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

B10.81

Boron

5

5 protons6 neutrons

Bohr model of BoronPeriodic table ccasa by Armtuk http://commons.wikimedia.org/wiki/Image:Periodic_Table_Armtuk3.svg; 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

B10.81

Boron

5

5 protons6 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 protons11 electrons

11 protons10 electrons

17 protons17 electrons

17 protons18 electrons

Chlorine atom (Cl)Sodium atom (Na)

Chlorine atom (Cl-)Sodium atom (Na+)

The periodic table

Periodic table ccasa by Armtuk http://commons.wikimedia.org/wiki/Image:Periodic_Table_Armtuk3.svg; 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 Basic

Highly Acidic

Few protons (H+)

pH Scale ccasa by Slower http://commons.wikimedia.org/wiki/Image:PH_scale.png

Acid Base

HCl

ClH

NaOH

OHNa

(hydrochloric acid) (sodium hydroxide / lye)

pH Scale ccasa by Slower http://commons.wikimedia.org/wiki/Image:PH_scale.png

pH’s of common

items

Lots of protons (H+)

Highly Basic

Highly Acidic

Few protons (H+)

Buffers

• Chemicals that maintain a constant pH in a solution, even when acid or base is added

• Example: Bicarbonate (NaHCO3)

– In solution dissociates into Na+ and (HCO3)-

2333222 COHHCOHCOHOHCO

3HCO

332 HCOHCOH 233 COHHCO

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 H2O = 1g

Meniscus diagram gnu FDL by Jleedev: http://en.wikipedia.org/wiki/Image:Reading_the_meniscus.png

Read the volume at the bottom of the meniscus

The periodic table

Periodic table ccasa by Armtuk http://commons.wikimedia.org/wiki/Image:Periodic_Table_Armtuk3.svg; 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:– http://www.iupac.org/reports/periodic_table/

License information

• This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

• The slides in this presentation were originally created by Marc C. Perkins (http://faculty.orangecoastcollege.edu/mperkins).

• You are free to use, modify, and distribute these slides according to the terms of the Creative Commons license (e.g., you must attribute the slides, no commercial uses are allowed, and future distributions must be licensed under a similar license).

• Attribution should be given to Marc C. Perkins (and any later editors), including a link back to Marc’s current website. This applies both while distributing the slides and during use of the slides; attribution during use can be satisfied by, for instance, placing small text on at least one of the slides that has been shown (see below for an example).

Slides in this presentation based on those created by Marc C. Perkins. http://faculty.orangecoastcollege.edu/mperkins

History

• August 2007: Marc Perkins released first version. http://faculty.orangecoastcollege.edu/mperkins

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