Carbon and Carbon Compounds

Carbon and carbon compounds Focus questions: 1. Why can carbon form so many different compounds? 2. How are properties of carbon and carbon-based substances related to their molecular structure?

Identify the compound in which a carbon atom has 1,2,3 or 4 covalent bonds

Bonding properties of carbon 1.Carbon is unique among other elements because it can bond in many ways with itself as well as other elements 2.The carbon atom can make 1 to 4 covalent bonds with other atoms

3. The Variety in the number of bonds (1 – 4) allows carbon based molecules to have a wide variety of: Different Sizes and Shapes With different chemical and physical properties Linear/Straight Chain Planar (one flat plane) Tetrahedral Carbon atom can also bond to each other in long straight chains, branched chains and ring-shaped groups. These Structures form the backbone’s to which other atoms attach.

Notice the number of bonds between the different carbon atoms. Q: What does each line between the atoms represent? A: The sharing of a valence electron. Sharing of electrons creates a COVALENT BOND.

Carbon compounds have a wide variety of chemical properties 5. The different chemical properties (reactivity) depend on the different atoms attached to the carbon atom. –Hydrogen is the most popular atom bonded with carbon. It creates a wide variety of fuels called hydrocarbons –Can you guess what fuel this is to the left? »Hint: CH 4 –Answer: Methane Gas

Hydrocarbon Examples 6. Small changes in molecular structure can lead to BIG changes in the properties of the substances. such as, density, mechanical strength, hardness, and melting point Why does each fuel ignite at different temperatures?

Familiar Forms of Carbon GraphiteDiamond

Graphite consists of layers of carbon atoms in a hexagonal arrangement. There are weak bonds between layers, allowing the layers to slide over one another (when you write on paper with a pencil). Graphite is used in pencils, as a dry lubricant, and in the electroplating of substances to enhance properties. Graphite

Diamonds have a structure where each carbon atom is bonded to 4 other carbons in a three-dimensional structure. The structure of the diamond allows the carbon atoms to be densely packed and tightly bound, increasing its hardness. Diamonds are the hardest naturally occurring mineral found in nature. Diamonds are used for drills, cutting wheels, and polishing of many substances, as well as for jewelry. Diamonds are forever?!

Comparison of Diamond and Graphite Diamond Very hard Very high density Doesn’t conduct electricity Very high melting point Graphite Soft and Slippery Lower density than diamond Conducts Electricity Lower melting point than Diamond

So Basically… Both graphite and diamonds are made of carbon. What makes them so different? Answer lies in the way in which carbon atoms form bond with each other. –In diamond, there is a rigid structure of atoms that cannot move. –In graphite, weak forces exist between different layers. It is easy to break into layers.

Many carbon-based molecules are made of many small subunits bonded together. –Monomers are the individual subunits. –Polymers are made of many monomers. Polymers can be thought of as chains. They are built of smaller parts bonded Together (momomers)

Any connection between monomers and polymers? 7. Polymer: a giant molecule that is built from smaller, carbon based molecules (called monomers) bonded together. 8. Monomers :are small carbon based molecules that are linked together to form a larger molecule (polymer).

Carbon-based molecules are the foundation of life. AKA, the “Building Block of Life” Types of Carbon Polymers Synthetic Polymer Natural Polymer Carbon molecules form Polymers

Synthetic Polymers Polymers that are made during chemical reactions in lab and factory are synthetic or man-made. Plastics are synthetic polymers that can be molded or shaped.

Familiar Places?

Natural Polymers Polymer resulting from raw materials found in nature Examples of Natural Polymer –Cellulose (plant only) –Starch (plant only) –DNA/RNA –Proteins –Glucose (plant only) Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure. Polymer (cellulose) Cellulose is a polymer of glucose monomers that has a straight, rigid structure monomer

Physical Properties of polymers Physical properties of polymers are affected by small changes in molecular structure. –Density –Mechanical Strength Flexural Strength (try to flex it) Torsion Strength (try to twist it) Impact Resistance (hard or brittle) Tensile Strength (try to pull it apart)

So Basically… Change in the molecular structure of a polymer will change the density and mechanical strength. Factor 1: Polymers having chains with or without branches Factor 2: Chain length Factor 3: Different atoms bonded to carbon backbone

Polymers having chains with or without branches Density –Polymer with branches will be less dense because the branches will prevent the chains from getting close together. Ex: Plastic Bag Flexibility –Polymer with NO branches (more dense) are less flexible and are harder to pull apart (tensile-strength). Ex: Water Bottle

Chain length With polymers, the molecular chains are usually of different length. The different lengths affect the mechanical strength of the material. The mechanical strength of a polymer depends on its average chain length. Longer chains means higher tensile strength ( harder to pull apart). So shorter chains means…

Atoms bonded to Carbon Backbone(s) Properties of the polymer depend on different atoms bonded to carbon atoms in the monomer. –Example: ethylene (plastic) and poly vinyl chloride (PVC) –Only difference between the two is that one hydrogen atom is substituted by a chlorine atom in the vinyl chloride (monomer). The resulting polymer is polyvinyl chloride (PVC pipes). Think plumbing and irrigation –This substitution of 1 atom increase the impact resistance to survive a really long time in harsh conditions.

KEY POINTS 1. Carbon has the ability to form variety of compound because it can bond with itself as well other elements. Carbon can make from 1 to 4 covalent bonds with another atom. 2. Chemical properties of carbon based compounds depends on the atoms and how they are attached to the carbon. This is known as molecular structure of compound. 3. Carbon bonds can make many different shapes leading to a variety of molecular structures 4. Small changes in molecular structure can lead to big changes in the physical properties of the substances (Density, Mechanical strength, Hardness and Melting Point). 4. Monomers :are small carbon based molecules (that are then linked) Polymer: a chain like compound made up of many repeating smaller carbon based molecules bonded together (monomers).