Kinetic Theory And States Of Matter

Question 1

what are the three states of matter

Answer 1

• solid
• liquid
• gas

Question 2

what do all the particles in each (pure) substance have in common

Answer 2

they are all the same type of particle

Question 3

what is the difference between the particles in the three states of matter

Answer 3

the arrangement and energy of the the particles is different

Question 4

what happens on a particulate level when you reverse a change of state

Answer 4

the particles go back to how they were before

Question 5

what type of changes are changes of state and why

Answer 5

• physical changes

- because only the form of the substance changes

Question 6

what is the difference between changing of states and chemical reactions

Answer 6

• during changes of state, the energy levels and arrangement of particles are different with no chemical change in the substance itself
• whereas in chemical reactions, new substances are created by the reaction

Question 7

what are the particles like in a solid

Answer 7

strong forces of attraction hold the particles close together in a fixed and regular arrangement

Question 8

how do particles move in a solid

Answer 8

• the particles dont have much energy in their kinetic energy stores
• so they can only vibrate about their fixed positions

Question 9

what are the particles like in a liquid

Answer 9

• the forces of attraction between the particles are weaker than in solids
• the particles are close together, but can move past each other to form irregular arrangements

Question 10

how do particles move in a liquid

Answer 10

• they have more energy in their kinetic energy stores than in solids
• so they move in random directions at low speeds

Question 11

what are the particles like in a gas

Answer 11

there are almost no forces of attraction between the particles, meaning that there is no arrangement

Question 12

how do particles move in a gas

Answer 12

• particles have more energy in their kinetic energy stores than in liquids and are free to move
• they travel in random directions at high speeds

Question 13

what is the thermal energy store of a substance

Answer 13

the energy that is held in the kinetic energy stores of the particles that make it

Question 14

what happens when you heat a liquid

Answer 14

• the extra energy is transferred to the kinetic energy stores of the particles
• making them move faster

Question 15

when do liquids boil

Answer 15

• when enough of the particles have enough energy to overcome their attraction to each other
• and big bubbles of gas start to form in the liquid

Question 16

what happens when you heat a solid and what is the process called

Answer 16

• the extra energy makes the particles vibrate faster
• until the forces between them are partly overcome (weakened) and the particles start to move around
• this is melting

Question 17

in terms of volume, mass and density, which variables change when a substance changes shape

Answer 17

• the mass doesnt change
• the volume changes
• and therefore the density changes

Question 18

why doesnt the mass of a substance that has changed state change

Answer 18

• because mass is the measure of the amount of atoms or particles making a substance
• and when the substance has changed state, there are still the same number of particles and atoms making it as the particles arent changing
• so the mass always remains the same

Question 19

why does the density of a substance that has changed state from a solid to a liquid decrese

Answer 19

• particles in a solid are more tightly packed together than in a liquid
• when the substance changes shape to a liquid, the particles have more distance between them than they previously had (with weaker bonds and more kinetic energy)
• and as density is the measure of the number of particles in a given area (the compactness of an object), a lower number of particles in the same area in a liquid means it is less dense
• given that there are the same number of particles as before

Question 20

how does the volume change when a substance changes state from a solid to a liquid

Answer 20

• the volume increases
• due to the reason that the density decreases (less particles in the same ares)
• and as volume = mass / density, a constant mass but a lower density means that the volume would be higher