8 — Kinetic particle model of matter

Question 1

State the arrangement of particles, movement, ability to be compressed, density and forces of attraction in a solid.

Answer 1

• closely packed tgt in an orderly manner
• vibrate abt their fixed positions
• v closely packed tgt in an orderly manner -> v little space betw particles to move closer tgt -> force exerted -> Unable to be compressed
• held tgt by v strong forces of attraction

Question 2

State the arrangement of particles, movement, ability to be compressed, density and forces of attraction in a liquid.

Answer 2

• closely packed tgt in a disorderly manner
• slides over one another throughout the liquid due to more space present betw particles than solid -> def vol but no def shape
• closely packed tgt but further apart than in solid in a disorderly manner -> little space betw particles to move closer tgt -> force is exerted -> distance cannot be reduced further -> Unable to be compressed
• held tgt by strong forces of attraction

Question 3

State the arrangement of particles, movement, ability to be compressed, density and forces of attraction in a gas.

Answer 3

-far apart and arranged in a disorderly manner
-move randomly in all directions in high spds -> no def vol + def shape
-far apart and arranged in a disorderly manner -> there is space betw particles to move closer tgt -> force exerted -> can be compressed
- held tgt by v weak forces of attraction

Question 4

Explain why solids and liquids hv relatively high densities

Answer 4

Solids: Molecules v closely packed tgt -> large no. Of particles per unit volume -> higher density.
Liquids: molecules closely packed tgt -> large no. Of particles per unit volume -> high density

Question 5

Explain in terms of internal energy, why is the tempt constant when obj changes state.

Answer 5

Obj undergoes change of state from _ to _ without change in tempt. Thermal energy is transferred to obj during [process], increasing only energy in internal potential store to overcome all/some attractive forces betw particles as average separation of particles increases. Since average ke remains constant, tempt of obj remains constant.

Question 6

Explain how gas supports a weight using KTM.

Answer 6

Gas contains many particles moving constantly n randomly in high spds in all direction, colliding w the walls of obj, exerting an average force on obj to support the weight. Total force exerted by gas per unit area creates a pressure acting on obj.

Question 7

Compression obj in SLG

Answer 7

Arrangement of particles + distance betw molecules: small/big -> distance can/cannot be reduced when force is exerted -> compressible/non-compressible

Question 8

Expansion of particles in KTM

Answer 8

Obj heated -> ave energy in ks ^ -> ave spd of particles ^ -> particles vibrate/ slide past one another faster ->
(if more marks: more energetic particles in obj transfer energy to less energetic particles in obj thru collisions -> internal energy increases ->)
particles move further apart -> matter expands
(If SLG: liquids expand more easily than solid -> more noticeable change)

Question 9

Why heating increases pressure

Answer 9

thermal energy increases, increasing energy in ave. Ke store of particles-> particles move faster, increasing vigorous and frequency of collision of particles with INNER walls of glass box and BETWEEN PARTICLES. Increased average force acting on INNER walls per unit area increase pressure by P = F/A

Question 10

Reasons y particles collide

Answer 10

By kinetic model of matter, air molecules r alw in constant random motion
Particles undergo Brownian motion as air molecules collide unevenly onto them w diff spds.

Question 11

Define Brownian motion

Answer 11

Refers to the random motion of particles that r suspended in a fluid

Question 12

Define temperature

Answer 12

Measure of the average (collection of particles, not single particle) kinetic energy of the particle of a substance

Question 13

Suggest why the hydraulic press does not work properly if the oil contains bubbles of air

Answer 13

Since air is compressible, pressure of air in oil must hv additional work done to compress the volume change of the bubble

Question 14

Suggest y Brownian motion is not observed w very large particles

Answer 14

V large particles hv larger masses -> larger weight acting on particles than resultant force exerted by collision from fluid particles -> fall towards earth due to its weight.

Question 15

What happens to the thermometer when water is heated

Answer 15

Substance heated -> energy in kinetic store of particles increases -> particles vibrate/move faster -> more energetic particles in water transfer some energy to less energetic particles in thermometer in contact w water, thru collisions. -> more energy, particles tend to push each other further apart so the matter expands. Since liquids expands more easily than solids -> liquid column in thermometer expands noticeably along calibrated scale but length of thermometer’s glass body hardly changes.

Question 16

Why pressure increases when volume decreases

Answer 16

Decrease in vol -> distance betw molecules decreases -> more no. Of molecules per unit volume -> frequency of collision with walls of substance substance increases-> greater force exerted -> greater total force per unit area -> greater pressure

Question 17

Explain how small air molecules create great pressure

Answer 17

Large number of air molecules move at v high spds -> high frequency of collision w walls of substance -> large force applied by collision on a small contact area -> applying a high pressure

Question 18

Describe an experiment that proves Brownian motion

Answer 18

Smoke cell. Smoke particles move in constant and random motion.

Question 19

State 2 conclusions about movement of molecules shown by Brownian motion.

Answer 19

1. Molecules of fluids r in constant random motion. These molecules collide into larger smoke particles small and light enuf to be suspended by collision of fluid particles.
2. When molecules collide and bombard larger smoke particles, fluid molecules cause larger smoke particles to experience resultant force and large smoke particles move in direction of resultant force.

Question 20

State 2 reasons why collisions between air molecules and smoke particles cause the smoke particles to move randomly, [2]

Answer 20

1. The air molecules are moving in different directions and colliding with the smoke particles in a random and continuous manner.
2. The air molecules are moving at different speeds due to different temperature of the air molecules.

Question 21

Explain why the energy of a liquid decreases as it turns into a solid at the melting point. [1]

Answer 21

As the liquid changes to solid, the liquid molecules releases latent heat of fusion, resulting in liquid molecules moving closer together to become more closely packed with stronger intermolecular forces of attraction as average separation between molecules decreases hence potential energy decreases. Thus internal energy of the substance decreases.