Thursday, January 10, 2008
Thurs-Day 1
Hey, scientists bring good news today to those of us (like me) who unduly fear needles
or IV devices; read on: http://www.sciencedaily.com/releases/2008/01/080107143001.htm
Bio- we discussed the functions of the rest of the endocrine system glands:
parathyroids- we drew out the negative feedback loop by which the parathyroids regulate the concentration of calcium ions in the blood.
adrenals- adrenaline is secreted when a person is under high stress from the environment (internal or external) so that the person can effectively fight or flee the situation.
adrenal glands also secrete hormones that regulate the concentration of water and sodium ions in the blood by targeting kidney cells.
We discussed the sex hormones secreted from the ovaries (females) and testes (males):
the menstrual cycle, involving the periodic thickening of the uterus and the maturation and release of an egg cell is regulated by pituitary hormones and ovary hormones (estrogen and progesterone); also, secondary sex characteristics develop as a result of the secretion of sex hormones: in females, breast development and skeletal changes such as the broadening of the pelvis occur; in males, testosterone causes more facial and body hair to grow and/or thicken, muscles to develop, the larynx to become thicker and more developed (deeper voice).
We then focused on the all-important negative feedback loop:
negative feedback is a key feature of the endocrine system that helps an organism maintain homeostasis. In general,
a deficiency of some substance "X" is monitored and detected by some gland "G"--> the gland then secretes a hormone "H" which targets specific cells which then are signaled to make more of substance "X" (increasing the level of substance "X" in the blood) so that there is no more deficiency; (now for the NEGATIVE feedback part) the normal/increased level of substance "X" in the blood causes gland "G" to STOP secreting hormone "H" (otherwise the level of substance "X" may get TOO HIGH!) thus completing the feedback loop and maintaining homeostasis.
Chem 7- I put up some practice test questions with answers on Blackboard. THIS UNIT requires MORE practice than ANY other unit in chemistry. You NEED to do as many problems as possible in order to be prepared for the exam on Wednesday.
we repeated that molecules that have a lone pair or pairs of electrons CAN FORM a coordinate covalent bond (with H+, for example) BUT any POLYATOMIC ION, like NH4+ or H3O+ already HAS a coordinate covalent bond!
We discussed how metal atoms bond to each other, which is called, naturally, metallic bonding.
Metal atoms have too few valence electrons to form an octet between two atoms so they mutually share their valence electrons in a lattice of positive metal nuclei. Each valence electron is only weakly attracted to any one nucleus (low Zeff) so the valence electrons are relatively free to flow throughout the lattice, which is why metals are good electrical conductors. All of the mutual attractions between all neighboring valence electrons and their neighboring positive nuclei make metallic bonds very strong.
We looked at the THREE different types of INTERmolecular attractions. BY DEFINITION, INTER means BETWEEN and molecular means molecules, so intermolecular attractions are NOT BONDS!!! They are merely the attractions BETWEEN the PARTIALLY positively charged side of one molecule and the PARTIALLY negatively charged side of a NEARBY separate molecule. There is NO sharing of electrons, there are NO fully charged IONS. End of story.
So,
(1) NONPOLAR MOLECULES can only form the weakest of intermolecular attractions (London Dispersion/Van der Waals/induced dipole) because any dipoles that form are random and short-lived.
(2) POLAR MOLECULES form stronger intermolecular attractions between their permanent dipoles ( attraction of the partial positive side of one molecule to the partial negative side of another molecule); these attractions are called DIPOLE-DIPOLE attractions.
(3) EXTREMELY POLAR MOLECULES:
Molecules that have H covalently bonded to F, O, or N are extremely polar. There is such unequal sharing of electrons between the (low electronegativity:2.1) H and the highly electronegative F,O, or N (4.0, 3.5, and 3.0) that the molecule has most of its electrons on ONE SIDE of the molecule (by F, O, or N) most of the time. Therefore, an EXTREME partial negative charge is permanently near the F, O, or N part of the molecule and an EXTREME partial positive charge is near the H part(s) of the molecule. So separate molecules will have EXTREME DIPOLE-DIPOLE attractions causing the molecules to stay near each other even at high avg KE (near room temperature). Classic examples of molecules that have these EXTREME DIPOLE-DIPOLE attractions that, confusingly, are called "hydrogen bonding" attractions (even though NO COVALENT BONDS EXIST BETWEEN ANY TWO DIFFERENT MOLECULES!) are H2O, NH3, and HF. Sorry, we just have to live with the name "hydrogen bonding" and make sure that we NEVER confuse it with a covalent bond WITHIN a molecule between H and another atom. In fact, any covalent bond between H and any other atom is about 500 times stronger than a "hydrogen bonding" attraction between separate molecules.
Chem 8/9- I put up some practice test questions with answers on Blackboard. THIS UNIT requires MORE practice than ANY other unit in chemistry. You NEED to do as many problems as possible in order to be prepared for the exam on Wednesday.
we repeated that molecules that have a lone pair or pairs of electrons CAN FORM a coordinate covalent bond (with H+, for example) BUT any POLYATOMIC ION, like NH4+ or H3O+ already HAS a coordinate covalent bond!
We discussed how metal atoms bond to each other, which is called, naturally, metallic bonding.
Metal atoms have too few valence electrons to form an octet between two atoms so they mutually share their valence electrons in a lattice of positive metal nuclei. Each valence electron is only weakly attracted to any one nucleus (low Zeff) so the valence electrons are relatively free to flow throughout the lattice, which is why metals are good electrical conductors. All of the mutual attractions between all neighboring valence electrons and their neighboring positive nuclei make metallic bonds very strong.
We looked at the THREE different types of INTERmolecular attractions. BY DEFINITION, INTER means BETWEEN and molecular means molecules, so intermolecular attractions are NOT BONDS!!! They are merely the attractions BETWEEN the PARTIALLY positively charged side of one molecule and the PARTIALLY negatively charged side of a NEARBY separate molecule. There is NO sharing of electrons, there are NO fully charged IONS. End of story.
So,
(1) NONPOLAR MOLECULES can only form the weakest of intermolecular attractions (London Dispersion/Van der Waals/induced dipole) because any dipoles that form are random and short-lived.
(2) POLAR MOLECULES form stronger intermolecular attractions between their permanent dipoles ( attraction of the partial positive side of one molecule to the partial negative side of another molecule); these attractions are called DIPOLE-DIPOLE attractions.
(3) EXTREMELY POLAR MOLECULES:
Molecules that have H covalently bonded to F, O, or N are extremely polar. There is such unequal sharing of electrons between the (low electronegativity:2.1) H and the highly electronegative F,O, or N (4.0, 3.5, and 3.0) that the molecule has most of its electrons on ONE SIDE of the molecule (by F, O, or N) most of the time. Therefore, an EXTREME partial negative charge is permanently near the F, O, or N part of the molecule and an EXTREME partial positive charge is near the H part(s) of the molecule. So separate molecules will have EXTREME DIPOLE-DIPOLE attractions causing the molecules to stay near each other even at high avg KE (near room temperature). Classic examples of molecules that have these EXTREME DIPOLE-DIPOLE attractions that, confusingly, are called "hydrogen bonding" attractions (even though NO COVALENT BONDS EXIST BETWEEN ANY TWO DIFFERENT MOLECULES!) are H2O, NH3, and HF. Sorry, we just have to live with the name "hydrogen bonding" and make sure that we NEVER confuse it with a covalent bond WITHIN a molecule between H and another atom. In fact, any covalent bond between H and any other atom is about 500 times stronger than a "hydrogen bonding" attraction between separate molecules.
or IV devices; read on: http://www.sciencedaily.com/releases/2008/01/080107143001.htm
Bio- we discussed the functions of the rest of the endocrine system glands:
parathyroids- we drew out the negative feedback loop by which the parathyroids regulate the concentration of calcium ions in the blood.
adrenals- adrenaline is secreted when a person is under high stress from the environment (internal or external) so that the person can effectively fight or flee the situation.
adrenal glands also secrete hormones that regulate the concentration of water and sodium ions in the blood by targeting kidney cells.
We discussed the sex hormones secreted from the ovaries (females) and testes (males):
the menstrual cycle, involving the periodic thickening of the uterus and the maturation and release of an egg cell is regulated by pituitary hormones and ovary hormones (estrogen and progesterone); also, secondary sex characteristics develop as a result of the secretion of sex hormones: in females, breast development and skeletal changes such as the broadening of the pelvis occur; in males, testosterone causes more facial and body hair to grow and/or thicken, muscles to develop, the larynx to become thicker and more developed (deeper voice).
We then focused on the all-important negative feedback loop:
negative feedback is a key feature of the endocrine system that helps an organism maintain homeostasis. In general,
a deficiency of some substance "X" is monitored and detected by some gland "G"--> the gland then secretes a hormone "H" which targets specific cells which then are signaled to make more of substance "X" (increasing the level of substance "X" in the blood) so that there is no more deficiency; (now for the NEGATIVE feedback part) the normal/increased level of substance "X" in the blood causes gland "G" to STOP secreting hormone "H" (otherwise the level of substance "X" may get TOO HIGH!) thus completing the feedback loop and maintaining homeostasis.
Chem 7- I put up some practice test questions with answers on Blackboard. THIS UNIT requires MORE practice than ANY other unit in chemistry. You NEED to do as many problems as possible in order to be prepared for the exam on Wednesday.
we repeated that molecules that have a lone pair or pairs of electrons CAN FORM a coordinate covalent bond (with H+, for example) BUT any POLYATOMIC ION, like NH4+ or H3O+ already HAS a coordinate covalent bond!
We discussed how metal atoms bond to each other, which is called, naturally, metallic bonding.
Metal atoms have too few valence electrons to form an octet between two atoms so they mutually share their valence electrons in a lattice of positive metal nuclei. Each valence electron is only weakly attracted to any one nucleus (low Zeff) so the valence electrons are relatively free to flow throughout the lattice, which is why metals are good electrical conductors. All of the mutual attractions between all neighboring valence electrons and their neighboring positive nuclei make metallic bonds very strong.
We looked at the THREE different types of INTERmolecular attractions. BY DEFINITION, INTER means BETWEEN and molecular means molecules, so intermolecular attractions are NOT BONDS!!! They are merely the attractions BETWEEN the PARTIALLY positively charged side of one molecule and the PARTIALLY negatively charged side of a NEARBY separate molecule. There is NO sharing of electrons, there are NO fully charged IONS. End of story.
So,
(1) NONPOLAR MOLECULES can only form the weakest of intermolecular attractions (London Dispersion/Van der Waals/induced dipole) because any dipoles that form are random and short-lived.
(2) POLAR MOLECULES form stronger intermolecular attractions between their permanent dipoles ( attraction of the partial positive side of one molecule to the partial negative side of another molecule); these attractions are called DIPOLE-DIPOLE attractions.
(3) EXTREMELY POLAR MOLECULES:
Molecules that have H covalently bonded to F, O, or N are extremely polar. There is such unequal sharing of electrons between the (low electronegativity:2.1) H and the highly electronegative F,O, or N (4.0, 3.5, and 3.0) that the molecule has most of its electrons on ONE SIDE of the molecule (by F, O, or N) most of the time. Therefore, an EXTREME partial negative charge is permanently near the F, O, or N part of the molecule and an EXTREME partial positive charge is near the H part(s) of the molecule. So separate molecules will have EXTREME DIPOLE-DIPOLE attractions causing the molecules to stay near each other even at high avg KE (near room temperature). Classic examples of molecules that have these EXTREME DIPOLE-DIPOLE attractions that, confusingly, are called "hydrogen bonding" attractions (even though NO COVALENT BONDS EXIST BETWEEN ANY TWO DIFFERENT MOLECULES!) are H2O, NH3, and HF. Sorry, we just have to live with the name "hydrogen bonding" and make sure that we NEVER confuse it with a covalent bond WITHIN a molecule between H and another atom. In fact, any covalent bond between H and any other atom is about 500 times stronger than a "hydrogen bonding" attraction between separate molecules.
Chem 8/9- I put up some practice test questions with answers on Blackboard. THIS UNIT requires MORE practice than ANY other unit in chemistry. You NEED to do as many problems as possible in order to be prepared for the exam on Wednesday.
we repeated that molecules that have a lone pair or pairs of electrons CAN FORM a coordinate covalent bond (with H+, for example) BUT any POLYATOMIC ION, like NH4+ or H3O+ already HAS a coordinate covalent bond!
We discussed how metal atoms bond to each other, which is called, naturally, metallic bonding.
Metal atoms have too few valence electrons to form an octet between two atoms so they mutually share their valence electrons in a lattice of positive metal nuclei. Each valence electron is only weakly attracted to any one nucleus (low Zeff) so the valence electrons are relatively free to flow throughout the lattice, which is why metals are good electrical conductors. All of the mutual attractions between all neighboring valence electrons and their neighboring positive nuclei make metallic bonds very strong.
We looked at the THREE different types of INTERmolecular attractions. BY DEFINITION, INTER means BETWEEN and molecular means molecules, so intermolecular attractions are NOT BONDS!!! They are merely the attractions BETWEEN the PARTIALLY positively charged side of one molecule and the PARTIALLY negatively charged side of a NEARBY separate molecule. There is NO sharing of electrons, there are NO fully charged IONS. End of story.
So,
(1) NONPOLAR MOLECULES can only form the weakest of intermolecular attractions (London Dispersion/Van der Waals/induced dipole) because any dipoles that form are random and short-lived.
(2) POLAR MOLECULES form stronger intermolecular attractions between their permanent dipoles ( attraction of the partial positive side of one molecule to the partial negative side of another molecule); these attractions are called DIPOLE-DIPOLE attractions.
(3) EXTREMELY POLAR MOLECULES:
Molecules that have H covalently bonded to F, O, or N are extremely polar. There is such unequal sharing of electrons between the (low electronegativity:2.1) H and the highly electronegative F,O, or N (4.0, 3.5, and 3.0) that the molecule has most of its electrons on ONE SIDE of the molecule (by F, O, or N) most of the time. Therefore, an EXTREME partial negative charge is permanently near the F, O, or N part of the molecule and an EXTREME partial positive charge is near the H part(s) of the molecule. So separate molecules will have EXTREME DIPOLE-DIPOLE attractions causing the molecules to stay near each other even at high avg KE (near room temperature). Classic examples of molecules that have these EXTREME DIPOLE-DIPOLE attractions that, confusingly, are called "hydrogen bonding" attractions (even though NO COVALENT BONDS EXIST BETWEEN ANY TWO DIFFERENT MOLECULES!) are H2O, NH3, and HF. Sorry, we just have to live with the name "hydrogen bonding" and make sure that we NEVER confuse it with a covalent bond WITHIN a molecule between H and another atom. In fact, any covalent bond between H and any other atom is about 500 times stronger than a "hydrogen bonding" attraction between separate molecules.
# posted by C @ 11:58 AM 
