1. STAR Testing Review
8th Grade Science
Structure of Matter
Periodic Table

2. Solids, Liquids and Gases
STATES OF MATTER!!!

3.  All matter is made of atoms and
molecules, which we will call particles.
 All particles vibrate or move because they
have energy.
 The state of matter they are in depends on
how strongly they are attracted to each
other.

4.  Matter that has defined shape and volume
is considered to be solid.
 Particles in a solid have high attraction for
each other. The particles vibrate in place
and don’t have enough energy to get away
from each other
 Two types of solids:
 Crystalline – particles in a repeating formation
 Amorphous – randomly oriented particles

5.  A solid has defined space and volume. It
will not take the shape of the container
unless energy is expended to make it a
different shape.

6.  Liquids have defined volume but not defined
shape
 The particles in a liquid can slide past each
other, and are less attracted to each other than in
a solid.
 Two properties of a liquid:
 Surface tension – the liquids tend to ball up and stick
together
 Viscosity – a measure of how well the liquid flows.
Water is low viscosity, molasses is high viscosity.

7.  A liquid has defined volume but will take
the shape of the container.
 They have more energy than a solid

8.  Gases have no defined shape or volume.
They can be compressed by pressure and
change their volume and will fill all the
space they are given.
 The particles in a gas are moving fast
enough to break away from each other and
each particle moves independently.
 In a gas, there is empty space between
particles.
 Pressure can effect all gases. High pressure
means that you have forced a large amount of
gas particles in a small space – like inside a
tire or basketball.
Gases

9. Phase Change!!!!
Solid--> Liquid--> Gas-->and back!

10. What IS phase change??
 Phase change is the change of the state (solid, liquid, gas)
that the matter is in.
 This change begins by either taking away energy or adding
energy to the particles of matter.
 These changes can start at any state and end at any state.

11. Melting!
 Melting involves ANY solid becoming a
liquid.
 Melting is ENDOTHERMIC- energy in the
form of heat is ENTERING the reaction.
 The molecules are gaining enough energy
to break away from their rigid structure and
move among the group.

12. Melting!
 Every substance has a “melting point”.
 The melting point is the temperature at
which the substance begins to melt.
 The melting point of a substance is a
physical property.
 **ALL substances have DIFFERENT
melting points! It’s not all the same as
water!!!!!!!

13. Freezing
 Freezing involves ANY liquid becoming
a solid.
 Freezing is an EXOTHERMIC reaction-
energy is EXITING the reaction in the
form of heat (heat is leaving).
 The molecules are losing energy- and
forced to stay in a rigid structure.

14. Freezing
 Every Substance has a “freezing point”
 The freezing point is the temperature
where the substance begins to freeze or
solidify.
 The freezing point of a substance is a
physical property and varies for each
substance.

15. Condensation
 Condensation is when a gas becomes a
liquid.
 This is an EXOTHERMIC reaction-
energy LEAVING in the form of heat.
 The molecules are losing energy and
become a group again after being totally
independent.

16. Vaporization
 Evaporation is any liquid becoming a gas
 This reaction is ENDOTHERMIC-
energy is ENTERING in the form of
heat!
 The molecules are gaining SO much
energy that they are becoming totally
independent and fly away on their own!

17. Vaporization
 There are two types:
 Boiling
 Evaporation

18. Boiling
 Boiling is…
 a relatively quick change from a liquid to a gas
 Occurs by adding a lot of heat all at once
 Happens at a specific temperature
 The change happens within the ENTIRE fluid-
all molecules are being affected.

19. Evaporation
 Evaporation is…
 A relatively slow process
 Occurs overtime from gas particles crashing
onto the surface of the liquid and passing on
their energy to the liquid molecules.
 No specific temperature associated with this
change (can happen at room temp!)
 Happens only on the surface of the liquid.

20.  Particles in a gas state are not bound to each
other and have the most energy.
Example of a Gas

21. The parts of an Atom

22. The atom
 An Atom: The most basic unit of matter.
 An atom has a dense nucleus and a cloud of
negatively charged electrons around it.
 If matter is what everything is made of, and
matter is made of atoms…
 Then, everything is really made of atoms!

23. The Parts:
 Electron: A subatomic particle with a negative
electrical charge. (no mass)
 Nucleus: The dense center of an atom
containing protons and neutrons.
 A Proton: A subatomic particle within the
nucleus of an atom that has a positive charge.
 A Neutron: A subatomic particle within the
nucleus of an atom that has a neutral charge.

24. Energy Level
 The energy level of an atom is as follows:
 2,8,8
 The first shell has two electrons
 The second shell has 8 electrons
 The third shell has 8 electrons
MEMORIZE: 2,8,8!!!!!!!!!!

25. Atomic Number
 The atomic number is the
number mainly associated
with the element and
represents the number of
protons present in the
atom.

26. Mass Number
 The total number of
protons and neutrons.
 The mass of an atom comes
from the protons and
neutrons.
 Therefore, the mass includes
the masses of each added
together.
 This number can be found at
the bottom, typically.
Mass Number

27. Element
 Each of these are ELEMENTS!!!
 When you put them together, they become
something different…

28. Compounds!
 Remember that compounds are merely the
result of combining two or more elements.
 H2O is a compound! NaCl is a compound!
 REMEMBER- compounds have different
properties than the elements they are made
of when alone.
 Hence why table salt (NaCl) doesn’t blow up

29. How can you identify Elements?
 What are the elements in the following
compounds?
 H2O
 NaCl
 CO2

30. Periodic Table!!
 Remember that beautiful display of
elements?
 It’s time to remember how to use it!

31. Time to test your knowledge!
 How many groups are there?
 Which group number are the noble (inert) gases?
 Why are the noble gases important?
 Where are the metals located?
 Where are the semi-metals?
 Where are the Alkali metals located?
 Where are the Alkaline Earth metals located?

33. Review of Chemical Bonding
Ionic, Covalent, Metallic

34. Ionic Bonds
 Ionic Bonds occur between metals and non-
metals.
 Metals always lose their extra valence
electrons and non-metals always try to gain
extra valence electrons.
 Metals become positive ions and non-
metals become negative ions.

35. Ionic Bonds
 Properties of Ionic Bonds:
 Brittle (breaks easily)
 Extremely high melting and boiling points
 Conduct electricity
 Form between ions (metals & non-metals)

36. Covalent Bonds
 Covalent bonds occur between non-metals
and non-metals
 Since non-metals are always trying to find
extra electrons rather than get rid of them,
Covalent bonds always share their electrons
(how nice of them!)

37. Covalent Bonds
 Properties of Covalent Bonds
 Malleable (can be formed/manipulated)
 Low melting and boiling points
 Do not conduct electricity or heat

38. Metallic Bonds
 Metallic bonds occur between metals and
metals.
 Remember that all metals are always trying
to lose their extra electrons to become
happy.
 In Metallic bonds metals “pool” their
electrons and all become ions while
“swimming” around in the pool of electrons
(AKA the “sea of negativity”)

39. Metallic Bonds
 Properties of Metallic Bonds:
 Malleable
 Ductile (can be stretched into wires)
 Conducts heat and electricity