Matter and its Properties - SS1 Chemistry Past Questions and Answers - page 2

Matter can be classified into different categories based on its physical and chemical properties. This classification helps scientists understand and organise the vast diversity of substances found in the universe. The main classifications of matter based on physical and chemical properties are elements, compounds, and mixtures.

 

Elements are pure substances that consist of only one type of atom. They cannot be broken down into simpler substances by ordinary chemical means. Each element is uniquely defined by its atomic number, which represents the number of protons in the nucleus of its atoms. Elements are listed in the periodic table, where they are arranged based on their atomic numbers and similar properties. Examples of elements include oxygen, hydrogen, carbon, and gold.

 

Compounds are substances composed of two or more different elements chemically combined in fixed proportions. They have distinct chemical and physical properties different from their constituent elements. Compounds can be broken down into simpler substances through chemical reactions. Water (H2O), carbon dioxide (CO2), and table salt (NaCl) are examples of compounds. The ratio of atoms in a compound is represented by its chemical formula.

 

Mixtures are combinations of two or more substances that are physically mixed together but not chemically bonded. Unlike compounds, the substances in a mixture retain their individual properties and can be separated by physical means. Mixtures can be further classified into homogeneous and heterogeneous mixtures. Homogeneous mixtures, also known as solutions, have a uniform composition throughout, such as salt dissolved in water. Heterogeneous mixtures have visibly distinct components, like a salad with various vegetables.

 

Colloids are a special type of mixture characterised by intermediate particle size between those of solutions and suspensions. In colloids, particles are dispersed in a medium but do not settle out due to their small size and the continuous motion of the surrounding particles. Examples of colloids include milk, fog, and gelatin.

 

In summary, matter can be classified based on its physical and chemical properties into elements, compounds, and mixtures. Elements consist of only one type of atom, compounds are composed of different elements chemically combined, and mixtures are combinations of substances that can be physically separated. Understanding the classification of matter based on its properties is crucial for scientists to study and manipulate substances for various applications in fields such as chemistry, physics, and materials science.