Physical and Chemical Properties

1
Chapter 3

• Physical and Chemical Properties
• Physical and Chemical Changes

2
Physical Properties

• Physical properties can be observed or measured
  without changing the composition of matter.
  Physical properties are used to observe and
  describe matter.
• Physical properties include appearance, texture,
  color, odor, melting point, boiling point,
  density, solubility, polarity, and many others.
• NOT RELATED TO INTERACTION WITH OTHER MATERIALS

3
What physical properties can you observe?
4
Physical Properties of Magnesium

• Description
• Grayish-white metal.
• Atomic Mass Average 24.305 amu
• Boiling Point 1363K 1090C 1994F
• Conductivity
• Density 1.738g/cm3
• Enthalpy of Fusion 8.95 kJ/mole
• Melting Point 922K 649C 1200F
• Molar Volume 13.97 cm3/mole
• Physical State (at 20C 1atm) Solid
• Specific Heat 1.02J/gK

5
Chemical Properties

• Chemical properties of matter describes its
  "potential" to undergo some chemical change or
  reaction by virtue of its composition.
•  It is quite difficult to define a chemical
  property without using the word "change".
  Eventually you should be able to look at the
  formula of a compound and state some chemical
  property. At this time this is very difficult to
  do and you are not expected to be able to do it.

6
Chemical Properties

• Reactivity is really the only chemical
  property. Anything that describes how a
  substance reacts is a chemical property.
• For example hydrogen has the potential to ignite
  and explode given the right conditions. This is a
  chemical property.
• Metals in general have they chemical property of
  reacting with an acid. Zinc reacts with
  hydrochloric acid to produce hydrogen gas. This
  is a chemical property.

7
Chemical Properties

• A chemical property of magnesium is that it
  reacts with carbon dioxide producing an intense
  light.

Magnesium reacting with dry ice.
8
Physical Changes

• A physical change takes place without any changes
  in composition. The same element or compound is
  present before and after the change.

9
Chemical Changes or Reactions

• Chemical changes result in one or more substances
  of entirely different composition from the
  original substances. The elements and/or
  compounds at the start of the reaction are
  rearranged into new compounds or elements.
• Magnesium reacts with oxygen from the air
  producing an extremely bright flame. This is a
  chemical change since magnesium oxide has
  completely different properties than magnesium
  metal or oxygen.
• The atoms are rearranged - diatomic oxygen
  molecules are split apart so that one oxygen atom
  combines with one magnesium atom.

10
(No Transcript)
11
PHYSICAL CHANGE CHEMICAL CHANGE
Do not change the chemical makeup of the changed material Result in a new material with a different chemical makeup being formed
Change only the physical properties of a material Change both physical and chemical properties of a material
relatively simple to reverse very difficult to reverse
Look to be fairly simple changes Look more dramatic
Not Likely to be accompanied by changes in color, temperature, state (unforced), or smell. Often accompanied by change in color, temperature, state ( unforced), or smell.
12
Changes of State are physical changes but can
accompany a chemical change

• Physical Change

• Chemical Change

Precipitate
13
Precipitate

• A solid insoluble substance that forms when
  solutions are mixed.

14
Distillation

• Distillation is used to purify a compound by
  separating it from a non-volatile or
  less-volatile material. When different compounds
  in a mixture have different boiling points, they
  separate into individual components when the
  mixture is carefully distilled.

15
Distillation

• Distillation is used to purify a compound by
  separating it from a non-volatile or
  less-volatile material. When different compounds
  in a mixture have different boiling points, they
  separate into individual components when the
  mixture is carefully distilled.
• Distillation is the process of heating a liquid
  until it boils, capturing and cooling the
  resultant hot vapors, and collecting the
  condensed vapors.

16
Distillation

• Distillation is used to purify a compound by
  separating it from a non-volatile or
  less-volatile material. When different compounds
  in a mixture have different boiling points, they
  separate into individual components when the
  mixture is carefully distilled.
• Distillation is the process of heating a liquid
  until it boils, capturing and cooling the
  resultant hot vapors, and collecting the
  condensed vapors.
• Mankind has applied the principles of
  distillation for thousands of years. Distillation
  was probably first used by ancient Arab chemists
  to isolate perfumes evidence of which dates back
  to 3500 BC.

17
Distillation

• Distillation is used to purify a compound by
  separating it from a non-volatile or
  less-volatile material. When different compounds
  in a mixture have different boiling points, they
  separate into individual components when the
  mixture is carefully distilled.
• Distillation is the process of heating a liquid
  until it boils, capturing and cooling the
  resultant hot vapors, and collecting the
  condensed vapors.
• Mankind has applied the principles of
  distillation for thousands of years. Distillation
  was probably first used by ancient Arab chemists
  to isolate perfumes evidence of which dates back
  to 3500 BC.
• In the modern organic chemistry laboratory,
  distillation is a powerful tool, both for the
  identification and the purification of organic
  compounds.

18
(No Transcript)
19
Fractional Crystallization

• Separates different solutes from a solution based
  on differences in their solubility.
• A process by which a chemical compound is
  separated into components by crystallization. In
  fractional crystallization the compound is mixed
  with a solvent, heated, and then gradually cooled
  so that, as each of its constituent components
  crystallizes, it can be removed in its pure form
  from the solution.

20
(No Transcript)
21
What is the solubility of KNO3 at 80ºC?
22
At what temperature is the solubility of KBr
equal to 60g/100g H2O?
23
Example of Fractional Crystallization

• The solubility of compounds changes with
  temperature, and different compounds will respond
  differently to a decrease in temp.  For example,
  if compound A is soluble at 30 to 35ºC, but
  compound B is insoluble at 30 to 35ºC, and if
  they are both soluble at 50ºC, then what happens
  if you lower the temperature of a mixture of the
  two solutions from 50 to 30ºC?

24
Example of Fractional Crystallization

• The solubility of compounds changes with
  temperature, and different compounds will respond
  differently to a decrease in temp.  For example,
  if compound A is soluble at 30 to 35ºC, but
  compound B is insoluble at 30 to 35ºC, and if
  they are both soluble at 50ºC, then what happens
  if you lower the temperature of a mixture of the
  two solutions from 50 to 30ºC?Answer Compound
  A will still be in solution, but compound B will
  have precipitated (crystallized).

25
Homework

• Chap 3 Worksheet 3-1