Biology Is Very Important

Formulation and testing of hypothesis

Hypothesis

    □ Tentative explanation that accounts for a set of facts and can be tested by further investigation
Diffusion
    □ Spontaneous process

    □ KE of the molecules and ions causes them to move from a region of high concentration to region of lower concentration

    □ Continues until it reaches equilibrium

..lab work

    □ Substances with lower MW diffuse faster than those with high MW.

    □ Heavier substances diffuse faster than the lighter ones.
    □
Diffusion tube set-up (gases)

    □ HCl and NH4OH
    □ HCl gas and NH3
    □ NH4Cl
  Table 1.   Distance of formation for     the NH4Cl ring

  NH4Cl ring formed closer to the containing HCl. Why?
    □ Ammonia must have diffused faster than HCl
    □ NH3 ( 17g/mol; HCl ( 36g/mol

    □ The rate of diffusion is affected by the mass of the particles

  Graham’s law of diffusion

    □ [pic]

    □ Under same T and P, the rates of diffusion for gaseous substances are inversely proportional to the square roots of their molecular masses

Agar-water gel method (liquids)

    □ Petri dish filled with agar-water gel
    □ 3 wells
    □ 3 substances:

    □ Rate of diffusion   is inversely proportional to the molecular weight of the substance

    □ At the same T, smaller molecules will move more rapidly than larger molecules because it takes more energy to get the larger molecule moving

    □ The greater the space bet molecules, the greater is its ability to spread, the greater is the rate of diffusion

Use of models
    □ Design or   structure which is a representative of some system
Uses
    □ Simplifies some technologically-limited system
    □ For better visualization of concepts, principles and systems
    □ Provides a logical framework of analysis

Hypothesis

    □ The cell membrane could allow some materials to pass through it while inhibiting others.

Responses of red blood cells
    □ NaCl...