topic 5 - solids, liquids and gases

Question 1

how to calculate density

Answer 1

density = mass/volume

ρ = m/V

Question 2

practical: investigate density using direct measurements of mass and volume

Answer 2

• the density of an object can be found by measuring the mass and volume and applying the formula above to calculate the density.
• for a regular object use a ruler to measure the lengths needed to determine the volume.
• for an irregular object submerge it in water and measure the displaced volume.
• measure the mass of either type of object using a measuring balance.

Question 3

how to calculate pressure

Answer 3

pressure = force/area

P = F/A

Question 4

what is pressure is gases and still liquids like

Answer 4

Pressure in gases and liquids acts equally in all directions as long as the liquid is not moving.

Question 5

how to calculate pressure difference

Answer 5

pressure difference = height x density x gravitational field strength

P = h x ρ x g

Question 7

3 gas laws

Answer 7

• Gas molecules have rapid and random motion.
• When they hit the walls of the container, they exert a force.
• Pressure = Force/Area

Question 8

what is absolute zero

Answer 8

0 Kelvins
-273 Celcius
particles have no thermal or kinetic energy, therefore do not exert a force

Question 9

Kelvin to Celcius conversion

Answer 9

0 Kelvin = -273 Celcius

Question 10

what happens to gas molecules when temperature increases

Answer 10

the kinetic energy of the gas particles increases and thus their average speed also increases.

Question 11

what is Kelvin temperature proportional to

Answer 11

kinetic energy of molecules

Question 12

Explain, for a fixed amount of gas, the qualitative relationship between: pressure and volume at constant temperature, pressure and Kelvin temperature at constant volume.

Answer 12

• As you heat the gas, the kinetic energy of the particles increases, and thus so does their average speed.
• This means more collisions per second with the walls, and they exert a larger force on the wall.
• This causes in the total pressure being exerted by the particles to rise.
• If temperature is constant, the average speed of the particles is constant.
• If the same number of particles is placed in a container of smaller volume they will hit the walls of the container more often.
• More collisions per second means that the particles are exerting a larger force on the wall over the same time, so average force exerted on the walls has increased.

Question 13

relationship between pressure and temperature

Answer 13

P1/T1 = P2/T2

Question 14

relationship between pressure and volume

Answer 14

P1V1 = P2V2