Particle Model Of Matter

Question 1

The density of a material

Answer 1

The density of a material is defined by the equation
density =
mass/ Volume
ρ =m/V
* density, ρ, in kilograms per metre cubed, kg/m3
* mass, m, in kilograms, kg
* volume, V, in metres cubed, m3

Question 2

What can the particle models be used to explain

Answer 2

The particle model can be used to explain
* the different states of matter
* differences in density.

Question 3

How do changes of state differ from chemical changes?

Answer 3

Changes of state are physical changes which differ from
chemical changes because the material recovers its
original properties if the change is reversed.

Question 4

Required practical activity: use appropriate apparatus to make and record the measurements needed to determine the
densities of regular and irregular solid objects and liquids.

Answer 4

Aim:
To determine the density of regular and irregular solid objects and liquids.

Apparatus:
Balance (to measure mass)
Ruler (for measuring dimensions of regular objects)
Measuring cylinder or displacement can (to measure the volume of liquids and irregular solids)
String (if needed to suspend irregular objects)
Calculator (for density calculation)
Method:
For Regular Solid Objects (e.g., a cube or cylinder):
Measure the mass: Use a balance to measure the mass of the object (in grams).
Measure the volume:
For a cube or rectangular object, use a ruler to measure the length, width, and height, then calculate the volume using the formula:
Volume
=
length
×
width
×
height
Volume=length×width×height
For a cylinder, measure the radius and height, then use the formula:
Volume
=
𝜋
×
radius
2
×
height
Volume=π×radius
2
×height
Calculate the density:
Use the formula:
Density
=
Mass
Volume
Density=
Volume
Mass
​

For Irregular Solid Objects:
Measure the mass: Use the balance to measure the mass of the irregular object.
Measure the volume using water displacement:
Fill a measuring cylinder with water and record the initial volume.
Submerge the irregular object completely in the water and record the new volume.
The volume of the object is the difference in water levels (initial volume – final volume).
Calculate the density:
Use the same density formula:
Density
=
Mass
Volume
Density=
Volume
Mass
​

For Liquids:
Measure the mass of an empty container.
Add the liquid: Pour the liquid into the container and measure the new mass.
Calculate the volume: Use the measuring cylinder to measure the volume of the liquid directly.
Calculate the density:
Density
=
Massofliquid
Volumeofliquid
Density=
Volumeofliquid
Massofliquid
​

Safety Considerations:
Be careful when handling liquids to avoid spills.
If using heavy objects, handle them carefully to avoid injury.
Ensure equipment is stable during measurements.
Conclusion:
This experiment allows you to determine the density of various objects by measuring their mass and volume. Comparing the densities of different materials will help understand their properties and how density relates to state and composition.

Question 5

convert mass units into kg and volume unit into m3
.

Answer 5

If the mass is in grams (g), divide by 1000 to convert to kilograms:
Mass(kg)
=
Mass(g)
1000
Mass(kg)=
1000
Mass(g)
​

Example: If the mass is 250 g, then:
Mass(kg)
=
250
1000
=
0.25
 
kg
Mass(kg)=
1000
250
​
=0.25kg

Question 6

recognise/draw simple diagrams to model the difference
between solids, liquids and gases.

Answer 6

1. Solids:
   Arrangement: Particles are closely packed in a regular pattern.
   Movement: Particles vibrate in place but do not move past each other.
   Diagram:
   Draw particles (dots) in rows, tightly packed.
   Indicate slight vibration (wiggling arrows) within the particles.
   Example:

Copy
* * * * *
* * * * *
* * * * *
2. Liquids:
Arrangement: Particles are still close but not in a fixed pattern.
Movement: Particles move around each other and can slide past one another.
Diagram:
Draw particles in random positions but still fairly close.
Indicate movement with arrows showing the sliding motion.
Example:

Copy
* * * * *
* * * *
* * * *
3. Gases:
Arrangement: Particles are far apart and arranged randomly.
Movement: Particles move freely and spread out in all directions.
Diagram:
Draw particles spaced far apart.
Use arrows to show fast random movement in all directions.
Example:

markdown
Copy
* * *
* *
* *
Summary:
Solids: Tightly packed particles, fixed positions, only vibration.
Liquids: Close particles, can move past each other.
Gases: Widely spaced particles, fast and random motion.
These simple diagrams help to visually explain how particles behave differently in each state of matter!

Question 7

Explain the differences in density between the different
states of matter in terms of the arrangement of atoms or
molecules.

Answer 7

1. Solids:
   Arrangement of Particles: In solids, the particles (atoms or molecules) are tightly packed in a regular, fixed arrangement. They are held together by strong forces, so they vibrate in place but don’t move around.
   Density: Since the particles are closely packed, solids have a high density. The mass is concentrated in a small volume.
   Example: Lead, iron.
2. Liquids:
   Arrangement of Particles: In liquids, the particles are still close together, but they are not arranged in a fixed pattern. The forces between particles are weaker than in solids, allowing the particles to move past each other.
   Density: Liquids have a lower density than solids because although the particles are close, they have more space to move compared to solids. This means there’s less mass per unit volume.
   Example: Water, oil.
3. Gases:
   Arrangement of Particles: In gases, the particles are far apart and arranged randomly. The forces between the particles are very weak, allowing them to move freely and spread out in all directions.
   Density: Gases have a low density because the particles are spaced far apart, so the mass is spread over a larger volume.
   Example: Air, oxygen.
   Summary of Density Differences:
   Solids: Particles are tightly packed, leading to high density.
   Liquids: Particles are close but can move past each other, leading to lower density than solids.
   Gases: Particles are far apart, resulting in the lowest density.
   This difference in particle arrangement explains why solids are generally denser than liquids, and liquids are denser than gases.

Question 8

Describe how, when substances change state (melt,
freeze, boil, evaporate, condense or sublimate), mass is
conserved.

Answer 8

1. Melting (Solid to Liquid):
   Process: When a solid melts, it absorbs heat energy and the particles vibrate more, breaking free from their fixed positions but staying close together.
   Mass Conservation: The mass of the solid before melting is equal to the mass of the liquid after melting because the number of particles doesn’t change, only their arrangement.
2. Freezing (Liquid to Solid):
   Process: During freezing, a liquid loses heat and the particles slow down, moving closer together to form a solid structure.
   Mass Conservation: The mass of the liquid before freezing is equal to the mass of the solid after freezing. No particles are lost or gained in the process.
3. Boiling (Liquid to Gas):
   Process: When a liquid boils, it absorbs heat energy, and the particles gain enough energy to break free from the liquid and spread out as gas.
   Mass Conservation: The mass of the liquid before boiling is equal to the mass of the gas after boiling. The gas particles are just more spread out than the liquid particles, but the total number of particles (and mass) is conserved.
4. Evaporation (Liquid to Gas):
   Process: Evaporation happens at the surface of a liquid where particles gain enough energy to escape into the air as gas.
   Mass Conservation: The mass of the liquid before evaporation is equal to the mass of the gas afterwards. Some of the liquid evaporates, but the total mass remains unchanged, and the gas is still made of the same particles.
5. Condensation (Gas to Liquid):
   Process: When a gas cools down, its particles lose energy and move closer together, forming a liquid.
   Mass Conservation: The mass of the gas before condensation is equal to the mass of the liquid after condensation. The particles are simply rearranging, not disappearing.
6. Sublimation (Solid to Gas):
   Process: In sublimation, a solid skips the liquid state and directly turns into a gas (e.g., dry ice).
   Mass Conservation: The mass of the solid before sublimation is equal to the mass of the gas after sublimation. The particles turn directly into gas without passing through a liquid state, but the total mass remains the same.
   Summary:
   In all these changes of state, mass is conserved because the number of particles doesn’t change, just their arrangement or energy. Whether a substance melts, boils, freezes, evaporates, condenses, or sublimates, the total mass before and after the change is always the same.