Explain the bathroom shower curtain being swept inward

Air near the water stream flows into thelower pressure stream and is swept downward with the falling water. Air pressure outside pushed the curtain inward. The next time you're taking a shower and the curtain swing in against your legs, think of Daniel Be