Battery

A battery is a device that converts chemical energy directly to electrical energy. It consists of one or more voltaic cells; each voltaic cell consists of two half cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the electrode to which anions (negatively-charged ions) migrate, i.e. the anode or negative electrode; the other half-cell includes electrolyte and the electrode to which cations (positively-charged ions) migrate, i.e. the cathode or positive electrode. In the redox reaction that powers the battery, reduction (addition of electrons) occurs to cations at the cathode, while oxidation (removal of electrons) occurs to anions at the anode. The electrodes do not touch each other but are electrically connected by the electrolyte, which can be either solid or liquid. Many cells use two half-cells with different electrolytes. In that case each half-cell is enclosed in a container, and a separator that is porous to ions but not the bulk of the electrolytes prevents mixing.

Enviromental concern

The widespread use of batteries has created many environmental concerns, such as toxic metal pollution. Battery manufacture consumes resources and often involves hazardous chemicals. Used batteries also contribute to electronic waste. Some areas now have battery recycling services available to recover some of the materials from used batteries. Batteries may be harmful or fatal if swallowed. Recycling or proper disposal prevents dangerous elements (such as lead, mercury, and cadmium) found in some types of batteries from entering the environment.

Explosion of battery

• Overcharging will cause the explosion of battery whch is attempting to charge a battery beyond its electrical capacity—can also lead to a battery explosion, leakage, or irreversible damage to the battery.
• misuse or malfunction of a battery, such as attempting to recharge a non-rechargeable battery, or short circuiting a battery.
  

Dry Ice

Dry ice, sometimes referred to as "card ice", is solid carbon dioxide. It is commonly used as a versatile cooling agent.
Dry ice sublimes, changing directly to a gas at atmospheric pressure. Its sublimation and deposition point is −78.5 °C (−109.3 °F). Its enthalpy of sublimation (ΔHsub) at −78.5 °C (−109.3 °F) is 571 kJ/kg (245 BTU/lb). Dry ice density is usually between 1.2 and 1.6 g/cm³. The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water or ice and leaves no moisture as it changes state.







Uses of dry ice

• Dry ice can be used to flash freeze food. It is used commercially to flash freeze tuna for sushi. It can also be used to flash-freeze laboratory biological samples.
• Dry ice can also be used to cool computers, as an alternative to fan, water, LN2, or phase change cooling.
• Dry ice can also be used for making ice cream.
• It can be used as bait to trap mosquitoes and other insects.
• Dry Ice is also used in cloud seeding: the process of altering cloud precipitation.

Manufactural of dry ice

• Gases containing a high concentration of carbon dioxide are produced. Such gases can be a byproduct of some other process, such as producing ammonia from nitrogen and natural gas, or large-scale fermentation.
• Carbon dioxide-rich gas is pressurized and refrigerated until it changes into its liquid form.
• The pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. The extreme cold makes the liquid solidify into a snow-like consistency.
• The snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.

Food colouring

A food coloring (colouring) is any substance that is added to food or drink to change its color. Food coloring is used both in commercial food production and in domestic cooking.
People associate certain colors with certain flavors, and the color of food can influence the perceived flavor, in anything from candy to wine. For this reason, food manufacturers add dyes to their products. Sometimes the aim is to simulate a color that is perceived by the consumer as natural, such as adding red coloring to glacé cherries.

While most consumers are aware that food with bright or unnatural colors (such as the green ketchup mentioned above or children's cereals such as Froot Loops) likely contain food coloring, far fewer people know that seemingly "natural" foods such as oranges and salmon are sometimes also dyed to mask natural variations in colour. Colour variation in foods throughout the seasons and the effects of processing and storage often make color addition commercially advantageous to maintain the color expected or preferred by the consumer. Some of the primary reasons include:

-Offsetting color loss due to light, air, extremes of temperature, moisture, and storage conditions.
-Masking natural variations in color.
-Enhancing naturally occurring colors.
-Providing identity to foods.
-Protecting flavors and vitamins from damage by light.
-Decorative or artistic purposes such as cake icing.

Though past research showed no correlation between Attention Deficit Hyperactivity Disorder and food dyes, new studies now point to synthetic preservatives and artificial coloring agents as aggravating ADD & ADHD symptoms, both in those affected by these disorders and in the general population. Older studies were inconclusive quite possibly due to inadequate clinical methods of measuring offending behavior. Parental reports were more accurate indicators of the presence of additives than clinical tests. Several major studies show academic performance increased and disciplinary problems decreased in large non-ADD student populations when artificial ingredients, including artificial colors, were eliminated from school food programs.
Norway banned all products containing coal tar and coal tar derivatives in 1978. New legislation lifted this ban in 2001 after EU regulations. As such, many FD&C approved colorings have been banned.

-Tartrazine causes hives in less than 0.01% of those exposed to it
-Erythrosine is linked to thyroid tumors in rats.
-Cochineal, also known as carmine, is derived from insects and therefore is neither vegan nor vegetarian. It has also been known to cause severe, even life-threatening, allergic reactions in rare cases.

Tooth bleaching

Dental bleaching, also known as tooth whitening, is a common procedure in general dentistry but most especially in the field of cosmetic dentistry. A child's deciduous teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker due to changes in the mineral structure of the tooth, as the enamel becomes less porous.Whitening is performed by applying a high concentration of oxidizing agent to the teeth with thin plastic trays for a short period of time, which produces quick results. The application trays ideally should be well-fitted to retain the bleaching gel, ensuring even and full tooth exposure to the gel. The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide, or hydrogen peroxide itself. The bleaching gel typically contains between 10-30% carbamide peroxide (15% is recommended) which is roughly equivalent to 3-10% hydrogen peroxide concentration.

Side effect of teeth bleaching

The side effects that occur most often are a temporary increase in tooth sensitivity and mild irritation of the soft tissues of the mouth, particularly the gums. Tooth sensitivity often occurs during early stages of the bleaching treatment. Tissue irritation most commonly results from an ill-fitting mouthpiece tray rather than the tooth-bleaching agent. Both of these conditions usually are temporary and disappear within 1 to 3 days of stopping or completing treatment.

People who are sensitive to hydrogen peroxide (the whitening agent) should not try a bleaching product without first consulting a dentist. Also, prolonged exposure to bleaching agents may damage tooth enamel. This is especially the case with home remedy whitening products that contain fruit acids.

Bleaching is not recommended in children under the age of 16. This is because the pulp chamber, or nerve of the tooth, is enlarged until this age. Tooth whitening under this condition could irritate the pulp or cause it to become sensitive. Tooth whitening is also not recommended in pregnant or lactating women.

Quartz

Quartz is the second most abundant mineral in the Earth's contnental crust. It is made up of a continuous framework of SiO4 silicon-oxygen tetrahedral, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. The Silicate class is the largest and most interesting class of all the classes. It is devided into groups based on mineral structures: Nesosilicates (single tetrahedrons), Sorosilicates (double tetrahedrons) , Inosilicates (single and double chains), Cyclosilicates (rings), Phyllosilicates (sheets), Tectosilicates (frameworks.) Quartz is a Tectosilicate. Then there are the members of the tectosilicate subclass: The Feldspar Group, The Feldspathoid Group, The Quartz Group, and The Zeolite Group. As you might assume quartz is part of the Quartz Group. All of the minerals in this group are made of SiO2. They do not all share the same properties but are still made of the same thing.

Quartz forms unusual crystals. They form as hexagonal prisms with their base pyramids modified by rhombohedral faces. This makes it Trigonal. The crystals are commonly large, single, and faultless. They are usually prismatic. These crystals may also be in disorganized groups. Crystals frequently twin; a famous twinning habit is the Japanese twin, where two crystals contact at a 90?angle. Quartz crystals can also contain certain "growths". One is a scepter growth, where the top of a crystal bulges out from the rest of the crystal, and another is a phantom growth, where one crystal forms over another, leaving a ghosted form inside.

Besides the industrial uses quartz can be used as jewelry and other gem uses. Crystalline quartz is the most common type of quartz. However, well-developed clear crystals are rare. Clear quartz crystals are called rock crystals. When they are cut as gemstones, they may sparkle as brightly as diamonds.

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