Carbon Chemistry

What’s so special about Carbon? Carbon is the fourth most abundant element in the universe, and is absolutely essential to life on earth. Every organism on Earth needs carbon either for structure, energy, or, as in the case of humans, for both. Discounting water, YOU are about half carbon. Additionally, carbon is found in forms as diverse as the gas carbon dioxide (CO2), and in solids like limestone (CaCO3), wood, plastic, diamonds, and graphite.

Carbon – The Element of Life Due to its unique structure, carbon forms many different organic and inorganic compounds. Carbon’s unique atomic structure allows it to covalently bond with up to four other atoms.. why? Carbon is the lightest element on the periodic table that has four valence electrons. If each valence electron is used to form a bond with another atom, carbon reaches 8 electrons in its valence shell and is stable. Elements with either less or more than 4 valence electrons can only form a maximum of 3 covalent bonds, this is why 4 is a magic number and why carbon is special. Drawing of carbon and it’s bonding ability: C

Organic Compounds Organic compounds are those compounds found in any organism that is living or was once living. Examples are sucrose (C12H22O11) and methane (CH4). Compounds from never living substances are referred to as “inorganic.” Examples are limestone (CaCO3) and carbon dioxide (CO2). We like to define compounds chemically, however, so organic compounds are instead given the following definition: Organic Compound – any compound that contains the elements carbon and hydrogen.

Carbon Compounds Carbon can be bonded covalently to up to four other atoms, but what a carbon is bonded to can be very simple or very complex. Hydrocarbons – when a carbon atom is bonded only to hydrogen atoms. Gasoline and fossil fuels are examples of hydrocarbons Carbon chains – when many carbons are bonded together to make long chains or rings. Often consist of many hydrocarbons bonded together called polymers

Properties of Hydrocarbons Hydrocarbons are the simplest organic compounds, made up of only two elements -- they have low melting and boiling points -- hydrocarbons are flammable and tend to burn in combustion reactions -- hydrocarbons mix poorly with water (they are nonpolar) -- hydrocarbons are used for many of our fuels such as heating oil, diesel fuel, gasoline, coal and methane.

What are “polymers”? A polymer is a large molecule that is created when monomers are joined together. A monomer is a single unit that is used to build a polymer. Polymers may be naturally occurring or man-made (synthetic).

Polymerization

used for: flexible bottles, ice trays, plastic bags Some examples of synthetic polymer structures: Polyethylene (PE) used for: flexible bottles, ice trays, plastic bags

Polyvinyl Chloride (PVC) used for: pipes, bottles, CD’s, computer housings

used for: rope, luggage, carpet, film, polar fleece Polypropylene (PP) used for: rope, luggage, carpet, film, polar fleece propylene

used for: toys, packaging, egg cartons, flotation devices, hot cups Polystyrene (PS) used for: toys, packaging, egg cartons, flotation devices, hot cups

Straight Chained Polymer (made up of one type of monomer) Spaghetti-like structure of straight chain polymers. Coils lead to entanglement (stiffness).

A copolymer is made up of more than one type of monomer. Straight Chained Polymer (made up of more than one type of monomer) A copolymer is made up of more than one type of monomer.

Branched Chain Polymer Branching reduces the density and increases the flexibility of a polymer.

Cross Linked Polymers Cross-linking increases stiffness and strength of a polymer.

Vulcanizing Rubber to make it more flexible, tougher and temperature resistant and involves adding Sulfur atoms to create cross-links.

Properties of Polymers Properties are determined by the structure of the molecules and depend on: -type of monomers used -chain length -branching -degree of cross-linking

Branching creates more flexibility; less rigid plastic Low density polyethylene has more branches, so it cannot be packed as closely as in linear, high density polyethylene.

Branching and Cross-links affect strength DIRECTION OF INCREASING STRENGTH

Polymer Structure Branched, Cross-linked or Linear?

Natural and Synthetic Polymers

Some Natural Polymers in Food… Gelatin in gummi worms and gummi bears are made from natural polymers! Bubble gum contains styrene butadiene rubber! Carbohydrates (starches) and proteins are examples of natural polymers! natural polymers

Polymers are everywhere!!! Polymers at the movies…. Nylon carpet, polyester and acrylic seats, polyester curtains, nylon screen, polyester film strip, waxy polyethylene popcorn tub, starch in popcorn, polystyrene cups, plastic M&M bag, protein in hotdogs, gelatin in gummy bears, paraffin in Junior Mints, sticky stuff on the floor made of soda, butter, Skittles, Milk Duds and more…

Where does the material to make polymers come from? Materials produced from the “cracking” of petroleum are the starting points for the production of many synthetic compounds like polymers. Cracking is the process whereby complex organic molecules such as heavy hydrocarbons are broken down into simpler molecules.

Carbon technology: Risks and Benefits?!? -Plastics are used in many useful products, including medical uses Synthetic fibers have better properties than natural fibers Pharmaceuticals are produced from hydrocarbons Fossil fuels are “easy” sources of energy …. Concerns: -Uses up non-renewable resources -Problems with petroleum acquisition and refining processes -Creates long-lasting waste (6-pack rings, non biodegradable material) -Burning hydrocarbons creates CO2 -….

The Carbon Cycle Elements such as Carbon exist in fixed (limited) amounts on the earth and are located in various chemical pools called reservoirs. The movement of carbon, in its many forms, between the atmosphere, oceans, biosphere, and solid earth is described by the carbon cycle. This cycle is driven by both the Earth’s internal (geothermal) energy, and the external energy from the sun and can be divided into geological, chemical and biological components.

Carbon Cycle Processes The geological component of the carbon cycle is where it interacts with the rock cycle in the processes of weathering and dissolution, formation of minerals, burial and subduction, and volcanism. Biology plays an important role in the movement of carbon between land, ocean, and atmosphere through the processes of photosynthesis and respiration. Chemical changes are involved in combustion and decomposition reactions. The geological carbon cycle operates on a time scale of millions of years, whereas the biological and chemical carbon cycle operates on a time scale of days to thousands of years.

The global carbon cycle Sources and sinks of carbon will add or remove carbon from the active part of the cycle. Carbon sinks include long-lived trees, limestone (formed from shells of small sea creatures that settle to the ocean bottoms, plastic, and the burial of organic matter (form fossil fuels). Carbon sources include the burning of fossil fuels and other organic matter, the weathering of limestone rocks (CO2 released), volcanic activity, forest destruction, and the respiration of living organisms. Reservoirs (in black) are gigatons (1Gt = 1x109 Tons) of carbon, and fluxes (in purple) are Gt carbon per year.

Natural and Unnatural CO2 Patterns Relative concentration of CO2 The “Keeling curve” is a long-term record of atmospheric CO2 concentration measured at the Mauna Loa Observatory. Although the annual oscillations represent natural seasonal variations, the long-term increase means that concentrations are higher than they have been in 400,000 years.

Human alteration of the Carbon Cycle Human activities are significantly altering the natural carbon cycle. Since the beginning of the industrial revolution about 150 years ago, human activities such as the burning of fossil fuels and deforestation have increased, and both have contributed to a long-term rise in atmospheric CO2. Burning oil and coal releases carbon into the atmosphere far more rapidly than it is being removed, and this imbalance causes atmospheric carbon dioxide concentrations to increase. In addition, by clearing forests, we reduce the ability of photosynthesis to remove CO2 from the atmosphere, also resulting in a net increase.

Because of these human activities, atmospheric carbon dioxide concentrations are higher today than they have been over the last half-million years or longer!

Review of the Greenhouse Effect The Sun’s short-wave energy passes through the car’s windshield. This energy is absorbed inside the car. The long-wave heat produced cannot pass back through the windshield and is trapped, causing the inside of the car to warm up.

How Global Warming Works Background CO2 Natural Energy Balance Increased CO2 Carbon Dioxide (CO2) Fossil fuels (coal, oil, natural gas)

What is the Difference? GLOBAL WARMING is the increase of the Earth’s average surface temperature due to a build-up of greenhouse gases in the atmosphere. CLIMATE CHANGE is a broader term that refers to long-term changes in climate, including average temperature, precipitation and storm frequency.

Effects of Global Warming Rising Sea Level and Flooding Increased Temperature and Drought Habitat Damage and Species Affected Changes in Water Supply

How do we know that global warming is ALREADY happening? 1914 2004 Portage Glacier, Alaska Photos: NOAA Photo Collection and Gary Braasch – WorldViewOfGlobalWarming.org

Global Atmospheric Concentration of CO2

1000 Years of CO2 and Global Warming Temperature (Northern Hemisphere) CO2 Concentrations Degree Celsius Increase Parts Per Million 1000 1200 1400 1600 1800 2000 1000 1200 1400 1600 1800 2000 Year Year

Billions of Metric Tons Carbon Goal: Reductions in CO2 Per Year 2007

Billions of Metric Tons Carbon Our Goal Billions of Metric Tons Carbon Produce electricity efficiently Use electricity efficiently Vehicle efficiency Solar and Wind Power Biofuels Carbon capture and storage Gigaton Carbon Reductions in CO2 Per Year 2007

Simple Things YOU Can Do Use alternative energy sources and more fuel-efficient cars. Turn off your computer or the TV when you’re not using it. Take shorter showers. Heating water uses energy. Keep rooms cool by closing the blinds, shades, or curtains. Turn off the lights when you leave a room and use compact fluorescent bulbs.

Simple Things To Do…. Dress lightly when it’s hot instead of turning up the air conditioning. Or use a fan. Dress warmly when it’s cold instead of turning up the heat. Keep the air filters on your AC and furnace clean. Walk short distances instead of asking for a ride in the car. Plant a tree. Recycle.

CAPT LAB: Synthetic Polymers Polymers are large molecules consisting of chains of small molecules called monomers joined together in a repeating pattern. In the early 1900s, scientists began to understand the makeup of natural polymers and how to make synthetic polymers with properties that complement, or improve on, those of natural materials. One simple synthetic polymer chemists developed is polyethylene. They developed it by repeating units of the monomer ethylene (H2C=CH2). Polyethylene is a very large, zigzag-shaped molecule. One small part of a polyethylene chain is shown below.

CAPT LAB: Synthetic Polymers Chemists and engineers have learned to process and modify molecules of polyethylene in different ways to manufacture common household products with a variety of characteristics. Polyethylene is used to make plastic trash bags, dry cleaning bags, milk jugs and soda bottles. In industry, materials made from polyethylene are tested for what are called “stress-strain behaviors.” stress-strain behaviors include: Tensile strength - the amount of pulling force placed on a material before it breaks Abrasion resistance - toughness of a material against scraping, scuffing or scarring Puncture resistance –ability of a material to keep moving objects from perforating the surface.

CAPT LAB: Synthetic Polymers Your task You and your lab partners will design an experiment that investigates one stress-strain behaviors of various plastic products made of the synthetic polymer polyethylene. You have been provided with an assortment of plastic products to test. The stress-strain behaviors you will investigate are tensile strength or puncture resistance. Remember the importance of only testing ONE variable at a time, keeping all others constant as much as possible.

CAPT LAB: Synthetic Polymers Tensile strength The tensile strength of a material measures how much pulling stress the material will endure before failing. This is very important in applications that depend on a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length. Puncture resistance The puncture resistance of a material measures how much force is required for a moving object to break through a material. This is also very important for certain applications such as trash bags –a greater puncture resistance will result in less trash poking through and spilling out on the ground! Puncture resistance also generally increases with greater chain length.

CAPT LAB: Synthetic Polymers Designing Your Experiment In your own words, state the problem you are going to investigate. Write a hypothesis using an “If… then… because..” statement that describes what you expect to find and why. Include a clear identification of the independent and dependent variables that will be studied. Your experimental design should match the statement of the problem and should be clearly described so someone else could replicate the experiment. Use a diagram if necessary to help explain your design.

CAPT LAB: Synthetic Polymers Things to consider in your design: 1. How will you measure the amount of stretching the plastic can endure? What will you consider the starting point? What will be the ending point? 2. How can you keep the force of a moving object constant? Is there a natural force you can use that is ALWAYS the same? Remember the importance of only testing ONE variable at a time, keeping all others constant as much as possible. Also remember the importance of making valid conclusions from your data… how many trials will you do?

Create Your Own Carbon Cycle Diagram Use different colors for reservoirs and fluxes, and include pictures to represent storage or processes. Include a key to explain your diagram.

Create Your Own Carbon Cycle Diagram *only shows atmosphere fluxes gases (CO2, CH4) (sink) (source) death and decay released photosynthesis respiration dissolves (source) plants (sink) combustion dissolved in ocean animals fossil fuels sediment deposits Blue arrows (fluxes) represent the active carbon cycle. Green boxes are reservoirs where carbon is stored. Each flux can be thought of as either a source (adding carbon to the active cycle) or a sink (removing carbon from the cycle).