Module 94. Physical Chemistry in Daily Life

Physical Chemistry, a branch of chemistry that bridges the principles of physics and chemistry, deals with the study of how matter behaves on a molecular and atomic level and how chemical reactions occur. It explores the physical properties of molecules, the forces that act upon them, and the energy changes associated with their interactions. Though the subject is often regarded as theoretical, it has immense practical significance in daily life, influencing everything from food preparation and medicine to environmental processes and industrial applications.

Fundamental Concepts and Their Relevance

Physical chemistry revolves around several key concepts such as thermodynamics, kinetics, electrochemistry, spectroscopy, and surface chemistry. Each of these principles underpins everyday phenomena and modern technologies.

• Thermodynamics explains how energy changes during physical and chemical processes, such as cooking, refrigeration, or combustion.
• Kinetics studies the rates of chemical reactions, relevant to food preservation and metabolism.
• Electrochemistry governs batteries, electroplating, and corrosion.
• Surface chemistry explains adsorption, catalysis, and the working of detergents.
• Spectroscopy helps in analysing materials and detecting substances, crucial in medicine and industry.

These core principles manifest in numerous real-life contexts, making physical chemistry indispensable in understanding and improving daily human activities.

Role in Food and Cooking

Cooking is one of the most direct demonstrations of physical chemistry. When food is heated, chemical bonds break and reform, leading to new textures, flavours, and aromas.

• The Maillard reaction, which occurs between amino acids and reducing sugars, gives browned food its distinctive taste.
• Boiling, freezing, and evaporation involve changes in physical states governed by thermodynamic laws.
• The concept of colligative properties explains why adding salt lowers the freezing point of water, making it useful for de-icing or faster cooking.
• Emulsions and colloids, such as mayonnaise or milk, demonstrate the importance of surface chemistry in stabilising mixtures of immiscible liquids.

In baking, the generation of gas (usually carbon dioxide) by yeast or baking powder follows the principles of chemical kinetics and gas laws, directly influencing the texture and rise of the final product.

Applications in Medicine and Pharmacology

Physical chemistry plays a critical role in the formulation, storage, and action of medicines. Drug design and delivery rely on an understanding of chemical equilibrium, solubility, and diffusion.

• Osmosis and dialysis are governed by colligative properties, essential in biological processes and medical treatments such as kidney dialysis.
• The concept of pH and buffers helps in maintaining the body’s acid–base balance and in developing medicines compatible with physiological conditions.
• Spectroscopic techniques such as infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy are used to identify and analyse chemical compounds in pharmaceuticals.
• Thermodynamics and kinetics determine the stability and shelf-life of drugs, ensuring their effectiveness over time.

In addition, electrochemistry underlies the functioning of pacemakers, biosensors, and diagnostic tools like blood glucose meters.

Energy and Environmental Applications

Energy conversion, conservation, and storage are deeply rooted in physical chemistry. Combustion processes, used in engines and power plants, are explained by thermodynamic principles and reaction kinetics. Understanding enthalpy and entropy helps improve energy efficiency and develop alternative sources of energy.

• Electrochemical cells and fuel cells convert chemical energy into electrical energy, as seen in batteries used in vehicles and electronic devices.
• Photovoltaic cells, which convert sunlight into electricity, rely on the quantum theory of light and semiconductor chemistry.
• Catalysis, a key area of surface chemistry, reduces energy consumption and emissions in industrial processes.

Environmental protection also depends on physical chemistry. The study of gases helps in understanding atmospheric pollution and the greenhouse effect, while the absorption of pollutants on activated carbon is a surface phenomenon used in water and air purification.

Role in Cleaning and Household Activities

Everyday cleaning activities provide excellent examples of physical chemistry in action. Detergents, soaps, and shampoos function due to the principles of surface chemistry and colloid science.

• Soap molecules have hydrophobic tails and hydrophilic heads, which allow them to emulsify grease and oil in water.
• Adsorption plays a key role in removing impurities and odours.
• Bleaching agents act through redox reactions, breaking down coloured compounds into colourless substances.

The concept of intermolecular forces explains why water forms droplets or why certain materials absorb or repel moisture. Even the process of ironing clothes involves breaking and reforming hydrogen bonds in fibres, an application of thermodynamics at the molecular level.

Physical Chemistry in Technology and Industry

Modern technology and industrial progress are profoundly influenced by physical chemistry. The design of new materials, fuels, and electronic devices requires understanding molecular behaviour and energy interactions.

• Electroplating and galvanisation rely on electrochemical deposition for corrosion prevention and decorative purposes.
• The production of ammonia (Haber process) and sulphuric acid (Contact process) depends on catalysis and equilibrium principles.
• Corrosion prevention is based on redox reactions and the use of sacrificial anodes.
• In nanotechnology, surface phenomena and quantum mechanics are applied to design materials with unique electrical, magnetic, and optical properties.

In industries like textiles, paints, polymers, and cosmetics, understanding viscosity, diffusion, and surface tension is essential for product quality and performance.

In Transportation and Everyday Devices

Physical chemistry governs the operation of cars, aeroplanes, and everyday electronic devices. The internal combustion engine is an example of thermodynamics in practice, converting chemical energy from fuel into mechanical work. The lubrication of machinery involves understanding molecular interactions and viscosity, while airbags function based on gas laws and rapid exothermic reactions.
Batteries and rechargeable cells, from mobile phones to electric vehicles, depend on electrochemical reactions and the movement of ions between electrodes. Even simple devices like refrigerators operate on enthalpy changes and phase transitions governed by thermodynamic cycles.

Environmental and Biological Relevance

Physical chemistry also helps explain natural processes essential for life and environmental balance. Photosynthesis, for instance, is a photochemical process converting light energy into chemical energy. The carbon and nitrogen cycles depend on redox and equilibrium reactions that regulate atmospheric and soil chemistry.
In biological systems, enzymes act as catalysts, accelerating biochemical reactions without being consumed. Cellular respiration, muscle contraction, and even nerve impulse transmission involve thermodynamics, kinetics, and electrochemical gradients.

Significance and Future Perspective

Physical chemistry is not confined to laboratories or textbooks; it is embedded in every aspect of daily living. From the functioning of a smartphone battery to the metabolism in the human body, from industrial synthesis to climate studies, its applications are far-reaching and vital.
Advances in physical chemistry continue to drive innovation in renewable energy, green chemistry, and sustainable technologies. As global challenges such as pollution, climate change, and energy scarcity intensify, the principles of physical chemistry provide the scientific foundation for developing cleaner, more efficient solutions.