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20 Cards in this Set
- Front
- Back
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For an incompressible fluid (liquid) how does pressure relate to depth? |
Pressure is directly proportional to the depth. |
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In gases, how are density and pressure related? |
As density increases, pressure increases. |
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Why does bromine spread more slowly in air than in a vacuum? |
The bromine atoms collide with the atoms and molecules making up the air, hindering their movement. |
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Describe the effect of Brownian motion on smoke particles. |
Smoke particles are bombarded by atoms and molecules in the air, which have momentum and exert a force on the smoke particles. The collisions are random and the particles are small. At any time, a resultant force exists as there are more collisions taking place on one side of the particle than the other. The direction of the resultant force continually changes, producing the jerky, random movement. |
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What is the kinetic theory of gases? |
A statistical treatment of the movement of gas molecules, in which macroscopic properties such as air pressure can be interpreted by considering molecular movement. |
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What are the assumptions of kinetic theory? |
Negligible Gravitational effects on the molecules. Between the molecules there are no Intermolecular forces, except during collisions. Molecules have negligible Volume compared to the whole gas. Molecules undergo perfectly Elastic collisions with the container walls. There are an Equal number of molecules moving in each direction. Statistical rules can be used with certainty because of a Large number of molecules. Each molecule produces Force on the container wall. Molecules are in constant rapid Motion Huge no. of molecules averages to give a Uniform pressure throughout the gas. Negligible Duration of collision compared to time between collisions. |
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Why is there 1/3 in the eqn . pV=1/3Nm<c^2> ? |
On average 1/3 of the molecules are moving in each of the x, y and z directions of 3D space. |
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What happens if the number of molecules of gas in a container is increased? |
Collisions happen more frequently everywhere, so the pressure increases. Twice as many molecules doubles the rate of collision with the walls, so doubles the pressure. |
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What else is the molecular speed of a gas related to? |
The gas's Temperature. |
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What affect do internal collisions between the particles have on the rate of collision with the walls and the pressure? |
None, as the collisions are all elastic so momentum is conserved, and is therefore just reversed. |
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How can the equation pV=1/3Nm<c²> be rearranged to give another useful form (not on the formula sheet? ^2> |
p=1/3(Nm/V)<c²> Nm is the mass of the gas, so: p=1/3ρ<c²> |
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What is Boyle's law? |
IfT is constant, Pα1/V |
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What is Charles' law? |
If P is constant VαT |
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What is the pressure law? |
If V is constant PαT |
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What do Boyles', Charles' and the Pressure law combine to give? |
P1V1/T1=P2V2/T2 |
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What happens when a bicycle pump is used to inflate a tyre inner tube? |
The pump adds extra air molecules to the tube, which increases the pressure. The volume remains almost constant (although it will expand a little against surrounding air pressure). The pump rises in temperature due to U=Q+W. |
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What is Avogadro's constant? |
The number of atoms in 1 mole. |
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What is Avogadro's law? |
Equal volumes of all gases at the same temperature contain the same number of molecules. |
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How does the mass number of an element relate to Avogadro's constant? |
That mass of the element in grams contains Avogadro's number of molecules. |
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How does the temperature of a gas relate to its energy? |
The mean translational KE (due to motion in line not rotation) of the gas molecules is directly proportional to the absolute temperature. |
