chapter 2 part 1(08)
TRANSCRIPT
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