My Science School

The minerals dissolved in sea water, which make it taste salty, lower the temperature at which the water will freeze. But at the temperatures found at the far north and south of the globe, the sea is frozen all the time. Further from the Poles, it may also freeze in winter. In fact, the North Pole is permanently frozen sea — there is no land beneath the ice.

Ocean water freezes just like freshwater, but at lower temperatures. Fresh water freezes at 32 degrees Fahrenheit but seawater freezes at about 28.4 degrees Fahrenheit, because of the salt in it. When seawater freezes, however, the ice contains very little salt because only the water part freezes. It can be melted down to use as drinking water. At least 15 percent of the ocean is covered by sea ice some part of the year. On average, sea ice covers almost about 10 million square miles of the Earth.

Sea water becomes more and more dense as it becomes colder, right down to its freezing point. Fresh water, on the other hand, is most dense while still at 39.2 degrees Fahrenheit, well above the freezing point. The average temperature of all ocean water is about 38.3 degrees Fahrenheit.

If the temperature is cold enough, ocean water does freeze. The polar ice cap at earth's North Pole is a giant slab of frozen ocean water. At earth's South Pole, the land mass constituting Antarctica complicates the situation, so most of the ice there is compacted snow. Over cold regions such as Antarctica, Greenland, and Canada, the fresh water in the air freezes to snow and falls onto the land without a melting season to get rid of it. Over time, this snow builds up and compacts into an ice mass known as a glacier. Gravity slowly pulls the glacier downhill until it reaches out onto the ocean, forming an ice shelf. The ocean-bound edge of the ice shelf slowly crumbles into icebergs which float off on their own path. For this reason, glaciers, ice shelves, and icebergs are all thick sheets of frozen fresh water and not frozen ocean water. In contrast, when ocean water freezes, it forms a thin flat layer known as sea ice or pack ice. Sea ice has long been the enemy of ships seeking an open route through cold waters, but modern ice breaker ships have no problem breaking a path through the fields of frozen ocean.

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A refrigerator is basically a box that is very cold inside. The heat inside the box is made to move outside, where it flows out into the air. This is achieved by means of a pipe that contains a fluid called a refrigerant. The refrigerant flows around the pipe, becoming a vapour and then condensing back into a liquid. As it becomes a vapour, the refrigerant takes heat from inside the refrigerator.

The refrigerant, which is now in a liquid state, passes through the expansion valve and turns into a cool gas due to the sudden drop in pressure. As the cool refrigerant gas flows through the chiller cabinet, it absorbs the heat from the food items inside the fridge. The refrigerant, which is now a gas, flows into the compressor, which sucks it inside and compresses the molecules together to make it into a hot, high-pressure gas.

Now, this gas transports to the condenser coils (thin radiator pipes) located at the back of the fridge, where the coils help dissipate its heat so that it becomes cool enough to condense and convert back into its liquid phase. Because the heat collected from the food items is given off to the surroundings via the condenser, it feels hot to the touch.

After the condenser, the liquid refrigerant travels back to the expansion valve, where it experiences a pressure drop and once again becomes a cool gas. It then absorbs heat from the contents of the fridge and the whole cycle repeats itself.

Parts of a refrigerator

A refrigerator consists of a few key components that play a vital role in the refrigeration process:

Expansion valve

Also referred to as the flow control device, an expansion valve controls the flow of the liquid refrigerant (also known as ‘coolant’) into the evaporator. It’s actually a very small device that is sensitive to temperature changes of the refrigerant.

Compressor

The compressor consists of a motor that ‘sucks in’ the refrigerant from the evaporator and compresses it in a cylinder to make a hot, high-pressure gas.

Evaporator

This is the part that actually cools the stuff kept inside a refrigerator. It consists of finned tubes (made of metals with high thermal conductivity to maximize heat transfer) that absorb heat blown through a coil by a fan. The evaporator absorbs heat from the stuff kept inside, and as a result of this heat, the liquid refrigerant turns into vapor.

Condenser

The condenser consists of a coiled set of tubes with external fins and is located at the rear of the refrigerator. It helps in the liquefaction of the gaseous refrigerant by absorbing its heat and subsequently expelling it to the surroundings. As the heat of the refrigerant is removed, its temperature drops to condensation temperature, and it changes its state from vapor to liquid.

A homologous series is a group of compounds that are made of the same elements and share some of the same properties and features but have different numbers of atoms in their molecules. Alkanes, alkenes and alcohols all form homologous series.

Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member by CH2. Carbon chains of varying length have been observed in organic compounds having the same general formula. Such organic compounds that vary from one another by a repeating unit and have the same general formula form a series of compounds. Alkanes with general formula CnH2n+2, alkenes with general formula CnH2n and alkynes with general formula CnH2n-2 form the most basic homologous series in organic chemistry.

The successive members vary from each other by a CH2 unit. For example in CH4 and C2H6, the difference is -CH2 unit and the difference between C2H6 and C3H8   is also -CH2 unit. So CH4, C2H6, and C3H8 are homologs. The same thing can be observed in case of alkenes in which the first member is ethene and the successive members are C3H6, C4H8, and C5H10. They differ from each other by a –CH2 unit. Alkene formula is written as CnH2n.

All the members belonging to this series have the same functional groups. They have similar physical properties that follow a fixed gradation with increasing mass. The properties of CH3OH, C2H5OH, and C3H7OH are similar and follow a gradual change with increasing molecular mass of the successive members of the series. This is because, with the increase in the molecular mass of the compounds, the number of bonds also increases. Therefore, properties such as melting and boiling point, solubility, etc. that depend on the mass and the total number of bonds in a compound show a gradual change with an increase in molecular masses of the compounds. Chemical properties of the members of a homologous series are the same due to the fact that they all have the same functional groups in them.

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Carboxylic acids contain carbon, oxygen and hydrogen. Many naturally occurring acids are carboxylic acids, such as the acid that causes nettles to “sting” and the acid in vinegar. This is called thionic acid. It is created when alcohol reacts with oxygen (oxidizes).

Carboxylic acids with low molecular weights dissolve in water because the carboxyl group forms several hydrogen bonds with water. A carboxylic acid acts both as a hydrogen bond donor through its hydroxyl hydrogen atom and as a hydrogen bond acceptor through the lone pair electrons of both oxygen atoms. The solubility of carboxylic acids, like that of alcohols, decreases with increasing chain length because long nonpolar hydrocarbon chains dominate the physical properties of the acid.

Carboxylic acids dissolve in common alcohol solvents such as ethanol. This solubility results from intermolecular hydrogen bonds between solute and solvent, and from van der Waals attractions between the ethyl group of ethanol and the nonpolar tail of the carboxylic acid. Nonpolar solvents, such as chloroform, are also excellent solvents for carboxylic acids. In these solvents, the carboxylic acids exist as relatively nonpolar hydrogen-bonded dimers that are compatible with the solvent.

Carboxylic acids are characterized by the strong absorption due to the carbonyl group in the infrared spectra of these compounds. The absorption occurs in the same region as the carbonyl groups of aldehydes and ketones, but the absorption for carboxylic acids occurs at slightly higher wavenumber, and tends to be somewhat broadened. The O—H bond of carboxylic acids absorbs in the same region as that for alcohols. However, the absorption is very much broader for carboxylic acids, and it overlaps the C—H absorptions.

Some carboxylic acids are found in fats and oils from animals and plants. They are called fatty acids. When they react with alcohol, they create compounds called esters, which give flowers their scent. Some expensive perfumes are still made by distilling the scent from flowers and preserving it in alcohol.

Carbon is an essential element in all living things. It is constantly being recycled on Earth in the carbon cycle.

Carbon is the foundation of all life on Earth, required to form complex molecules like proteins and DNA. This element is also found in our atmosphere in the form of carbon dioxide (CO2). Carbon helps to regulate the Earth’s temperature, makes all life possible, is a key ingredient in the food that sustains us, and provides a major source of the energy to fuel our global economy.

The carbon cycle describes the process in which carbon atoms continually travel from the atmosphere to the Earth and then back into the atmosphere. Since our planet and its atmosphere form a closed environment, the amount of carbon in this system does not change. Where the carbon is located — in the atmosphere or on Earth — is constantly in flux.

On Earth, most carbon is stored in rocks and sediments, while the rest is located in the ocean, atmosphere, and in living organisms. These are the reservoirs, or sinks, through which carbon cycles. Carbon is released back into the atmosphere when organisms die, volcanoes erupt, fires blaze, fossil fuels are burned, and through a variety of other mechanisms.

In the case of the ocean, carbon is continually exchanged between the ocean’s surface waters and the atmosphere, or is stored for long periods of time in the ocean depths. Humans play a major role in the carbon cycle through activities such as the burning of fossil fuels or land development. As a result, the amount of carbon dioxide in the atmosphere is rapidly rising; it is already considerably greater than at any time in the last 800,000 years.

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It is likely that the effects of alcohol were discovered before the chemical! Grapes may have natural yeast on their skins that will cause the fruits or juice squeezed from them to ferment in warm conditions without the addition of further yeast. Early peoples may have discovered that fermented grape juice had an unusual flavour and effect on the body.

It’s hard to say exactly when alcohol was discovered for two reasons: 1) it was a long time ago, and 2) because you have to imagine that noting the date and time was not the first thing that occurred to the discoverers.

The first mistake that needs to be cleared up is that, while the origin may be in dispute, there is no doubt that alcohol – or fermentation, at least – was discovered rather than “invented.” One does not invent a thing that occurs naturally, as fermentation most assuredly does. (To illustrate this fact it should be pointed out that humans are not the only animals that enjoy a drink or two. A recent study published in the Proceedings of the National Academy of Sciences discusses the discovery of a few mammals in the Malaysian rainforest that drink the fermented nectar of what’s known as the bertam palm flower.)

Regarding human discovery, some paleontologists trace the origin all the way back to the Neolithic period, and some even believe that it was alcohol – or the desire for it – that prompted the first humans to take up agriculture.

Perhaps unsurprisingly, humanity’s love of alcohol has also been credited for precipitating the creation of democracy and the American Revolution. Of course, these things are spoken of in just, but if one seriously considers the integral part of alcohol in some of history’s most momentous decisions and accomplishments … well, it’s a sobering thought to say the least.

When it comes to intentional brewing the historical record is nearly as muddled. Anthropologists know people were drinking beer in Mesopotamia in 4,000 BC because there are records of it being traded, and Sumerians sang odes to it as far back as 1,800 BC, but many scientists believe the history of brewing stretches back much further.

Alcohol distillation, however, is probably a bit younger in the tooth according to most historians. Mesopotamians were known to use the distillation process, but it would take a few hundred years before the Chinese would use it to make rice liquor.

The final conclusion: booze has been around forever in some shape or form, and we’ll never really know the exact date and time that one lucky human made the discovery of a lifetime.

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Fermentation is a natural process that uses a kind of fungus called yeast. When given the right conditions of warmth and moisture, yeast will digest sugars in fruit or other plant materials and give off carbon dioxide gas and alcohol. Fermentation is used on a huge scale to make alcoholic drinks and ethanol for use in industry.

Alcoholic fermentation is the best known of the fermentation processes, and is involved in several important transformation, stabilization, and conservation processes for sugar-rich substrates, such as fruit, and fruit and vegetable juices. Alcoholic fermentation is carried out by yeasts and some other fungi and bacteria. The first step of the alcoholic fermentation pathway involves pyruvate, which is formed by yeast via the EMP pathway, while it is obtained through the ED pathway in the case of Zymomonas (bacteria). In the following step, the pyruvate is decarboxylated to acetaldehyde in a reaction that is catalyzed by the enzyme pyruvate decarboxylase.

Alcoholic fermentation is a biotechnological process accomplished by yeast, some kinds of bacteria, or a few other microorganisms to convert sugars into ethyl alcohol and carbon dioxide. In this fermentation process, yeast is mostly used as a bio-culture and aqueous solution of monosaccharide (raw materials) as the culture media for the production of beverages. In the alcoholic fermentation process, yeast generally carries out the aerobic fermentation process, but it may also ferment the raw materials under anaerobic conditions. In the absence of oxygen, alcoholic fermentation occurs in the cytosol of yeast. Alcoholic fermentation begins with the breakdown of sugars by yeasts to form pyruvate molecules, which is also known as glycolysis. Glycolysis of a glucose molecule produces two molecules of pyruvic acid. The two molecules of pyruvic acid are then reduced to two molecules of ethanol and 2CO2.

Alcohol is an organic compound. That means that it is one of the substances studied in a whole branch of chemistry called organic chemistry. Organic chemistry concerns carbon compounds, many of which are made by living (organic) things. Alcohol is a compound of carbon, oxygen and hydrogen. There are many kinds of alcohol, with different properties and uses in industry. Ethanol and glycerol are both useful forms of alcohol.

Alcohol is formed when yeast ferments (breaks down without oxygen) the sugars in different food. For example, wine is made from the sugar in grapes, beer from the sugar in malted barley (a type of grain), cider from the sugar in apples, vodka from the sugar in potatoes, beets or other plants.

Alcohol is classed as a ‘sedative hypnotic’ drug, which means it acts to depress the central nervous system at high doses. At lower doses, alcohol can act as a stimulant, inducing feelings of euphoria and talkativeness, but drinking too much alcohol at one session can lead to drowsiness, respiratory depression (where breathing becomes slow, shallow or stops entirely), coma or even death.

As well as its acute and potentially lethal sedative effect at high doses, alcohol has effects on every organ in the body and these effects depend on the blood alcohol concentration (BAC) over time.

It is classed as a depressant, meaning that it slows down vital functions—resulting in slurred speech, unsteady movement, disturbed perceptions and an inability to react quickly. As for how it affects the mind, it is best understood as a drug that reduces a person’s ability to think rationally and distorts his or her judgment.

Although classified as a depressant, the amount of alcohol consumed determines the type of effect. Most people drink for the stimulant effect, such as a beer or glass of wine taken to “loosen up.” But if a person consumes more than the body can handle, they then experience alcohol’s depressant effect. They start to feel “stupid” or lose coordination and control.

Alcohol overdose causes even more severe depressant effects (inability to feel pain, toxicity where the body vomits the poison, and finally unconsciousness or, worse, coma or death from severe toxic overdose). These reactions depend on how much is consumed and how quickly.

There are different kinds of alcohol. Ethyl alcohol (ethanol), the only alcohol used in beverages, is produced by the fermentation of grains and fruits. Fermenting is a chemical process whereby yeast acts upon certain ingredients in the food, creating alcohol.

Fermented drinks, such as beer and wine, contain from 2% alcohol to 20% alcohol. Distilled drinks, or liquor, contain from 40% to 50% or more alcohol.

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Diamond mines produce both gem-quality and industrial diamonds. Although most of the diamonds sold are industrial diamonds, the value of the gem diamond trade is much greater. Africa is the richest continent for diamond mining, accounting for around 49 per cent of world production. Artificial diamonds are made for use in industry. Most artificial diamonds are made in the United States.

A total of only 314 tonnes of diamond has ever been mined in the whole history of diamond mining. The world’s total of all gems, industrial, natural and synthetic is around 57 tonnes per year.

The world’s famous diamonds

The Star of Africa is the world’s largest cut diamond. It was cut from the biggest diamond ever found and is included in the British Crown Jewels. The Smithsonian pink diamond, although small, is extremely valuable because of its unusual colour.

Weighing gemstones

Diamonds and other gemstones are weighed in a special unit. This is called a ‘carat’. There are five carats (cts) in one gramme. Therefore 1 kg is 5,000 cts. Tiny diamonds have their own measure. They are weighed in ‘points’. One carat is 100 points, so a quarter-carat gem (0.25 ct) is a ‘twenty-five pointer’. Gold is also measure in carats but these are not based on weight. They are amounts of gold in metal, and 24 carats is equivalent to 100 per cent pure gold.

Testing for hardness

By comparing other stones with the hardness of a diamond, a test called the ‘hardness test’ was developed. Minerals can be tested by measuring their hardness. In the diagram, the hardness value of several different substances is given. This is called the Mohs scale and measures hardness from one, representing talc, to ten — diamond — with the highest hardness value.

Calcite is a colourless mineral found in limestone; gypsum is a white mineral and is used for making plaster.

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Gemstones play an important part in our lives. We use gems in medicine, space travel, weather forecasting, and engineering in industry. Without them we would not be able to drill into the Earth’s crust to extract oil, which has numerous uses in today’s world. However, the extraction of gemstones can cause a number of environmental problems.

Wildlife

During the mining process, large areas of vegetation are cleared to allow for the exploration of the area, the actual mining and the processing of the gemstones retrieved from the mine. As a result, the animals and plants in the area are wiped out.

Pollution

The heavy digging and lifting machines used in the mining industry pump out carbon monoxide, hydrogen and oxides of nitrogen and sulphur. These can be harmful to humans and wildlife. The carbon monoxide is converted into carbon dioxide in the atmosphere. This contributes to the greenhouse effect — global warming — which could devastate our planet if it is not controlled.

Waste

Usually, a lump of rock bigger than a house must be crushed and sorted to find one small gem. This waste must be disposed of safely so that it does not cause further damage to wildlife. The crushing of waste rock also produces a lot of dust, which can hang in the air, making breathing uncomfortable. Water drainage from mining processes carries acidic waste products into rivers, causing harm to the local ecosystem.

Rarity

Many gems are rare. Even gems that are thought of as common, such as amethyst, are rare compared to most rocks in the Earth’s crust. To conserve these rare stones, scientists have found ways of creating artificial gemstones, mainly for use in industry.

The future

To protect the environment from damage caused by gemstone mining, it must be managed properly. This means that governments and mining companies must stick to rules that encourage waste to be disposed of safely. They must also limit destruction of ecologically important areas, such as habitats that contain endangered species of plant or animal life.

 

Gems have played an important part in medicine since around the 1960s. Rubies are used to produce a laser beam in certain types of lasers. Ruby lasers are used in the removal of skin blemishes, such as tattoos. However, there can be side-effects to this treatment, such as scarring and a removal of natural skin colour in the area.

Diamond has many special properties. Hard diamond chips are used on dental drills to allow them to cut easily through teeth. Many kinds of radiation can travel easily through diamond and it can withstand huge pressures. This makes it suitable for use in space, and in weather and spy satellites. Perfect diamonds are used on space probes, as they are unlikely to be damaged by the deadly gases found on some planets, such as Venus.

Quartz is often used in precision instruments. Scientists discovered that when quartz crystals are put in an electric field, they will vibrate. The precise way in which the quartz is cut affects the speed at which it vibrates. This exact vibration is used as the beat to keep time in a ‘quartz’ clock or watch. Tiny ‘jewel’ bearings, often rubies, are fitted inside clockwork watches. They are used because their surfaces are not worn away by the workings of the watch.

High-quality natural diamonds are used to make fine scalpel blades for surgeons to use in delicate eye operations. The precision-made stylus in a record player pick-up is also a diamond and therefore lasts for a long time. Heat flows through diamond very easily, so tiny diamond pieces are used in television transmitters to keep electronic devices cool.

A quartz watch

In a quartz watch, a battery produces electric pulses. These electric pulses ‘wobble’ the quartz. As long as the battery continues to do this, the quartz will ‘wobble’ at an exact rate to create a steady pulse. This helps to keep the watch showing the correct time.

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Diamond is harder than any other substance. It can cut through anything. For this reason it has many uses in industry. Diamond powder is used for polishing lenses and gems, and for sawing tiny silicon wafers to make computer chips. Diamond is used in drills to make holes in stone and concrete. Whole ‘stones’ are used for engraving glass, as teeth in large saws for slicing stone and as drills powerful enough to cut holes in road surfaces. They are also set into the drills of oil and gas wells exploring under the sea bed.

In the future, diamonds may be used to make very small and powerful computers, radiation detectors, unwettable and unscratchable surfaces and as light emitters in electronic displays.

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Some types of gems are made as imitations of more valuable gemstones. Often, cheaper natural gems that look similar are used. For example, citrine looks like the more costly topaz. Sometimes, artificial gems are used.

‘Gemologists’ test gems and crystals to find out exactly what they are made of. They have to look closely inside the gem through a lens or a microscope. They also test the quality of light coming out of a gem and can tell whether the sapphire is artificial or natural.

Gemstones can be sandwiched together with other substances to create ‘gems’ that can be sold for more than they are really worth. This method is also used to create cheaper jewellery.

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