Ocean Chemistry: Solutions LA Charter School Science Partnership 15 October 2011 Nick Klein.

transcript

Ocean Chemistry: Solutions

LA Charter School Science Partnership

15 October 2011

Nick Klein

Today’s Talk

• Intro & Biography

• Part 1: Chemistry review, phases of matter

• Part 2: Chemical solutions

• Part 3: Solutions in the ocean context

About Me

• Third year PhD student in Earth Sciences

• BA Biology and Chemistry from Augustana College, SD

• I study global impacts of marine trace chemistry

• Thesis research: production of marine halocarbons

Field sampling on Lake Tahoe

Today’s Talk cont’d

• I’ve split this talk into three (roughly) even parts. We will take a brief (2-3min) break between sections. Please feel free to take notes, handle the props on the table at the front of the room, think of questions for after the talk, etc.

Sergio Sañudo-Wilhelmy, my PhD mentor

Part 1: Basic chemistry review

• What is the basic unit of chemistry?– An atom

• How do we define an atom?– Smallest unit of a chemical element that still

has all the unique characteristics of that element

– Indivisible by any chemical means

• Atoms are composed of a nucleus and orbiting electrons

• Nucleus contains protons and neutrons

• Electrons are negatively charged, protons positive. Neutrons are not charged (neutral).

• The identity of an atom is based on the number of protons it has. This is called the atomic number

• Carbon has an atomic number of 6 (6 protons)

• Oxygen has an atomic number of 8 (8 protons)

• An electron has almost no mass (weighs almost nothing)

• Protons and neutrons have the same mass, each weighs 1 atomic mass unit (1 amu)

• Atomic mass is weight (in amu) of an atom and is therefore equal to protons + neutrons!

• Carbon has an atomic mass of 12amu6 protons + 6 neutrons = 12

• Oxygen has an atomic mass of 16amu8 protons + 8 neutrons = 16

• Since electrons weigh nearly nothing, almost all of the mass of an atom is in the nucleus!

• Atoms and molecules are mostly empty space!

A single pea(nucleus)

• Atoms are tiny!

• How many molecules of water are in my flask?

• Answer: about 600 billion trillion, or600,000,000,000,000,000,000,000 molecules of water!

• The kinetic molecular theory of matter:

We can describe the behavior of matterbased on what we know about how the individual molecules are moving.

• Three phases of matter: solid, liquid, gas• Solid – slowest movement of molecules,

just vibrating• Liquid—molecules moving enough to be

able to flow over and around each other• Gas—molecules moving very rapidly, fill

the available space

• Three phases of matter: solid, liquid, gas• Solid – slowest movement of molecules,

just vibrating• Liquid—molecules moving enough to be

able to flow over and around each other• Gas—molecules moving very rapidly, fill

the available space

• Solid—fixed shape and volume, molecules cannot move

• Liquid—no fixed shape, but volume stays the same. Molecules can flow.

• Gas—no fixed shape OR volume, molecules spread to fill the available space.

http://www.youtube.com/v/akUuFsH4B1c

Counting molecules- we use a special unit called the “mole” = 6.02 x 1023 molecules or atoms

There are 6.02 x 1023 protons in one gram of protons (or neutrons)

• This allows us to easily convert from amu on the periodic table into molecules of a substance!

Part 2: Solutions

• What is a solution?

• How do we define a chemical solution?

A mixture of two or more substanceswhich are dispersed homogenously on a molecular level.

Part 2: Solutions

• Solvent- the substance that is in greater quantity, does the dissolving, usually a liquid

• Solute- the substance that is dissolve,d usually in a lesser quantity, can be solid, liquid, or gas

• How about your morning coffee (or tea, or soda…)?

Part 2: Solutions

• Why don’t oil and vinegar mix? Why do alcohol and water mix?

• Let’s examine the structure of some of these molecules.

Part 2: Solutions

• The answer is polarity• Some molecules have their electrons

unevenly distributed, giving them a more negative and a more positive end

• Nonpolar molecules have electrons evenly distributed throughout

Part 2: Solutions

• Electronegativity – some elements are “greedy” and want electrons more than others. They don’t like to share.

• Oxygen is greedy!

Part 2: Solutions

• Why don’t oil and vinegar mix? Why do alcohol and water mix?

• Let’s examine the structure of some of these molecules.

Part 2: Solutions-

Part 2: Solutions

LIKE DISSOLVES LIKE!

Part 2: Solutions

• Why do we use soap to wash our dishes?

• How does soap work?

Part 2: Solutions

• Soap molecules are surfactants. They have a charged (polar) head and a relatively uncharged (nonpolar) “tail,” so they can bridge the gap between water and grease! Water is then able to dissolve the grease or oils. This is called an emulsion.

• How might this be important for cleaning up oil spills?

Part 2: Solutions

• Hydrogen bonding is a related concept• Since polar molecules have oppositely

charged ends, they can attract each other and form loose chemical bonds

• This is especially important in water!

Part 2: Solutions

Part 3 – Ocean Context

• Let’s brainstorm!

• Why is the chemistry of the oceans important?

• Cover 75% of Earth’s surface• About 50% of all life on Earth lives in the

oceans (if it weren’t for algae, we wouldn’t have oxygen to breathe, too!)

• They moderate our climate and weather by storing and releasing heat

• The story of ocean chemistry is the story of aqueous solutions (solutions with water as the solvent)

• Water has many unique properties because of the chemistry we have discussed

• How many can we come up with?

• Water exists in three distinct states of matter in typical Earth conditions – water vapor (steam, clouds), liquid water, and ice

• Water is a great solvent (3.5% salt)• Water has a high heat capacity• Solid water (ice) is actually less dense

than liquid water and floats

Before you go…

• Think about this scenario and come up with a description (based on the kinetic molecular theory of matter) of what is happening on a macro (large) scale and on the molecular level:

• An iceberg breaks loose in the Arctic and begins to float south into warmer waters.

Ocean Chemistry: Solutions LA Charter School Science Partnership 15 October 2011 Nick Klein.

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