1. Lecture 35 States of Matter Ozgur Unal
NIS – PHYSICAL SCIENCE
Lecture 35
States of Matter
Ozgur Unal

2. States of Matter
What are the states of matter?
Provide an example for each.
There are four states of matter:
Solid
Liquid
Gas
Plasma

3. States of Matter
In solid state the particles are packed closely together and constantly vibrating in place.
Strong attraction between
particles  fixed volume and shape
In liquid state, the attractive forces between particles are weaker than in a solid.
Particles can slide past each other.
Fixed volume, but indefinite shape.

4. States of Matter
In a gas, the particles are much farther apart than in a liquid or a solid  Weak attractive forces between particles.
No definite shape nor volume.
Gas particles diffuse much faster
than the ones in solids and liquids.
Plasma is matter consisting of
positively and negatively charged
particles  very energetic particles
No definite shape nor volume.
Example: Stars, auroras,
lightning bolts etc.

5. Changing States
Changes in the thermal energy of a material can cause it to change from one state to another.
Changing from solid to liquid  Melting
Changing from liquid to solid  Freezing
Changing from liquid to gas  Vaporization
Changing from gas to liquid  Condensation
During melting the energy of the
particles in a solid increases.
The energy of the particles becomes
high enough to overcome the
attractive forces between the particles.
The particles can slip out of their
ordered arrangement.

6. Melting and Freezing
During melting the energy of the particles in a solid increases, which becomes high enough to overcome the attractive forces between the particles.
The particles can slip out of their ordered arrangement.
The temperature at which a solid begins to melt is its melting point.
The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the heat of fusion.
Lf (water)= 334 J/g
Heat of fusion is also the energy released
during freezing.

7. Vaporization and Evaporation
As the temperature of a liquid increases, the particles move faster, eventually the particles become very energetic enough to overcome the attractive force of other particles  Vaporization
Vaporization that occurs at the surface of a liquid is called evaporation.
Why do we sweat when it is hot?

8. Boiling A second way that a liquid can vaporize is by boiling.
Boiling occurs throughout a liquid at a certain temperature depending on the air pressure at the surface of the liquid.
The boiling point of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface.
The heat of vaporization is the
amount of energy required for 1 kg
of the liquid at its boiling point to
become a gas.
Lv (water)= 2260 J/g

9. Condensation
The heat of vaporization is also the amount of energy released during condensation, when a gas changes into a liquid.
Dew is also the result of condensation.
Dew forms when the air around matter, such as spider webs, cools enough so that water vapor in the air changes to a liquid.

10. Heating Curve of a Substance
The graph below shows the heating curve of water.
Why is the temperature constant during melting and boiling?

11. Lecture 36 Thermal Expansion Ozgur Unal
NIS – PHYSICAL SCIENCE
Lecture 36
Thermal Expansion
Ozgur Unal

12. Thermal Expansion
An object (whether solid, liguid, gas or plasma) expands as it gets hotter.
According to the kinetic theory, the particles in an object move faster as the temperature increases.
As they move faster, their motion can overcome the attractive forces between particles and the distances between particles increase  The object expands
Similarly, decreasing temperature leads to
contraction of objects.

13. Thermal Expansion of Solids
Solids expand with increasing temperature.
Expansion occurs in 3 dimensions.
The amount of expansion in one dimension can be calculated according to the following formula:
ΔL = L * α * (Tf - Ti)
L is the initial length of one side of the solid
ΔL is the amount of expansion
Ti (Tf) is the initial (final) temperature of the solid
α is the coefficient of linear expansion, which depends on the type of solid.

14. Thermal Expansion of Liquids and Gases
Liquids also expand as they get
hotter  Increase in volume
Example: Alcohol thermometer
Gases expand even more than solids and liquids when the temperature increases  Increase in volume
For a given amount of gas, an increase in
volume means a decrease in the density.
Example: Hot air balloon