Question

Performance Models are often used to visualize the three-dimensional shape of molecules. Using gumdrops as atoms and toothpicks to bond them together, construct models of different hydrocarbons. Use large gumdrops for carbon and smaller gumdrops for hydrogen.

Short answer

Gather materials, then construct methane, ethane, propane, and butane models by appropriately connecting gumdrops with toothpicks.

Step-by-step solution

Gather Materials

Collect large gumdrops to represent carbon atoms and smaller gumdrops to represent hydrogen atoms. Also, gather toothpicks which will be used to form bonds between the atoms.

Construct Methane (CH₄) Model

Start with one large gumdrop (carbon) and connect it to four small gumdrops (hydrogen) using toothpicks to form a tetrahedral shape.

Construct Ethane (C₂H₆) Model

Use two large gumdrops (carbons) and connect them with a toothpick. Then, attach three small gumdrops (hydrogens) to each of the carbon gumdrops using toothpicks.

Construct Propane (C₃H₈) Model

Use three large gumdrops (carbons) and connect them in a straight line with toothpicks. Then, attach two small gumdrops (hydrogens) to each of the end carbon atoms and three small gumdrops (hydrogens) to the middle carbon atom using toothpicks.

Construct Butane (C₄H₁₀) Model

Use four large gumdrops (carbons) and connect them in a straight line with toothpicks. Attach two small gumdrops (hydrogens) to each of the end carbon atoms and two small gumdrops (hydrogens) to each of the two middle carbon atoms using toothpicks.

Key concepts

Hydrocarbons

Hydrocarbons are organic compounds composed solely of hydrogen and carbon atoms. They are the simplest organic molecules and form the basis for many other compounds.

There are different types of hydrocarbons, but in this exercise, we focus on alkanes. Alkanes are saturated hydrocarbons, meaning they only have single bonds between carbon atoms. Here are some of the alkanes we constructed in the exercise:

• **Methane (CH₄)**: Simplest alkane with one carbon atom bonded to four hydrogen atoms in a tetrahedral shape.
• **Ethane (C₂H₆)**: Consists of two carbon atoms bonded together, with each carbon bonded to three hydrogen atoms.
• **Propane (C₃H₈)**: A chain of three carbon atoms where each end carbon is bonded to two hydrogen atoms, and the middle carbon is bonded to two hydrogen atoms.
• **Butane (C₄H₁₀)**: Four carbon atoms in a line with each end carbon bonded to three hydrogen atoms and the middle two carbons bonded to two hydrogen atoms.

Understanding the structure of these hydrocarbons is crucial for grasping more complex organic chemistry concepts.

Three-Dimensional Molecular Shapes

Visualizing molecules in three dimensions is key to understanding their chemical properties and behavior.

When constructing models, we often use physical models like gumdrops and toothpicks or computer simulations to see how atoms arrange themselves in three-dimensional space.

For example, methane (CH₄) forms a *tetrahedral shape*, where the hydrogen atoms are evenly spaced around the central carbon atom. This arrangement minimizes the repulsion between the electron pairs around the carbon, resulting in a stable structure.

Ethane (C₂H₆) also adopts a three-dimensional shape, with the two carbon atoms connected by a single bond and each carbon adopting a tetrahedral geometry with its hydrogen atoms.

As we build larger hydrocarbons like propane (C₃H₈) and butane (C₄H₁₀), the three-dimensional arrangement of their atoms becomes more complex. Understanding these shapes helps us predict how they will interact with other molecules and what kinds of reactions they may undergo.

Chemical Bonding

Chemical bonding is the force that holds atoms together in molecules. In hydrocarbons, the primary type of bond is the *covalent bond*, where atoms share pairs of electrons.

In our models:

• **Single Bonds**: Each toothpick represents a single covalent bond where two atoms share one pair of electrons. For example, in methane, each carbon-hydrogen bond is a single bond.
• **Bond Strength and Length**: Single bonds are relatively long and weak compared to double and triple bonds (though we did not use those in our simple alkane models).

Understanding these basic bonds helps in predicting the physical and chemical properties of the molecules.

The shape and stability of molecules like the ones we built depend on these bonding interactions. For instance, the tetrahedral geometry of methane arises because the four pairs of bonding electrons around carbon repel each other, arranging themselves as far apart as possible.

As we move to more complex molecules like propane and butane, the additional single bonds between carbon atoms add to the overall stability and flexibility of the molecule.

These basic concepts of chemical bonding are fundamental for delving deeper into topics like reactivity, synthesis, and more advanced structural chemistry.