Grade 6 → Elements, Compounds, and Mixtures ↓
Properties of Compounds
Compounds are a core part of chemistry. Unlike elements, which are pure substances made of only one type of atom, compounds form when two or more elements combine chemically. Understanding the properties of compounds helps us understand how substances interact in the world around us.
What is a compound?
A compound is a substance that is formed when two or more elements are chemically joined together. This means that the atoms of these elements are linked by chemical bonds, forming a new substance that has its own unique properties.
For example, water (H2O
) is a compound made of hydrogen and oxygen. Although hydrogen and oxygen are gases at room temperature, water is a liquid. This new property of being a liquid comes from the combination of hydrogen and oxygen.
H2 + O → H2O
Characteristics of compounds
- Fixed structure: The proportion of each element in a compound is fixed. For example, water is always made up of two hydrogen atoms and one oxygen atom.
- Distinctive properties: The properties of a compound are different from those of the elements that make it up.
- Chemical changes: Compounds can be separated into their elements only by chemical changes, such as heating or chemical reactions.
Visual example: formation of sodium chloride
Let's learn about the formation of table salt, a common compound known as sodium chloride (NaCl
). Below is a simplified illustration of how sodium and chlorine atoms combine to form sodium chloride:
In this response:
- Sodium (Na) loses one electron to become positively charged.
- Chlorine (Cl) gains that electron and becomes negatively charged.
- Sodium chloride is formed by the attraction between positively charged sodium and negatively charged chlorine.
Types of compounds
Compounds may be broadly classified into two types:
Molecular compounds
Molecular compounds are formed by sharing electrons between non-metal atoms. A good example of this is water.
H2 + O → H2O
Each hydrogen atom shares electrons with the oxygen atom, resulting in a covalent bond.
Ionic compounds
Ionic compounds form when electrons transfer from one atom to another, creating ions. These ions attract each other and form a bond. Sodium chloride (table salt) is an example of an ionic compound.
Na + Cl → NaCl
In sodium chloride, sodium loses an electron to become a positively charged ion, and chlorine gains an electron to become a negatively charged ion.
Examples of compounds
Water (H2O
)
Water is perhaps the most well-known compound. It is essential to life and covers about 71% of the Earth's surface. Water's unique properties, such as its boiling and freezing point, surface tension, and ability to dissolve many substances, are quite different from those of its constituent elements hydrogen and oxygen.
Carbon dioxide (CO2
)
Carbon dioxide is a compound made of carbon and oxygen. It is a gas at room temperature and is used by plants to make oxygen during photosynthesis.
C + O2 → CO2
Methane (CH4
)
Methane is a simple hydrocarbon compound consisting of one carbon atom bonded to four hydrogen atoms. It is widely used as a fuel and is a primary component of natural gas.
C + H4 → CH4
How are compounds different from mixtures
It's important to distinguish between compounds and mixtures. Compounds are made up of elements combined in chemically definite proportions, while mixtures are made up of two or more substances that are mixed together without any chemical bonds.
For example, if you mix sand and salt, you get a mixture. Each component retains its properties and can be easily separated, such as with a sieve or water.
Conclusion
Understanding compounds and their properties helps us understand how they make up the world around us. From the water we drink to the air we breathe, compounds are essential to life and a variety of natural processes. By learning about compounds, you can better understand how chemistry plays an important role in our daily lives.