States of matter and the particle model

Question 1

What are the three states of matter?

Answer 1

-solid, liquid and gas

Question 2

The properties of a substance are…

Answer 2

… really just the properties of a huge number of particles together.

Question 3

Properties of a solid

Answer 3

-fixed shape and cannot flow, as the particles cannot move from place to place (just vibrate)
-cannot be compressed as particles are close together and have no space to move into

Question 4

Properties of a liquid

Answer 4

-flow and take the shape of their container, as particles can move around each other
-cannot be compressed as particles are close together and have no space to move into

Question 5

Properties of a gas

Answer 5

-flow and completely fill their container, as particles move quickly in all directions (spread)
-can be compressed as particles are far apart and have space to move into

Question 6

Atom

Answer 6

-smallest part of an element that can exist by itself

Question 7

Molecules

Answer 7

-collection of two or more atoms held together by chemical bonds

Question 8

Ions

Answer 8

-electrically charged particle, formed when an atom/ molecule gains/loses electrons

Question 9

What determines whether the particles in a substance are atoms, molecules or ions?

Answer 9

-depends on the type of substance
e.g. ionic compounds, small molecules, giant molecules, and metals

Question 10

What is it called when substances can change directly from solid to gas or gas to solid without being a liquid in between?

Answer 10

-sublimation

Question 11

What must happen for a substance to melt, evaporate or boil?

Answer 11

-energy must be transferred by heating
-particles gain energy which is used to
> break some of the bonds between particles during melting
> overcome the remaining forces of attraction between particles during evaporating or boiling

Question 12

Melting

Answer 12

-process where a solid turns into a liquid when it is heated

Question 13

Evaporating

Answer 13

-process where a liquid changes state and turns into a gas

Question 14

Boiling

Answer 14

-changing from liquid to gas, where bubbles form throughout the liquid

Question 15

Evaporation vs Boiling

Answer 15

Evaporation:
-occurs only at the surface of a liquid
-particles gain enough energy to escape into the gas phase without the liquid reaching its boiling point
-no bubbles form—just gradual escape of particles
Boiling:
-occurs throughout the liquid
-occurs when the liquid reaches its boiling point, gains enough thermal energy for all particles to turn into gas
-bubbles of gas form inside the liquid, rise to the surface, and escape

Question 16

Why does evaporation occur at the surface?

Answer 16

-particles gain enough energy to break free and escape
-only particles exposed to surrounding air, so nothing on top of them holding them in

Question 17

What does the amount of energy required to change from solid- liquid- gas depend on?

Answer 17

-the strength of the forces between the particles of a substance
-the stronger the forces of attraction, more energy is required

Question 18

If a substance has a high melting and boiling point it means…

Answer 18

…that there a strong forces between its particles.

Question 19

What happens, in terms of energy, when something condenses or freezes?

Answer 19

-energy is transferred form a substance to its surroundings
-so we get rid of the energy that broke apart those strong forces of attraction between the particles

Question 20

The melting point of oxygen is -218°C and its boiling point is -183°C. Predict the state of oxygen at -200°C

Answer 20

-liquid state at -200°C (because this is between its melting and boiling points)

Question 21

Limitations of particle model

Answer 21

-assumes particles are solid spheres
-particles are not solid, as atoms are mostly empty space
-many particles are not spherical