Question

\(\mathrm{A}(\mathrm{n})\) ______ substance repels water. a. acidic b. basic c. hydrophobic d. polar

Short answer

The correct answer is (c) hydrophobic.

Step-by-step solution

Understanding the Exercise

This exercise asks us to identify a term that describes a substance that repels water. We need to know the meanings of the choices provided: acidic, basic, hydrophobic, and polar.

Define the Terms

- **Acidic substances** are those with a low pH and tend to release hydrogen ions in water. They do not particularly repel water. - **Basic substances** have a high pH and can accept hydrogen ions. Like acids, they interact with water but in a different chemical way. - **Hydrophobic substances** are those that do not mix with water and often repel it, such as oils. - **Polar substances** typically dissolve in water because of their charge distribution that allows them to interact with water molecules.

Identify the Correct Term

The term that means a substance repels water is **hydrophobic**. Hydrophobic substances do not interact with water and often form separate layers when mixed with water. This is because they lack the polar attributes needed to interact with water molecules.

Key concepts

Polar Substances

Polar substances have molecules that possess a positive and negative end. This distribution of electric charge, called a dipole, allows them to interact easily with water, which is a polar solvent. In simple terms, polar substances like to dissolve in water.

Why do polar substances dissolve in water? It's all about attraction. Polar molecules attract water molecules, leading to interactions such as hydrogen bonding. This is why substances like salt or sugar dissolve readily in water. Here are some key points about polar substances:

• Polar substances have a distinct separation of charges within their molecules.
• They often dissolve well in other polar solvents, including water.
• They can be important in biological systems, where water is a common solvent.

Discovering how polar substances work helps us understand many natural and chemical processes, making it an essential concept in chemistry.

Acidic Substances

Acidic substances are characterized by their low pH levels, typically less than 7. They release hydrogen ions ( H^+ ) when dissolved in water, which is a key feature of acids. This process of releasing hydrogen ions helps define their acidity. You might wonder why acids don't repel water, and here's why:

Acids love to mix with water because they can dissociate and release their H^+ ions, which are carried away by water molecules. Some familiar examples of acidic substances include vinegar (acetic acid) and lemon juice (citric acid).

Essential points about acidic substances:

• They contain hydrogen ions, which contribute to their high reactivity.
• The strength of an acid is determined by its ability to donate hydrogen ions.
• Commonly used in our daily lives, from food preparation to cleaning.

Understanding acidic substances helps you grasp how they interact with other substances and play roles in everyday chemical reactions.

Basic Substances

Basic substances, often known as alkalines, have a high pH level above 7. They are known for their ability to accept hydrogen ions ( H^+ ), which makes them essential players in neutralizing acids. Although they interact with water, they do not repel it as hydrophobic substances do.

When dissolved in water, basic substances release hydroxide ions ( OH^- ) or accept H^+ ions, which affects their behavior in solution. Common examples include baking soda and ammonia.

Key characteristics of basic substances:

• They have the ability to neutralize acids, which is why they are used in antacids.
• They can feel slippery or soapy to the touch due to their chemical nature.
• Commonly found in household cleaning agents, due to their grease-cutting ability.

Knowing about basic substances is important for understanding their pH effects and applications in various fields.