CHAPTER 2

The Structure of the Atom

What is a matter?

Matter is defined as anything that has

mass and takes up space.

Can you define the word ‘mass’?

Mass

The mass of an object is the amount of matter the object contains.

A golf ball has a greater mass than a tennis ball.

The golf ball, therefore, contains more matter.

What is matter made up of ?

Matter

Particles

IonsMoleculesAtoms

is the smallest neutral particles in an elementFor example : Copper, Cu, Oxygen, O

are neutral particles made up of two or more atoms of the same element or different elementsOxygen gas, O2

Carbon dioxide gas, CO2

Ions are particles which are positively or negatively charged+ve ions cations, -ve ions anions

+ -

• matter is made up of particles which are constantly moving and contain kinetic energy

• The random movement of particles in air is called the Brownian Movement

Kinetic Theory of Matter

Diffusion• is the movement of particles at random from

highly concentrated area to a less concentrated area

• Gases, liquids and solids contain air spaces with gases containing the most and solid containing the least

• The presence of these empty spaces allow the diffusion of gases, liquids and solids through them

> >

• Do you know why we can smell a durian kept in the corner of a room ?

• Its smell diffuses rapidly through air which has more empty spaces than liquids and solids

Diffusion of particles in a gas, liquid and solid

The particles in aThe particles in a solid are packed solid are packed lightly in a fixed pattern. There are lightly in a fixed pattern. There are

strong forces holding them together, strong forces holding them together, so they cannot leave their positions. so they cannot leave their positions. The only movements they make are The only movements they make are

tiny vibrations to and fro.tiny vibrations to and fro.

The particles in a liquid can move The particles in a liquid can move about and slide past each other. They about and slide past each other. They are still close together but are not in a are still close together but are not in a

fixed pattern. The forces that hold fixed pattern. The forces that hold them together are weaker than in a them together are weaker than in a

solid.solid.

The particles in a gas are far apart, and The particles in a gas are far apart, and they move about very quickly. There are they move about very quickly. There are almost no forces holding them together. almost no forces holding them together. They collide with each other and bounce They collide with each other and bounce

off in all directions.off in all directions.

Solid

Liquid

GasM

eltin

g

Free

zing

Boiling/

EvaporationCondensation

Sublimation

Sublimation

Melting• When a solid is heated, its particles get

more energy and vibrate more. This makes the solid expand. At the melting point, the particles vibrate so much that they break away from their positions. The solid becomes a liquid.

Boiling• When a liquid is heated, its particles get

more energy and move faster. They bump into each other more often and bounce further apart. At the boiling point, the particles get enough energy to overcome the forces holding them together. They break away from the liquid and form a gas

Evaporation• Some particles in a liquid have more

energy than others. Even when a liquid is well below boiling point, some particles have enough energy to escape and form a gas. It is why puddles of rain dry up in the sunshine.

Condensation• When a gas is cooked, the particles lose

energy. They move more and more slowly. When they bump into each other, they do not have enough energy to bounce away again. They stay close together and a liquid forms. When the liquid is cooled, the particles slow down even more. Eventually they stop moving, except for tiny vibrations, and a solid forms.

Sublimation• Is a process during which a solid gains

enough energy to overcome the forces of attraction between its particles to become a gas, without going through the liquid state, and vice versa

Determining the melting point of acetamide

Heating of acetamide3 spatula of acetamide are placed in a boiling tube

A 250 ml beaker is filled with water and then placed on a tripod stand

The boiling tube is clamped in the beaker and make sure the acetamide is below the water level of the water bath

The water bath is heated until reach a temperature about 65 0C, a stop watch is started and the water is then heated with a low flame

The temperature of acetamide is recorded at 30 s intervals until 90 0C.

Make sure the acetamide is stirred continuously during the experiment

The result are recorded in a table

Cooling of acetamideThe boiling tube id removed from the hot water bath using test tube holder

It id immediately transferred into a conical flask to be cooled slowly and then the stop watch is started

The temperature is recorded at 30 s intervals until 70 0C

Make sure the acetamide is stirred continuously during the experiment

The result are recorded in a table