P3 Particle Model of Matter

Question 1

how can you view the particles that make up matter in particle theory?

Answer 1

as tiny balls

Question 2

what is different in the particles of a substance in each state?

Answer 2

the arrangement and energy of the particles

Question 3

describe solids

Answer 3

strong forces of attraction hold the particles close together in a fixed, regular arrangement. The particles don’t have much energy so they can only vibrate around their fixed positions

Question 4

describe liquids

Answer 4

there are weaker forces of attraction between the particles. The particles are close together, but can move past each other, and form irregular arrangements. They have more energy than the particles in a solid - they move in random directions at low speeds.

Question 5

describe gases

Answer 5

There are almost no forces of attraction between the particles. The particles have more energy than in liquids and solids - they’re free to move, and are constantly moving with random directions and speeds

Question 6

what creates pressure?

Answer 6

colliding gas particles

Question 7

what is pressure?

Answer 7

when particles in a gas collide with something (like the walls of a container) they exert a force on it. Pressure is the force exerted per unit area.

Question 8

how can increasing the temperature of a gas increase pressure?

Answer 8

when you heat up a gas you transfer energy to the kinetic energy stores of its particles. The temperature of a gas is related to the average energy in the kinetic energy stores of the particles in the gas. The higher the temperature, the higher the average energy. So as you increase the temperature of a gas, the average speed of its particles increases. This is because the energy in the particles’ kinetic energy stores is 0.5mv^2. This means that, for a gas at a constant volume, increasing its temperature increases its pressure as the particles are travelling quicker, so it means they hit the sides of the container more often in a given amount of time. Each particle also has a larger momentum with means that they exert a larger force when they collide with the container.

Question 9

what are the units of density?

Answer 9

kg/m^3 or g/cm^3

Question 10

how many kg/m^3 are there in 1 g/cm^3?

Answer 10

1g/cm^3 = 1000kg/m^3

Question 11

what is the equation for density?

Answer 11

density = mass / volume

Question 12

what is the symbol for density?

Answer 12

the greek letter rho, which looks like a p

Question 13

put the states of matter in order of increasing density

Answer 13

gas, liquid, solid

Question 14

how do you find the density of a regular solid?

Answer 14

use a balance to find the mass of the object, and then measure its length, width and height with a ruler. calculate the volume with the relevant formula for that shape, and then use the equation density = mass / volume to find the density

Question 15

how do you find the density of an irregular solid?

Answer 15

use a balance to measure the mass of the object, then find the volume by submerging it in a displacement can filled with water. The water displaced by the object will be transferred to the measuring cylinder. Record the volume of the water in the measuring cylinder - this is the volume of the object. Then use the formula density = mass / volume to find the density

Question 16

how do you find the density of a liquid?

Answer 16

Place a measuring cylinder on a balance and zero the balance. Pour 10ml of the liquid into the measuring cylinder and record the liquid’s mass. Pour another 10ml into the measuring cylinder, repeating the process until the cylinder is full, recording the total volume and mass each time. For each measurement use the formula density = mass / volume to find the density (1ml = 1cm^3), and then take an average of your calculated densities. This will give you a value for the density of the liquid

Question 17

what is it called to go directly from a solid to a gas?

Answer 17

sublimination

Question 18

is a change of state a chemical or physical change? What does this mean?

Answer 18

physical - this means you don’t end up with a new substance - it’s’ the same substance you started with, just in a different form. If you reverse a change of state (e.g. freeze a substance that has been melted), the substance will return to its original form and get back its original properties

Question 19

is mass conserved in a change of state?

Answer 19

yes

Question 20

in a sealed container, what is the outward gas pressure?

Answer 20

the total force exerted by all of the particles in the gas on a unit area of the container walls

Question 21

give two things the particle model can be used to explain

Answer 21

1. the different states of matter

2. differences in density

Question 22

what does the density of an object depend on?

Answer 22

what it’s made of and how its particles are arranged