Lab 1 – Introduction to biological sciences No quiz or worksheet due today

Outline of today’s lab Atoms –What are they made of? –What makes different atoms different? –How are ions and anions formed? pH –What is it? –What is the pH of various solutions? –What are buffers? Using the metric system –Practicing measurements / unit conversions.

Atoms! Composed of protons, neutrons, and electrons –Protons = +1 charge –Electrons = -1 charge –Neutrons = neutral Bohr Model is the classic model –Protons and neutrons in the nucleus –Electrons in shells around the nucleus B Boron 5 5 protons 6 neutrons Bohr model of Boron Periodic table ccasa by Armtuk Boron art by Marc Perkins

How do we figure out what’s in each atom? Protons –# protons = Atomic number Neutrons –# neutrons = Atomic mass - # protons Unless it’s an isotope Electrons –# electrons = # protons Unless it’s an ion B Boron 5 5 protons 6 neutrons Atomic number Atomic mass

Ions: gaining or losing electrons Salt –NaCl –Sodium Chloride Na and Cl become ions –Na loses an electron –Cl gains an electron Written as –Na + –Cl - 11 protons 11 electrons 11 protons 10 electrons 17 protons 17 electrons 17 protons 18 electrons Chlorine atom (Cl) Sodium atom (Na) Chlorine atom (Cl - ) Sodium atom (Na + )

The periodic table Periodic table ccasa by Armtuk Boron art by Marc Perkins

Outline of today’s lab Atoms –What are they made of? –What makes different atoms different? –How are ions and anions formed? pH –What is it? –What is the pH of various solutions? –What are buffers? Using the metric system –Practicing measurements / unit conversions

Acidity Completely dependent on the concentration of protons (H + ) in solution –The more protons (H + ), the more acidic –The more things that absorb protons (e.g., OH - ), the more basic Lots of protons (H + )Highly BasicHighly AcidicFew protons (H + ) pH Scale ccasa by Slower

Acid Base (hydrochloric acid) (sodium hydroxide / lye)

pH Scale ccasa by Slower pH’s of common items Lots of protons (H + )Highly BasicHighly AcidicFew protons (H + )

Buffers Chemicals that maintain a constant pH in a solution, even when acid or base is added Example: Bicarbonate (NaHCO 3 ) –In solution dissociates into Na + and (HCO 3 ) - If we add an acid (H + ) If we add a base (OH - ) Bicarbonate absorbs the proton!Bicarbonate produces a proton! (that will react with OH- to form H2O)

Outline of today’s lab Atoms –What are they made of? –What makes different atoms different? –How are ions and anions formed? pH –What is it? –What is the pH of various solutions? –What are buffers? Using the metric system –Practicing measurements / unit conversions

Measuring volume Use the pipettes, graduated cylinders, or the scale –1 ml H 2 O = 1g Meniscus diagram gnu FDL by Jleedev: Read the volume at the bottom of the meniscus

The periodic table Periodic table ccasa by Armtuk Boron art by Marc Perkins

Before you leave Clean up your work area –Wash glassware and store upside down Show me your lab report so I can stamp it –Need to have all data fields filled in –Complete at home and then turn in at the beginning of next lab Remember that we’ll have a quiz at the beginning of the next class –6-7 questions on today’s lab –3-4 questions on the lab we’ll do next week

Notes for the instructor: If you need a screen-displayable periodic table that shows atomic masses, try this one by the IUPAC: –

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