Thursday, March 13, 2008
Thurs-Day 2
Bio- HW: outline of Section 38.2 is due tomorrow, Friday. (Section 38.3 will be due next Tuesday).
Today, we continued to show how and why MEIOSIS is the source of genetic variety among sex cells/gametes. Meiosis also causes the gamete cells to have exactly HALF the total number (23, for humans) of chromosomes inside any other type of cell (46, for humans) in the body. However, each gamete still has one of EACH different TYPE of chromosome so that all traits are still coded for by each gamete. This halving of the number of chromosomes is necessary because the sex cell has one and only ONE job: to unit with the opposite sex cell causing the fertilized egg's nucleus to have 23 PAIRS of chromosome or 46 total chromosomes, which are necessary to form a human.
Chem 7/8- we continued with various naming, writing, balancing, and stoichiometry problems.
Some common errors were discussed:
when converting from grams to moles for ANY substance, you must divide by the FORMULA MASS (i.e. the MOLAR MASS, the mass of ONE MOLE, NEVER any other number of moles) of THAT SUBSTANCE. Never use the coefficient in front of the substance in calculating formula mass; those coefficients change for a given substance depending on the chemical reaction; you must ONLY used the subscripts in the substance's formula in calculating the molar mass of a substance e.g. O2 has a molar mass of 32.0 g but O3 has a molar mass of 48.0 g.
When naming salts, go to Table E for ANY "ate" or "ite" salts; for "ide", salts, just use the actual nonmetal from the Periodic Table...e.g. Calcium Fluoride is CaF2 or Calcium Sulfide is CaS.
In all calculations, ALWAYS write units AND the substance referred to by those units!
In writing salt formulas, ALWAYS look up and BALANCE the ionic charges first so that you can tell the ratio of cations to anions in each formula unit; if you have more than ONE of the polyatomic ion in each formula unit, it MUST be in parentheses. If you have ONLY one of the polyatomic ion in each formula unit, you CANNOT use parentheses.
We discussed and handed in some recent labs: "percent hydrate in a salt", "esterification", and classification of organic compounds (hand in if you have not done so already).
We will discuss our sodium hydrogen carbonate and hydrochloric acid reaction on Monday.
Chem 9- we continued with various naming, writing, balancing, and stoichiometry problems.
Some common errors were discussed:
when converting from grams to moles for ANY substance, you must divide by the FORMULA MASS (i.e. the MOLAR MASS, the mass of ONE MOLE, NEVER any other number of moles) of THAT SUBSTANCE. Never use the coefficient in front of the substance in calculating formula mass; those coefficients change for a given substance depending on the chemical reaction; you must ONLY used the subscripts in the substance's formula in calculating the molar mass of a substance e.g. O2 has a molar mass of 32.0 g but O3 has a molar mass of 48.0 g.
When naming salts, go to Table E for ANY "ate" or "ite" salts; for "ide", salts, just use the actual nonmetal from the Periodic Table...e.g. Calcium Fluoride is CaF2 or Calcium Sulfide is CaS.
In all calculations, ALWAYS write units AND the substance referred to by those units!
In writing salt formulas, ALWAYS look up and BALANCE the ionic charges first so that you can tell the ratio of cations to anions in each formula unit; if you have more than ONE of the polyatomic ion in each formula unit, it MUST be in parentheses. If you have ONLY one of the polyatomic ion in each formula unit, you CANNOT use parentheses.
Today, we continued to show how and why MEIOSIS is the source of genetic variety among sex cells/gametes. Meiosis also causes the gamete cells to have exactly HALF the total number (23, for humans) of chromosomes inside any other type of cell (46, for humans) in the body. However, each gamete still has one of EACH different TYPE of chromosome so that all traits are still coded for by each gamete. This halving of the number of chromosomes is necessary because the sex cell has one and only ONE job: to unit with the opposite sex cell causing the fertilized egg's nucleus to have 23 PAIRS of chromosome or 46 total chromosomes, which are necessary to form a human.
Chem 7/8- we continued with various naming, writing, balancing, and stoichiometry problems.
Some common errors were discussed:
when converting from grams to moles for ANY substance, you must divide by the FORMULA MASS (i.e. the MOLAR MASS, the mass of ONE MOLE, NEVER any other number of moles) of THAT SUBSTANCE. Never use the coefficient in front of the substance in calculating formula mass; those coefficients change for a given substance depending on the chemical reaction; you must ONLY used the subscripts in the substance's formula in calculating the molar mass of a substance e.g. O2 has a molar mass of 32.0 g but O3 has a molar mass of 48.0 g.
When naming salts, go to Table E for ANY "ate" or "ite" salts; for "ide", salts, just use the actual nonmetal from the Periodic Table...e.g. Calcium Fluoride is CaF2 or Calcium Sulfide is CaS.
In all calculations, ALWAYS write units AND the substance referred to by those units!
In writing salt formulas, ALWAYS look up and BALANCE the ionic charges first so that you can tell the ratio of cations to anions in each formula unit; if you have more than ONE of the polyatomic ion in each formula unit, it MUST be in parentheses. If you have ONLY one of the polyatomic ion in each formula unit, you CANNOT use parentheses.
We discussed and handed in some recent labs: "percent hydrate in a salt", "esterification", and classification of organic compounds (hand in if you have not done so already).
We will discuss our sodium hydrogen carbonate and hydrochloric acid reaction on Monday.
Chem 9- we continued with various naming, writing, balancing, and stoichiometry problems.
Some common errors were discussed:
when converting from grams to moles for ANY substance, you must divide by the FORMULA MASS (i.e. the MOLAR MASS, the mass of ONE MOLE, NEVER any other number of moles) of THAT SUBSTANCE. Never use the coefficient in front of the substance in calculating formula mass; those coefficients change for a given substance depending on the chemical reaction; you must ONLY used the subscripts in the substance's formula in calculating the molar mass of a substance e.g. O2 has a molar mass of 32.0 g but O3 has a molar mass of 48.0 g.
When naming salts, go to Table E for ANY "ate" or "ite" salts; for "ide", salts, just use the actual nonmetal from the Periodic Table...e.g. Calcium Fluoride is CaF2 or Calcium Sulfide is CaS.
In all calculations, ALWAYS write units AND the substance referred to by those units!
In writing salt formulas, ALWAYS look up and BALANCE the ionic charges first so that you can tell the ratio of cations to anions in each formula unit; if you have more than ONE of the polyatomic ion in each formula unit, it MUST be in parentheses. If you have ONLY one of the polyatomic ion in each formula unit, you CANNOT use parentheses.
# posted by C @ 1:43 PM 
