States of Matter

1
States of Matter

• For molecular substances there are basically
  three states or phases of matter.
• Solids (s) Molecules are held in place by
  intermolecular interactions.
• Liquids (l) Molecules are held next to one
  another by noncovalent, intermolecular
  interactions, however, these interactions are not
  strong enough to prevent the molecules from
  flowing past one another.
• Gases (s) The intermolecular interactions are
  too weak to hold the molecules next to one
  another, so the molecules wander off on their own.

2
States of Matter
Water vapor, H2O(g)
Ice, H2O(s)
Liquid water, H2O(l)
3
States of Matter

• The strength and numbers of the noncovalent
  intermolecular interactions determine which state
  a molecular substance is in.
• The predominant noncovalent interaction between
  water molecules is the hydrogen bond

4
States of Matter

• These interactions can be disrupted by adding
  heat.
• Adding heat increases the kinetic energy of the
  molecules
• This is most readily observed with gases by
  looking at the Ideal Gas Law equation
• As the temperature of a gas increases, so does
  its kinetic energy.

5
States of Matter

• Ideal Gas Law Simulation

6
States of Matter

• A as heat is added to a molecular substance, it
  warms until reaching one of the phase transition
  temperature.
• At that point the heat (kinetic energy) that is
  added to the substance is used to break the
  noncovalent, intermolecular interactions.

7
States of Matter

• For a more detailed description of phase
  transitions, along with an animation of the
  process,see the Chem 150Elaboration - States of
  Matter

8
Enthalpy, Entropy and Free Energy

• Energy is defined as the ability to do work.
• The heat energy we have been talking about is
  also called Enthalpy (H)
• It was used to do the work of breaking the
  noncovalent, intermolecular interactions present
  in solids and liquids.
• When Enthalpy is put into an object, such as an
  ice cube, the change in Enthalpy for the ice cube
  increases.
• (?H gt 0). the ? symbol means change in.
• Changes in nature can be either spontaneous
  (favorable), or nonspontaneous (unfavorable).

9
Enthalpy, Entropy and Free Energy

• Why are some changes spontaneous while others are
  nonspontaneous?
• Why, like the ice on a pond, are changes
  spontaneous some of the time and nonspontaneous
  at other times?
• Asking some questions about the energy changes
  that take place can to help answer theses
  questions

10
Enthalpy, Entropy and Free Energy

• Changes occur spontaneously in nature when energy
  is released.
• The case of the rolling stone.

11
Enthalpy, Entropy and Free Energy

• Although Enthalpy is a form of energy, it alone
  cannot be used to answer these questions.
• The melting of the ice from a pond on a warm
  spring day is spontaneous
• However, the ice is absorbing heat (?? gt 0)
  (endothermic)
• A second factor called Entropy (S), needs to also
  be considered to determine if a change is
  spontaneous or nonspontaneous.

12
Enthalpy, Entropy and Free Energy

• Entropy is a measure of disorder.
• When ?S gt 0, things become more disorder.
• Nature prefers things to be disordered

13
Enthalpy, Entropy and Free Energy

• Enthalpy and Entropy can be combined to calculate
  another type of energy called Free Energy (G).
• ?G ?? - ??S
• The change in Free Energy can be used to predict
  whether a change is spontaneous or
  nonspontaneous.
• When ?G lt 0, the change is spontaneous
  (favorable)
• When ?G gt 0, the change is nonspontaneous
  (unfavorable)

14
Enthalpy, Entropy and Free Energy

• When Ice melts, ?H gt 0 and ?S gt 0
• It gains heat and becomes more disordered
• Above the freezing temperature, T?S gt ?H and ?G
  is negative ( ?G lt 0)
• Ice melts spontaneously.
• Below the freezing Temperature, T?S lt ?H and ?G
  is positive ( ?G gt 0)
• Ice does not melt spontaneously.

15
Enthalpy, Entropy and Free Energy

• When Ice freezes, ?H lt 0 and ?S lt 0
• It loses heat and becomes more ordered
• ?H makes a negative contribution to ?G
• ?S makes a positive contribution to ?G
• Below the freezing Temperature, the magnitude of
  T?S lt ?H and ?G is NEGATIVE (?G lt 0)
• Ice freezes spontaneously.
• Above the freezing temperature, the magnitude of
  T?S gt ?H and ?G is positive (?G gt 0)
• Ice freezes nonspontaneously.

16
Enthalpy, Entropy and Free Energy

• For a more detailed description using the
  enthalpy, entropy an free energy changes to
  predict if a process is spontaneous or not,see
  the Chem 150Elaboration - Ethalpy, Entropy
  Free Energy

17
Enthalpy, Entropy and Free Energy

• Figure 5.6, Raymond

?S lt 0 (molecules are more ordered)
?S gt 0 (molecules are more disordered)
18
Liquids

• Liquids have various physical properties that
  reflect the strength of the intermolecular
  interactions that hold the liquid together
• Boiling point temperature
• Viscosity
• Resistance to flow
• Vapor pressure

19
Liquids

• Viscosity
• Resistance to flow

20
Liquids

• Vapor Pressure and Boiling Points are related
• The boiling point is the temperature at which the
  vapor pressure is equal to the atmospheric
  pressure.

21
Liquids

• Vapor Pressure and Boiling Points are related
• The boiling point is the temperature at which the
  vapor pressure is equal to the atmospheric
  pressure.

22
Questions (Clickers)

• You planning to do some surgery on your kitchen
  table and know that you need to sterilize your
  instruments by heating them to 120C. You rummage
  around in the kitchen cupboards and find a
  pressure cooker that can heat water to a pressure
  of 1.4 atm. Will this be sufficient for
  sterilizing your instruments? (You may use Table
  5.6 in your book to answer this question see the
  previous slide.)
• Yes
• No
• Explain you answer.

23
Questions (Answer)

• 1.4 atm (760Torr/atm) 1064 Torr
• This is less than the pressure required to reach
  110C (1075 Torr), therefore it is an
  insufficient pressure to reach 120C.
• (120-100)/(125-100)(1741-760)7601544 Torr
  (interpolation)

24
Solutions

• Biological systems are mixtures of substances
• Pure substances contain only one type of element
  or compound
• They contain only one type of atom or molecule
• H2
• Hg
• O2
• H2O
• sucrose (C12H22O11)
• Mixtures contain more than one type of pure
  substance
• Heterogeneous mixture - components are not evenly
  mixed at the molecular level.
• Homogeneous mixture - components are evenly mixed
  at the molecular level.

25
Solutions

• A solution is another name for homogeneous
  mixture.
• Solvent - the major component in a solution
• Solute - the minor component in a solution.

26
Solutions

• A solution is another name for homogeneous
  mixture.
• Liquid solutions should be clear (transparent).
• Liquid solutions solutes should not settle with
  time
• This distinguishes solutions from suspensions
  and colloids.

27
Solutions

• In order form a solution to form
• the solute molecules have to be able to form
  similar noncovalent interactions with the solute
  molecules as
• the solute molecules form with themselves
• the solvent molecules form with themselves.

28
States of Matter

• Simulation of Glycerol and PropaneDissolving in
  Water

29
Solutions

• Solubility is a measure of how much solute will
  dissolve in a solvent.
• Solubility depends on temperature.
• The solubility of gases decrease with increasing
  temperature
• The solubility of solids and liquids usually
  increase with increasing temperature.

30
Solutions

• When a solution is saturated, the solute
  dissolves and precipitates at the same rate.

31
Solutions

• In order form a solution to form
• the solute molecules have to be able to form
  similar noncovalents with the solute molecules as
• the solute molecules form with themselves
• the solute molecules form with themselves.

32
Solubility of Gases in Water

• Henrys Law - The solubility of a gas in a liquid
  is proportional to the pressure of the gas over
  the liquid.
• The fizzing of soda when the cap is removed is an
  example of the lowered solubility of CO2 in water
  when its pressure above the soda is descrease.
• The solubility of CO2 in water is very high,
  because it can react with water to produce and
  even more soluble product, H2CO3 (carbonic acid)
• We will see that this is a very important
  reaction in biochemistry

33
Organic Compounds

• Nonpolar, organic solutes will dissolve readily
  in nonpolar, organic solvents.
• Like dissolves Like

34
Organic Compounds

• The solubility is determined by the balance
  between the polar and nonpolar portions of the
  molecule.

35
Biochemical Compounds Their Interactions with
Water

• Biological molecules are grouped into three
  categories.
• Hydrophilic (water loving) molecules.
• Polar molecules that can interact favorably with
  water
• Hydrophobic (water fearing) molecules.
• Nonpolar molecules that cannot interact favorably
  with water
• Amphipathic molecules, which are conflicted about
  their feelings towards water.
• Molecules containing both very polar and very
  nonpolar parts.

36
Biochemical Compounds Their Interactions with
Water

• Hydrophilic (water loving) molecules.
• Polar molecules that can interact favorably with
  water
• Carbohydrates (sugars) have lots of polar
  hydroxyl groups

37
Biochemical Compounds Their Interactions with
Water

• Hydrophilic (water loving) molecules.
• Polar molecules that can interact favorably with
  water
• Amino acids have both an amino and a carboxylic
  acid group, which are polar.

38
Biochemical Compounds Their Interactions with
Water

• Hydrophobic (water fearing) molecules.
• Nonpolar molecules that cannot interact favorably
  with water
• The carboxylic acid groups, though polar, are
  dominated by the long hydrocarbon portions

39
Biochemical Compounds Their Interactions with
Water

• Hydrophobic (water fearing) molecules.

• A nonpolar solute "organizes" water
• The H-bond network of water reorganizes to
  accommodate the nonpolar solute
• This is an increase in "order" of water-This is a
  decrease in ENTROPY

40
Biochemical Compounds Their Interactions with
Water

• Hydrophobic (water fearing) molecules.

41
Biochemical Compounds Their Interactions with
Water

• Amphipathic molecules, which are conflicted about
  their feelings towards water.
• Molecules containing both very polar and very
  nonpolar parts.

42
Biochemical Compounds Their Interactions with
Water

• When placed in water, amphipathic molecules, form
  structures, such as micelles, which attempt to
  address the conflict.

43
Colloids and Suspensions

• It is also possible to have mixtures which are
  not uniform at the molecular level.
• These are called heterogeneous mixtures.
• When a heterogenous mixture involves the mixing
  of a solid with a liquid, there are two possible
  situations
• Suspensions
• With time the solid settles out of the mixture
• Colloids
• The solid stays suspended in the liquid
  indefinitely,
• Both suspensions and colloids are cloudy.

44
Colloids and Suspensions
45
Diffusion and Osmosis

• Within a solution, the solute and solvent
  molecules are constantly moving
• If the concentration of the solute is not uniform
  throughout a solution, this movement will cause a
  net movement of solute molecules from the regions
  of high concentration to the regions of low
  concentration
• In the end the concentration will be the same
  everywhere.

46
Diffusion and Osmosis

• This movement is called diffusion.

47
Diffusion and Osmosis

• If a semipermeable membrane that only allows
  solvent to pass through it is used to separate a
  region of high solute concentration from a region
  of low solute concentration
• Solvent will move through the membrane from the
  region of low solute concentration to the region
  of high solute concentration in an effort to make
  the solute concentration the same on both sides
  of the membrane.

48
Diffusion and Osmosis

• This movement is called osmosis.

49
Diffusion and Osmosis

• This movement can be stopped by applying a
  pressure to the surface of the solution on the
  high solute concentration side of the membrane.
• The pressure required to stop the movement is
  called the osmotic pressure.

50
Diffusion and Osmosis

• Osmotic pressure is an important concept for
  understanding biological systems because the cell
  membrane is a semipermeable membrane
• If the solute concentrations are not equal on
  both sides of the membrane, the cells can either
  shrivel up or swell up and explode

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The End