L3: Molecular polarity

Not all _______ bonds are created equal! Some have an ionic character if one atom attracts the bonding electrons more strongly than the other.

• ionic

• covalent

• metallic

• non-polar

Answer explanation

Explanation: Covalent bonds can exhibit varying degrees of ionic character depending on the electronegativity difference between the atoms involved. This means not all covalent bonds are identical, unlike purely ionic or metallic bonds.

1. Fun Fact: This creates polar covalent bonds, which are common in molecules like water and ammonia.

Electronegativity is like an atom's "pull" on electrons. Atoms on the _______ side of the periodic table tend to pull electrons more strongly than those on the left.

• left

• right

• up

• down

Answer explanation

Explanation: Electronegativity measures an atom's ability to attract electrons. Atoms on the right side of the periodic table, like halogens, have higher electronegativity and thus a stronger pull on electrons compared to those on the left.

1. Fun Fact: This is why oxygen in water attracts electrons more than hydrogen, giving water its unique properties!

Molecules can have net dipoles if one side is more positive or negative, making them _____. This affects how they interact with other molecules.

• polar

• non-polar

• inert

• benign

Answer explanation

Explanation: Molecules with net dipoles are polar, meaning one side is more positive or negative. This polarity influences their interactions with other molecules, making it crucial in understanding chemical behavior.

3. Fun Fact: The net dipole in water is why it can dissolve so many substances, making it the "universal solvent."

Molecules with similar electronegativity between atoms are usually ______ because they share electrons evenly, resulting in no net dipole.

• solid

• gas

• polar

• non-polar

Answer explanation

Explanation: Molecules with similar electronegativity share electrons evenly, leading to a balanced distribution of charge. This results in no net dipole, making them nonpolar. Thus, the statement is correct.

Real-Life Fun Fact: Because of its nonpolar nature, carbon dioxide in its solid form (dry ice) doesn’t dissolve in polar liquids like water in the same way as polar substances do. Instead, it sublimates directly into gas, making it ideal for creating fog effects at parties, concerts, and in theater!

______ substances tend to dissolve in polar solvents, while ______ substances dissolve in nonpolar solvents.

• Polar, polar

• Polar, non-polar

• Non-polar, polar

• Non-polar, non-polar

Answer explanation

Explanation: Polar substances dissolve in polar solvents due to similar intermolecular forces, while nonpolar substances dissolve in nonpolar solvents for the same reason. This principle is key in understanding solubility.

5. Fun Fact: This is why oil and vinegar don’t mix, but adding an emulsifier, like mustard, can help bring them together in salad dressing!

___________ interactions are weaker than _________ but still crucial-they determine whether a substance is a gas, liquid, or solid.

• Inter-molecular forces, Intra-molecular forces

• Intra-molecular forces, Inter-molecular forces

• Hydrogen bonding, Van der Waals

• Dipole-dipole, Van der Waals

Answer explanation

Explanation: Intermolecular forces interactions, though weaker than intramolecular forces, are essential in determining the physical state of substances (gas, liquid, solid) due to their influence on molecular arrangements and behaviors.

7. Fun Fact: These forces are the reason why ice floats. When water freezes, hydrogen bonds create an open, hexagonal structure that makes ice less dense than liquid water. If ice sank, our oceans and lakes would freeze from the bottom up, making life in water impossible!

   In essence, intermolecular forces are the "glue" that holds water, proteins, DNA, and even cell membranes together. Without them, the organized, stable structures essential for life simply couldn’t exist.

_______ molecules attract each other through dipole-dipole interactions where opposite charges align, like in acetone.

• Non-binding

• Non-charged

• Non-polar

• Polar

Answer explanation

Explanation: Polar molecules, like acetone, have regions of positive and negative charge. They attract each other through dipole-dipole interactions, where the positive end of one molecule aligns with the negative end of another, enhancing stability.

• Fun Fact: Perfumes are made of polar molecules that have dipole-dipole interactions. When applied to your skin, these molecules interact with the natural oils on your skin, which helps them stick and release gradually over time. This is why perfume lasts longer on skin than if you simply spray it in the air!

Even nonpolar molecules, like oxygen (O₂) and nitrogen (N₂), experience weak forces called ________.

• ionic

• hydrogen bonding

• covalent

• Van der Waals

Answer explanation

Explanation: London dispersion forces are weak intermolecular forces that occur in all molecules, including nonpolar ones like O₂ and N₂, due to temporary fluctuations in electron distribution.

Fun Fact: Butter is made up of nonpolar molecules, which stick together through London dispersion forces. These forces are weak compared to other types of bonds, so butter stays solid at cooler temperatures but melts quickly when warmed, making it ideal for spreading on toast!

Hydrogen bonds are a special type of strong dipole-dipole attraction, only occurring when hydrogen is bonded to a highly electronegative atom like _______.

• Boron

• Silicon

• Aluminium

• Fluorine

Answer explanation

Explanation: Hydrogen bonds are indeed strong dipole-dipole attractions that occur specifically when hydrogen is bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine, making this statement accurate.

Fun Fact: Many drugs contain fluorine because fluorine-hydrogen bonds can create very strong interactions with biological molecules. These bonds improve the drug’s ability to bind precisely to its target, increasing its effectiveness. For example, the anti-anxiety medication Prozac contains fluorine to improve its stability and performance in the body.

Miscibility refers to the ability of two liquids to mix together to form a single phase. If they don't mix, they're called _______.

• Miscible

• Immiscible

• gas

• liquid

Answer explanation

Explanation: Miscibility is the ability of two liquids to mix and form a single phase. If they do not mix, they are termed immiscible. Therefore, the statement correctly defines miscibility and immiscibility.

Fun fact: Many salad dressings use an emulsifier, like mustard or egg yolk, which has both polar and nonpolar ends. The polar end interacts with the vinegar, and the nonpolar end interacts with the oil, allowing them to stay blended together. This is also how mayonnaise holds its creamy texture!