## Three States of Matter – Structured Question 1

Structure Question 1:

The above diagram shows the apparatus used in an experiment to determine the freezing point of liquid naphthalene. The liquid naphthalene is cooled from 100°C in a conical flask and it is stirred continuously with a thermometer. The temperature of liquid naphthalene is recorded in every 30 seconds. The results obtained are tabulated below:

 Time (s) 0 30 60 90 120 150 Temperature (oC) 100 93 85 78 78 78
 Time (s) 180 210 240 270 300 Temperature (oC) 78 60 43 25 25

1. Draw a graph of temperature against time for the cooling of liquid naphthalene. [2 marks]
 (Click on the image to enlarge)
2. Determine the freezing point of liquid naphthalene from the graph.
78°C
3. c.What is the physical state of naphthalene at
1. 60s
liquid
2. 120s
liquid and solid
3. 180s
solid
4. Draw the particles arrangement of naphthalene at c.i. and  c.iiic. i.

c. ii.

5. Explain why the temperature remains constant between 3 and 6 minutes?
From the time 90 second to 180 seconds, naphthalene is freezing. During freezing, bonds are formed in between the molecules and energy is released. The energy lost to the surrounding is compensated by the energy released from the formation of the bonds.
6. Explain why the boiling tube is placed inside a conical flask during the cooling process.
To ensure constant cooling at a slow rate for naphthalene. This can avoid supercooling.
7. Give a reason why naphthalene needs to be stirred continuously during the process?
To avoid supercooling.
8. Will the melting point of naphthalene differ if it is contaminated by other substance?
Yes
9. Sketch a graph obtained when solid naphthalene is heated from room temperature (25°C) to 100°C.

## Objective Question s Practice 1

1. Which of the following substances sublimes at room pressure when heated?
1. Iodine
2. Dry ice (Solid carbon dioxide)
3. Naphthalene
4. Ammonium Chloride
2. Which of the following take place when water solidifies to become ice?
1. Energy is absorbed from the surrounding.
2. Water molecules get nearer to each other.
3. Water molecules are not arranged orderly.
4. The mass increase.

## Symbol of Elements

A symbol of element is the chemical symbol written in short form to represent a particular element. Some elements are represented by the first letter of its name.

Examples:

 Element Symbol Fluorine F Hydrogen H Iodine I Nitrogen N Oxygen O Phosphorus P Sulphur S Carbon C Vanadium V

If there are two or more elements that have mane start with the same alphabet letter, a second letter is added to differentiate between these elements. The second letter used is always lowercase.
Examples:

 Elements Symbol Bromine Br Calcium Ca Chlorine Cl Chromium Cr Magnesium Mg Manganese Mn Neon Ne Nickel Ni Silicon Si Helium He Argon Ar Aluminium Al Zinc Zn Platinum Pt

Some elements are represented by their Latin names.
Example:

 Elements Latin Name Symbol Copper Cuprum Cu Iron Ferrum Fe Lead Plumbum Pb Mercury Hydrargyrum Hg Potassium Kalium K Silver Argentum Ag Sodium Natrium Na Tin Stannum Sn

(Notes: You MUST Memorise the symbol for all these 31 elements)

## Brownian Motion

1. Brownian motion is the physical phenomenon that tiny particles immersed in a fluid move about randomly.
2. A fluid can be a liquid or a gas.
3. Brownian movement, an example of diffusion, supports the kinetic theory of matter.
4. Examples of Brownian movement are
1. movement of smoke particles in air
2. movement of pollen grains in water

## Diffusion in Gas

 (Diffusion in Gas)
Observation

The brown colour bromine vapour spreads evenly throughout the gas jar in a few minutes

• Bromine vapour is made of tiny and discrete molecules that move randomly to fill up space.
• Bromine vapour moves randomly and diffuses in all directions in air from areas of higher concentration to areas of lower concentration.
Conclusion :
The rate of diffusion is highest in gas and lowest in solid.

## Diffusion in Liquid

### Diffusion in Liquid

 (Diffusion in Liquid)
Observation
The purple colour of potassium manganate(VII) fills up the entire test tube after a few hours
• Diffusion has taken place in the liquid.
• The rate of diffusion of the particles in water is faster than the diffusion rate of particles in solid.
• The occurrence of diffusion proves that potassium permanganate(VII) consist of tiny and discrete particles.

## Diffusion in Solid

 Diffusion in Solid
Observation

The blue colour of copper(II) sulphate fills up the entire test tube after a few days

• Copper(II) sulphate crystals are made of copper(II) ions and sulphate ions which are tiny and discrete.
• The particles in the copper(II) sulphate crystal will separate to become ions and diffuse randomly upwards until the whole agar turns blue.

## Diffusion and Brownian Motion

### Proof of Particle Theory of Matter – Diffusion

In SPM, you need to know
1. diffusion is one of the proofs of the particle theory of matter.
2. the definition of diffusion.
3. diffusion in solid, liquid and gas
4. factors that affect the rate of diffusion and the related experiments.

### What is Diffusion?

1. Diffusion is a process of spreading a substance from a region of high concentration to a region of low concentration.
2. It occurs when the particles of the substance move through the space between the particles of another substance.
3. Figure below shows how the bromine particles diffuse into the air.
4. Diffusion occurs in solid, liquid and gas.
5. The rate of diffusion is highest in gas and lowest in solid.
6. Diffusion is proof of the particle theory of matter.
MUST KNOW!
• The rate of diffusion is highest in gas and lowest in solid.
• Diffusion is the proof of the particle theory of matter.

## Particulate Nature of Matter

1. Matter is anything that occupies space and has mass.
2. The particle theory of matter states that matter is made up of a large number of tiny and discrete particles.
Particle Theory of Matter:  Matter is made up of a large number of tiny and discrete particles.

## Types of Particles

1. Particles can exist as atoms, molecules or ions.
2. Atom is the smallest, indivisible particle of an element.
3. Molecules are particles that made up of two or more atoms.
4. Ions are particles that carry charge.
1. Positive ion – Cation
2. Negative ion – Anion