What are Properties of Covalent Compounds?

S6-SA4-0022

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

Covalent compounds are formed when atoms share electrons to achieve stability. Their properties, like low melting points and poor conductivity, are a direct result of these shared electron bonds.

Simple Example

Quick Example

Think about how your mobile phone's screen guard sticks to the screen. It's not a super strong glue, but it holds well enough for everyday use. Similarly, the forces holding molecules in a covalent compound are strong within the molecule, but weaker between different molecules, making them easier to separate.

Worked Example

Step-by-Step

Let's understand why water (H2O), a covalent compound, has a relatively low boiling point compared to salt (NaCl), an ionic compound.

1. **Identify the bonds:** In water, hydrogen atoms share electrons with oxygen atoms to form H-O bonds within each water molecule. These are strong covalent bonds.
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2. **Identify intermolecular forces:** Between different water molecules, there are weaker forces called hydrogen bonds. These are not as strong as the covalent bonds *within* the molecule.
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3. **Compare with ionic compounds:** In salt, positive sodium ions (Na+) and negative chloride ions (Cl-) are held together by very strong electrostatic forces throughout the entire crystal lattice.
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4. **Energy required for boiling:** To boil water, we only need enough energy to break the *weaker* forces between water molecules (intermolecular forces), allowing them to escape as gas.
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5. **Energy required for melting/boiling salt:** To melt or boil salt, we need to break the *very strong* electrostatic forces holding the ions together, which requires much more energy.
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6. **Conclusion:** Because less energy is needed to overcome the weaker intermolecular forces in water, it boils at 100 degrees Celsius, which is much lower than the melting point of salt (801 degrees Celsius). This shows water's covalent nature leads to a lower boiling point.

Answer: Water, being a covalent compound, has weaker intermolecular forces requiring less energy to overcome, leading to a lower boiling point compared to ionic compounds like salt.

Why It Matters

Understanding covalent properties is key in fields like Medicine for designing new drugs, and in Biotechnology for creating advanced materials. Engineers use this knowledge to develop new plastics and composites, which are essential for everything from car parts to space technology.

Common Mistakes

MISTAKE: Thinking covalent compounds always have high melting and boiling points because the bonds *within* the molecules are strong. | CORRECTION: The bonds *within* a covalent molecule are strong, but the forces *between* different molecules are usually weak, leading to lower melting/boiling points.

MISTAKE: Believing covalent compounds conduct electricity well because they have electrons. | CORRECTION: Covalent compounds do not have free ions or free electrons to carry charge, so most of them are poor conductors of electricity.

MISTAKE: Assuming all covalent compounds are gases or liquids at room temperature. | CORRECTION: While many are, some covalent compounds, like sugar or plastics, are solids at room temperature. Their state depends on the strength of their intermolecular forces.

Practice Questions

Try It Yourself

QUESTION: Why is sugar (a covalent compound) soluble in water, but oil (also a covalent compound) is not? | ANSWER: Sugar is soluble in water because it can form hydrogen bonds with water molecules (like dissolves like). Oil is non-polar and cannot form these bonds with polar water, so it doesn't dissolve.

QUESTION: A substance melts at 80 degrees Celsius and does not conduct electricity when melted. Is it likely an ionic or covalent compound? Explain. | ANSWER: It is likely a covalent compound. Ionic compounds typically have very high melting points (above 300-400 degrees Celsius) and conduct electricity when melted (due to free ions). The low melting point and non-conductivity suggest a covalent nature.

QUESTION: You are given two unknown substances, A and B. Substance A is a white solid that dissolves in water and conducts electricity when dissolved. Substance B is a clear liquid that does not conduct electricity. Identify the probable bond type for each and list one other property for each. | ANSWER: Substance A is likely an ionic compound (high melting point, dissolves to form ions, conducts electricity). Another property: often crystalline solids. Substance B is likely a covalent compound (low melting/boiling point, does not conduct electricity). Another property: often exists as liquids or gases at room temperature.

MCQ

Quick Quiz

Which of the following is NOT a typical property of covalent compounds?

Low melting and boiling points

Generally poor conductors of electricity

Strong intermolecular forces

Often soluble in non-polar solvents

The Correct Answer Is:

Covalent compounds typically have *weak* intermolecular forces, not strong ones. This is why they generally have low melting and boiling points. Options A, B, and D are all typical properties.

Real World Connection

In the Real World

Many everyday materials like plastics (used in water bottles, toys), cooking oils, and even the natural gas (methane) used in our homes for cooking are covalent compounds. The way these materials behave – like plastic being flexible or oil not mixing with water – is all due to their covalent properties.

Key Vocabulary

Key Terms

COVALENT BOND: A chemical bond formed by the sharing of electrons between atoms. | INTERMOLECULAR FORCES: Weak attractive forces between separate molecules. | MELTING POINT: The temperature at which a solid turns into a liquid. | BOILING POINT: The temperature at which a liquid turns into a gas. | CONDUCTIVITY: The ability of a substance to allow electricity or heat to pass through it.

What's Next

What to Learn Next

Now that you understand covalent properties, you should explore 'Ionic Compounds and Their Properties'. This will help you compare and contrast the two major types of chemical bonds and see how different bonding leads to vastly different material behaviors.