Part 7 Flashcards
Physical Properties of Substances
Are observable characteristics that change without modifying the identity of the substance
one example is state of matter: liquid, solid, and gas.
Hydrogen
when two atoms of hydrogen and an oxygen atom combine, they form a water molecule, a substance that is liquid at room temp.
at room temperature hydrogen and oxygen are both gases
Boiling Point
temperature at which a substance boils, changing its state from liquid to gas
Melting point
is a constant that is indicative of substance
Quantity of a substance
The quantity of a substance is taken into account when considering the amount of energy needed to bring the substance toward either of these point
Specific Heat Capacity
Is a measure of the amount of energy needed to change the temperature of 1 gram of a substance by 1 degree celsius.
But both boiling and melting point are the results of intermolecular forces and therefore are independent of the quantity of the substance.
Intensive Properties
physical properties that are independent of the amount of substance present
for an atom of an element or a molecule made of one different elements, intensive properties can be assessed for substance identification.
ex: Luster, conductivity, malleability, and density are other intensive properties
Extensive Properties
Are those characteristics of a substance that depend on the size of a sample like length, volume, mass and energy, enthalpy, and entropy.
Independently, volume and mass cannot be used for substance identification, but density can because it takes both size and mass of a substance sample into account and its constant for each substance.
Chemical Properties
Are a function of chemical reactivity of the substance
these characteristics control how one substance can be changed into another substance
the change in composition of a substance incorporates the breaking or creation of bonds.
Properties role in biological systems
The physical and chemical property of a substance affects its role in biological systems.
a substance’s properties determine the kinds of bonds it will form with other substances
waters unique properties and development of diffusion gradients that drive osmosis results from physical and chemical properties of the substances involved.
Polar Bonds and Nonpolar Covalent Bonds
Depending on the substances involved, covalent bonds can be either polar or non polar.
If and where polar or non polar covalent bonds form in a substance influences whether a region of a molecule has partial charges.
Partial charges on regions of a molecule make it attracted to or repulsed by other substances with partial or full charges.
Hydrogen Bond
is a weak bond formed between the partial negative region of one oxygen atom and partial positive region of a hydrogen atom.
How water sticks?
Hydrogen bonds between the partial positively charged hydrogen atom of one water molecule and the partially negatively charged oxygen atom of another water molecule makes water stick to itself through cohesion and to other molecules through adhesion.
Cohesion
Cohesion creates surface tension, and cohesion together with adhesion are behind the capillary action that moves water up plant xylem.
Breaking up the multitude of hydrogen bonds between water requires a lot of energy, so water is said to have a specific heat capacity.
Water and solid density
Another unusual property of water that is due to hydrogen bonds is that liquid water is denser than solid water.
Ice floats on water because more hydrogen bonds form between water with lower kinetic energy
these intermolecular bonds maintain individual water molecules at a greater distance than they would be without as many hydrogen bonds
Diffusion
is the passive movement of a substance from areas of high concentration to low concentration.
Ions Movement
Ions are unable to pass through the lipid bilayer of a cell membrane so their movement into or out of a cell depends on specialized ion channels on the membrane.
some of these channels have the ability to pump ions against their concentration gradients
osmosis
is the diffusion of water across a semipermeable membrane such as a cell membrane
like ions, water does not move easily through the cell membrane’s lipid bilayer
Osmosis doesn’t require the cell to use any energy for its transport, but for water or other substances to move from areas of low to high concentrations, energy must be expended by the cell.