Solids Liquids And Gases

Question 1

What equation links density, mass and volume?

Answer 1

Density = mass / volume

Question 2

What are the units for density = mass / volume?

Answer 2

Kg, m³, kg/m³ or the reciprocal

G, cm³, g/cm³ or the reciprocal

Question 3

How do you convert from kg/m³, to g/cm³?

Answer 3

Divide by 1000

Question 4

How do you convert from g/cm³ to kg/m³?

Answer 4

Times by 1000

Question 5

How do you work out the volume of an irregular object?

Answer 5

Use a eureka can, fill the can with water until it pours out of the spout . Then place the object in the water and the amount of water displaced is the volume of the object (can then be used to work out density)
Or work out volume of water displaced by an object in a measuring cylinder

Question 6

What equation links pressure, force and area?

Answer 6

Pressure = force / area

Question 7

What are the units for pressure = force / area?

Answer 7

N, m², N/m²
N, cm², N/cm²
Or 1 N/m² = 1 Pascal (Pa)

Question 8

What happens to the pressure as water gets deeper and why?

Answer 8

The deeper you go, the greater the pressure, this is because pressure is due to the force applied by the liquid, and the deeper you got then the greater amount of liquid is above you, which exerts pressure.

Question 9

How does pressure in a liquid act on an object that is underwater (for example) ?

Answer 9

The liquid pushes on all surfaces in contact with the water, but because pressure increases with depth, the pressure at the bottom of the block is greater than the pressure on the top. This causes upthrust

Question 10

How does the pressure exerted by denser liquid compare to pressure exerted by less dense liquid?

Answer 10

Denser liquids exert a greater pressure and have a greater upthrust. This means that things float higher in denser liquids. Eg, a block floats higher in salt water than in normal water.

Question 11

What causes an object to float?

Answer 11

An object floats when the upthrust caused by the pressure of the liquid on an object balances the downward weight of an object.

Question 12

How do you calculate the pressure in a liquid?

Answer 12

Pressure = density of the liquid x g x h

Question 13

What are the units for P = ρ x g x h?

Answer 13

N/m² = kg/m³ x N/kg x m

Question 14

How do hydraulics work?

Answer 14

They use pressure exerted on liquids in closed systems, because forces can only be transmitted through a fluid if it is enclosed.

Question 15

Why do hydraulics work?

Answer 15

• In a liquid the pressure at any one level is the same
• Liquids are practically incompressible and the pressure in a liquid is transmitted equally in all directions.
• If a force is exerted on the end of an enclosed fluid, the pressure through the fluid is the same.

Question 16

What is a hydraulic jack an example of?

Answer 16

A force multiplier. Applying a small force to the jack can result in a large force being exerted on an object, because a small force acting on a small area is equal to a large force acting on a large area.

Question 17

What is atmospheric pressure?

Answer 17

It is the pressure due to the force exerted by the constant collisions of air molecules with the surface.

Question 18

Why is atmospheric pressure greater near the surface of the earth?

Answer 18

The density of air molecules is greater due to gravitational effects. This means that the atmospheric pressure is greater because there are more collisions per second. However as altitude increases, the density of air decreases so the atmospheric pressure decreases.

Question 19

What is a way to measure atmospheric pressure?

Answer 19

Using a Mercury barometer; a long glass tube full of mercury inverted over a pool of mercury

Question 20

How does a Mercury barometer work?

Answer 20

At sea level there are more air molecules which push down on the surface of the Mercury which helps support a larger weight of mercury in the tube (the Mercury rises higher). However, on Everest (for example), there are less air molecules pushing down on the Mercury so they are only able to support a small weight of mercury.

Question 21

What is the symbol for density?

Answer 21

Rho - ρ