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- Бұл бет үшін навигация:
- Atomic structure
- Radioactivity. Nuclear reactions
- Natural resources and power Natural resources
- Raw materials
- Power resources
Substances Substances are distinguished by their properties – colour, smell, taste, specific gravity, greater or lesser hardness, melting and boiling points, volatility, etc. For example, in describing the properties of sugar, one can state that sugar is a hard, brittle substance, white in colour, sweet to the taste, without odour, easily soluble in water, heavier than water and it turns brown when it is heated, etc. In order to learn the properties of a substance one must have it in its pure form. Even small admixtures of foreign substances may change the properties of a substance. For example: pure water is both colourless and transparent, but if a drop of milk is added to a glass of water, the water becomes clouded; if a drop of ink is added, the water becomes coloured. All the enumerated properties are not those of water but they are the properties of the admixtures. In some cases, one may see at once that a substance is heterogeneous, that is, a mixture of different substances. Granite, cement, petroleum are examples of non-homogeneous materials; they consist of mixtures of substances. Thus, granite is a mixture of varying quantities of silica, feldspar, and mica, each of which possesses its own set of properties. Coal is not a substances too because different samples contain different relatives amounts of ash, water, carbon, and other components. Every materials, therefore, consists of a single (pure) substance, or it is a mixture of two or more substances, each of which retains in the mixture its own characteristic properties. 576
Atomic structure What Is an Element? An element is a pure substance that cannot be broken down by chemical methods into simpler components. For example, the element gold cannot be broken down into anything other than gold. If you kept hitting gold with a hammer, the pieces would get smaller, but each piece will always be gold. You can think of each kind of element having its own unique fingerprint making it different than other elements. Elements consist of only one type of atom. An atom is the smallest particle of an element that still has the same properties of that element. All atoms of a specific element have exactly the same chemical makeup, size, and mass. There are a total of 118 elements, with the most abundant elements on Earth being helium and hydrogen. Many elements occur naturally on Earth; however, some are created in a laboratory by scientists by nuclear processes. Elements Are Written as Symbols Instead of writing the whole elemental name, elements are often written as a symbol. For example, O is the symbol for oxygen, C is the symbol for carbon, and H is the symbol for hydrogen. Not all elements have just one letter as the symbol, but have two letters - like Al is the symbol for aluminum and Ni is the symbol for nickel. The first letter is always capitalized, but the second letter is not. Symbol names do not always match the letters in the elemental name. For example, Fe is the symbol for iron and Au is the symbol for gold. These symbol names are derived from the Latin names for those elements. Radioactivity. Nuclear reactions Radioactivity was discovered in 1896 by the French scientist Henri Becquerel, while working with phosphorescent materials. These materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it. All results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper. These radiations were given the name "Becquerel Rays". It soon became clear that the blackening of the plate had nothing to do with phosphorescence, as the blackening was also produced by non-phosphorescent salts of uranium and metallic uranium. It became clear from these experiments that there was a form of invisible radiation that could pass through paper and was causing the plate to react as if exposed to light. At first, it seemed as though the new radiation was similar, then recently discovered X-rays. Further research by Becquerel, Ernest Rutherford, Paul Villard, Pierre Curie, Marie Curie, and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were the first to realize that many decay processes resulted in the transmutation of one element to another. Subsequently, the 577
radioactive displacement law of Fajans and Soddy was formulated to describe the products of alpha and beta decay. The early researchers also discovered that many other chemical elements, besides uranium, have radioactive isotopes. A systematic search for the total radioactivity in uranium ores also guided Pierre and Marie Curie to isolate two new elements: polonium and radium. Except for the radioactivity of radium, the chemical similarity of radium to bariummade these two elements difficult to distinguish. Marie and Pierre Curie’s study of radioactivity is an important factor in science and medicine. After their research on Becquerel's rays led them to the discovery on both radium and polonium, they coined the term "radioactivity." Their research on the penetrating rays in uranium and discovery of radium launched an era of using radium for treatment of cancer. Their exploration of radium could be seen as the first peaceful use of nuclear energy and the start of modern nuclear medicine. A nuclear reaction is considered to be the process in which two nuclear particles (two nuclei or a nucleus and a nucleon) interact to produce two or more nuclear particles or X-rays (gamma rays). Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. Sometimes if a nucleus interacts with another nucleus or particle without changing the nature of any nuclide, the process is referred to a nuclear scattering, rather than a nuclear reaction. Perhaps the most notable nuclear reactions are the nuclear fusion reactions of light elements that power the energy production of stars and the Sun. Natural nuclear reactions occur also in the interaction between cosmic rays and matter. The most notable man-controlled nuclear reaction is the fission reaction which occurs in nuclear reactors. Nuclear reactors are devices to initiate and control a nuclear chain reaction, but there are not only manmade devices. The world’s first nuclear reactor operated about two billion years ago. The natural nuclear reactor formed at Oklo in Gabon, Africa, when a uranium-rich mineral deposit became flooded with groundwater that acted as a neutron moderator, and a nuclear chain reaction started. These fission reactions were sustained for hundreds of thousands of years, until a chain reaction could no longer be supported. This was confirmed by existence of isotopes of the fission-product gas xenon and by different ratio of U-235/U-238 (enrichment of natural uranium).  
Natural resources and power Natural resources Natural resources are resources that exist without the actions of humankind. This includes all valued characteristics such as magnetic, gravitational, and electrical 578
properties and forces. On earth we include sunlight, atmosphere, water, land, air (includes all minerals) along with all vegetation and animal life that naturally subsists upon or within therefore identified characteristics and substances. Natural resources may be further classified in different ways. Natural resources are materials and components (something that can be used) that can be found within the environment. Every man-made product is composed of natural resources (at its fundamental level). A natural resource may exist as a separate entity such as fresh water, and air, as well as a living organism such as a fish, or it may exist in an alternate form which must be processed to obtain the resource such as metal ores, mineral oil, and most forms of energy. There is much debate worldwide over natural resource allocations; this is particularly true during periods of increasing scarcity and shortages (depletion and overconsumption of resources) but also because the exportation of natural resources is the basis for many economies (particularly for developed countries). Some natural resources such as sunlight and air can be found everywhere, and are known as ubiquitous resources. However, most resources only occur in small sporadic areas, and are referred to as localized resources. There are very few resources that are considered inexhaustible (will not run out in foreseeable future) – these are solar radiation, geothermal energy, and air (though access to clean air may not be). The vast majority of resources are theoretically exhaustible, which means they have a finite quantity and can be depleted if managed improperly. In recent years, the depletion of natural resources has become a major focus of governments and organizations such as the United Nations. This is evident in the UN's Agenda 21 Section Two, which outlines the necessary steps to be taken by countries to sustain their natural resources. The depletion of natural resources is considered to be a sustainable development issue. The term sustainable development has many interpretations, most notably the Brundtland Commission's 'to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs', however in broad terms it is balancing the needs of the planet's people and species now and in the future. In regards to natural resources, depletion is of concern for sustainable development as it has the ability to degrade current environments and potential to impact the needs of future generations. The conservation of natural resources is the fundamental problem. Unless we solve that problem, it will avail us little to solve all others. Natural resources can be consumed directly or indirectly. For instance, humans depend directly on forests for food, biomass, health, recreation and increased living comfort. Indirectly forests act as climate control, flood control, storm protection and nutrient cycling. Raw materials Sometimes, natural resources can be used as raw materials to produce something. For instance, we can use a tree from the forest to produce timber. The timber is then used to produce wood for furniture or pulp for paper and paper products. In this scenario, the tree is the raw material. 579
Every item in your home was made from a raw material that came from a natural resource. The tea mug, electricity at home, bread, clothes, you name them: each of them came from a natural resource. Natural resources come in many forms. It may be a solid, liquid or gas. It may also be organic or inorganic. It may also be metallic or non-metallic. It may be renewable or non-renewable. Renewable and Non-renewable Resources All natural resources fall under two main categories: renewable and non-renewable resources. The table below will help us understand this better. Renewable resources Renewable resources are those that are constantly available (like water) or can be reasonably replaced or recovered, like vegetative lands. Animals are also renewable because with a bit of care, they can reproduce off springs to replace adult animals. Even though some renewable resources can be replaced, they may take many years and that does not make them renewable. If renewable resources come from living things, (such as trees and animals) they can be called organic renewable resources.
Non-renewable resources Non -renewable resources are those that cannot easily be replaced once they are destroyed. Examples include fossil fuels. Minerals are also non-renewable because even though they form naturally in a process called the rock cycle, it can take thousands of years, making it non-renewable. Some animals can also be considered non-renewable, because if people hunt for a particular species without ensuring their reproduction, they will be extinct. This is why we must ensure that we protect resources that are endangered. Non -renewable resources can be called inorganic resources if they come from non-living things. Examples include include, minerals, wind, land, soil and rocks. Some non-renewable resources come from living things — such as fossil fuels. They can be called organic non-renewable resources. Metallic and Non-metallic Resources Inorganic resources may be metallic or non-metallic. Metallic minerals are those that have metals in them. They are harder, shiny, and can be melted to form new products. Examples are iron, copper and tin. Non-metallic minerals have no metals in them. They are softer and do not shine. Examples include clay and coal. Why are Natural Resources so important? Natural resources are available to sustain the very complex interaction between living things and non-living things. Humans also benefit immensely from this interaction. All over the world, people consume resources directly or indirectly. Developed countries consume resources more than under-developed countries. In what form do people consume natural resources? The three major forms include food and drink, housing and infrastructure, and mobility. These three make up more than 60% of resource use. 580
Since 1933 the World Energy Council has published a report presenting statistics for reserves, and production of various resources at the global level. The World Energy Resources study group and its working groups collect and evaluate data on resources. It focuses on proven reserves, examines the evolving nature of the energy mix in countries worldwide and highlights emerging energy sources and technologies. The World Energy Resources report is a strategic publication of the World Energy Council prepared triennially and timed for release at each World Energy Congress. It offers a uniquely global perspective on twelve major resources. This highly regarded publication is an essential tool for governments, industry, investors, NGOs and academia.
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cross-cutting issues of, carbon capture and storage, energy efficiency and energy storage. These Knowledge Networks provide updated data for the website and publications, as well as working on timely deep-dives with a resource focus. An example of a magnetic force is the pull that attracts metals to the magnet. Now, the electrical field induced causes waves, called electromagnetic waves, and they can travel through a vacuum (air), particles or solids. These waves resemble the ripple (mechanical) waves you see when you drop a rock into a swimming pool, but with electromagnetic waves, you do not see them, but you often can see the effect of it. The energy in the electromagnetic waves is what we call radiant energy. There are different kinds of electromagnetic waves and all of them have different wavelengths, properties, frequencies and power, and all interact with matter differently. The entire wave system from the lowest frequency to the highest frequency is known as the electromagnetic spectrum. The shorter the wavelength, the higher its frequency and vice versa. White light, for example, is a form of radiant energy, and its frequency forms a tiny bit of the entire electromagnetic spectrum. What is radiant energy? When radiant energy comes into contact with matter, it changes the properties of that matter. For example, when micro-waves (which form part of the entire spectrum) are set off in a microwave oven, the water molecules in the food are charged and caused to vibrate billions of times per second, generating heat, that causes the food to cook. The microwave oven works with the concept of radiant energy (electromagnetic waves). Energy Stored Energy cannot be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery. When connected in a circuit, energy stored in the battery is released to produce electricity. Energy Stored If you look at a battery, it will have two ends: a positive terminal and a negative terminal. If you connect the two terminals with wire, a circuit is formed. Electrons will flow through the wire and a current of electricity is produced. Energy can also be stored in many other ways. Batteries, gasoline, natural gas, food, water towers, a wound up alarm clock, a Thermos flask with hot water and even pooh are all stores of energy. They can be transferred into other kinds of energy. 
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