Ch 16Green Chemistry and Nanochemistry — Class 12 Chemistry, concept-first.

Chemistry has done a great deal to improve the quality of everyday life, but that same progress has put human health and the global environment under threat.

Green chemistry plays an important role in achieving sustainable development, and adopting its twelve principles is presented as the practical route to that goal.

Green Chemistry itself is defined as the use of chemistry for pollution prevention, through the environmentally conscious design of chemical products and processes that reduce or eliminate the use or…

The first principle gives priority to preventing waste from being created in the first place, rather than treating or cleaning it up after a chemical process has already generated it.

Atom economy measures how much of the mass of the starting materials ends up in the useful, desired product at the end of a chemical process, rather than being lost to unwanted byproducts.

The third principle calls for chemical reactions and synthesis routes to be designed to be as safe as possible, so that the formation of hazardous waste is avoided wherever a process can be redesigned…

Closely related to the previous principle, this one is about developing products that are inherently less toxic, or that can be made from less toxic raw materials, rather than only making the synthesi…

This principle asks chemists to choose the safest solvent available for each step of a reaction, and to minimise the total amount of solvents and auxiliary substances used overall, since solvents typi…

Chemical synthesis should be designed to minimise the amount of energy it consumes, and it is generally better to run reactions at, or close to, room temperature and pressure rather than under energy-…

This principle is directed largely at petrochemicals: wherever possible, chemicals should be made from renewable, plant-based sources rather than from non-renewable sources such as crude oil.

Organic synthesis commonly relies on protecting or blocking groups -- temporarily converting a reactive functional group into an unreactive one so that a different part of the molecule can be modified…

Using a catalyst in a chemical reaction speeds up its rate, and green chemistry's ninth principle is simply to prefer catalytic routes over stoichiometric ones wherever possible.

This principle asks chemists to design chemicals so that they degrade into harmless products and can be discarded easily once their useful life is over, and to ensure that both the original chemical a…

This principle calls for analytical methods to be developed and continually improved so that manufacturing and processing can be monitored and controlled in real time, in-process, rather than only bei…

The twelfth and final principle is to develop chemical processes that are inherently safer and that minimise the risk of accidents such as explosions, fires and harmful emissions.

Green chemistry's underlying premise is that the Earth does have a natural capacity for absorbing and dealing with much of the waste and pollution that society generates -- problems only arise, and so…

From the clothes and sunglasses people wear to computer hard drives and everyday cleaning products, nanotechnology plays a significant role in the manufacture of a huge range of materials -- lasers us…

Nanoscience is defined as the study of phenomena and the manipulation of materials at atomic, molecular and macromolecular scales, where the properties of matter differ significantly from the properti…

Nanotechnology is defined as the design, characterisation, production and application of structures, devices and systems achieved by deliberately controlling their shape and size at the nanometre scal…

The word 'nano' comes from the Greek for dwarf, though the actual nanometre scale is, in the chapter's own words, even smaller than what 'dwarf' might suggest.

A nanomaterial is defined as a material having structural components with at least one dimension in the nanometre scale, that is, in the range 1-100 nm.

Nanochemistry is defined as the combination of chemistry and nanoscience. It deals specifically with the designing and synthesis of materials at the nanoscale, across different sizes, shapes, structur…

What makes the science of the nanoscale genuinely special is that, at such a small scale, different physical laws come to dominate a material's behaviour compared with the laws that govern everyday, h…

Colour is an optical property that behaves noticeably differently at the nanoscale compared with the bulk.

A high surface-area-to-volume ratio is one of the most important characteristics of nanoparticles. If a bulk material is progressively subdivided into a group of smaller and smaller individual particl…

Because surface area increases as particle size decreases (Section 16.6.2), nanomaterial-based catalysts show markedly increased catalytic activity compared with the same substance in bulk form -- mor…

The melting point of a nanomaterial changes drastically compared with the bulk material's melting point, and this change itself depends on exactly how small the particles are -- melting point is not a…

Mechanical strength -- specifically hardness -- is also strongly size-dependent at the nanoscale. Nanosized copper and palladium clusters, with particle diameters in the 5-7 nm size range, have been f…

Electrical conductivity is another property observed to change at the nanoscale compared with bulk behaviour.

Having established what makes nanoparticles behave differently from bulk material (Section 16.6), the chapter turns to how nanomaterials are actually made and studied.

There are two fundamentally different approaches to synthesising nanomaterials. In the bottom-up approach, molecular components arrange themselves into progressively more complex assemblies, building…

The sol-gel process is a widely used wet-chemical method for synthesising nanomaterials, particularly oxide materials.

Once a nanomaterial has been synthesised, it needs to be analysed and characterised using appropriate analytical tools or techniques, since its useful nanoscale properties (Section 16.6) cannot simply…

This section presents photographs and labelled schematic diagrams of the actual instruments named in Table 16.1 (Section 16.7.3), giving the reader a visual sense of what the analytical equipment used…

Nanomaterials have actually been produced and used by humans for hundreds of years, well before anyone understood or described them as 'nanostructured' -- the scientific understanding of certain tradi…

Nanochemistry has already contributed to a large number of innovative products across many different disciplines, thanks to the unique physical, chemical, optical, structural and catalytic properties…

Nanotechnology brings genuine advantages across several sectors. In electronics and computing, it represents a revolution in device capability.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

Sample papers and previous-year board questions for this subject.