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The Chemistry of Fireworks

The Chemistry of Fireworks

The colours in fireworks stem from a wide variety of metal compounds – particularly metal salts. ‘Salt’ as a word conjures up images of the normal table salt you probably use every day; whilst this is one type of salt (sodium chloride), in chemistry ‘salt’ refers to any compound that contains metal and non-metal atoms ionically bonded together. So, how do these compounds give the huge range of colours, and what else is needed to produce fireworks?

The most important component of a firework is, of course, the gunpowder, or ‘black powder’ as it is also known. It was discovered by chance by Chinese alchemists, who were in actuality more concerned with discovering the elixir of life than blowing things up; they found that a combination of honey, sulfur and saltpetre (potassium nitrate) would suddenly erupt into flame upon heating.

The combination of sulfur and potassium nitrate was later joined by charcoal in the place of honey – the sulfur and charcoal act as fuels in the reaction, whilst the potassium nitrate works as an oxidising agent. Modern black powder has a saltpetre to charcoal to sulfur weight ratio of 75:15:10; this ratio has remained unchanged since around 1781.

The combustion of black powder doesn’t take place as a single reaction and so the products can be rather complicated. The closest thing to a representative equation for the process is shown below, with charcoal referred to by its empirical formula:

6 KNO₃ + C₇H₄O + 2 S → K₂CO₃ + K₂SO₄ + K₂S + 4 CO₂ + 2 CO + 2 H₂O + 3 N₂

Variation in pellet size of the gunpowder and the amount of moisture can be used to significantly increase the burning time for the purposes of pyrotechnics.

As well as gunpowder, fireworks will contain a ‘binder’ – used to hold the components together, and also to reduce the sensitivity to both shock and impact. Generally they will take the form of an organic compound, often dextrin, which can then act as a fuel after ignition. An oxidising agent is also necessary to produce the oxygen required to burn the mixture; these are usually nitrate, chlorates, or perchlorates.

The ‘stars’ contained within the rocket body contain the metal powders or salts that give the firework its colour. They will often be coated in gunpowder to aid in ignition. The heat given off by the combustion reaction causes electrons in the metal atoms to be excited to higher energy levels. These excited states are unstable, so the electron quickly returns to its original energy (or ground state), emitting excess energy as light. Different metals will have a different energy gap between their ground and excited states, leading to the emission of different colours. This is the exact same reason that different metals give different flame tests, allowing us to distinguish between them. The colours emitted by different metals are shown in the graphic at the top of the page.

It’s the metal atom present in the compound that’s important, then – but some compounds are better than others. Hygroscopic compounds (those that attract and hold water) aren’t much use in fireworks, as they can render the mixture damp and hard to burn. Some colours are also notoriously hard to produce. The copper containing compounds tend to be unstable at higher temperatures, and if it reaches these temperatures, it breaks apart, preventing the blue colouration from being exhibited. For this reason, it’s often said that you can judge the quality of a fireworks display on the quality of the blue fireworks! Purple is also quite hard to produce, as it involves the use of blue-causing compounds in combination with red-causing ones.

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10 Chemical Change Examples

 

 

 

Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible. In contrast, physical changes do not form new products and are reversible.Thi is a list of more than 10 examples of chemical changes.

                              

      1.    RUSTING OF IRON

2.    COMBUSTION (BURNING) OF WOOD

3.    METABOLISM OF FOOD IN THE BODY

4.    MIXING AN ACID AND A BASE, SUCH AS HYDROCHLORIC ACID (HCL) AND SODIUM HYDROXIDE (NAOH)

5.    COOKING AN EGG

6.    DIGESTING SUGAR WITH THE AMYLASE IN SALIVA

7.    MIXING BAKING SODA AND VINEGAR TO PRODUCE CARBON DIOXIDE GAS

8.    BAKING A CAKE

9.    ELECTROPLATING A METAL

10. USING A CHEMICAL BATTERY

11. EXPLOSION OF FIREWORKS

12. ROTTING BANANAS

13. GRILLING A HAMBURGER

14. MILK GOING SOUR

 

 

 

 

 

 

 

                                                                                         

Chemestry in daily life

ABC of chemistry 🤓

Test Yourself Here on the Hardest VCE Chemistry Questions Ever Asked

Quiz

Colourful Chemistry: Chemistry of UNIVERSAL INDICATOR

By definition, an indicator is a substance that changes colour in different pH environments. Universal indicator is a brown-coloured solution—containing a mixture of indicators—that can be added to any substance to determine its pH. Like all indicators, universal indicator changes colour in different pH environments. At low pH, it appears red, and at high pH, it appears blue or violet. At neutral pH, it appears green. Universal indicator can form a continuous spectrum of colours that give an approximate reading of the concentration of protons in a sample.

Water and propan-1-ol are used as solvents. They are both polar and dissolve all the other ingredients in the solution. Sodium hydroxide (NaOH) is an alkaline solution that adjusts the pH of the universal indicator to ensure that each colour is shown at the correct pH value. It is necessary to add NaOH to the universal indicator because some of the indicator compounds (e.g. methyl red) are acidic themselves, which would affect the colour of the other indicators present. NaOH is added to neutralise the solution.

Methyl red is red at pH <5 and yellow at pH >5. It provides orange and red hues to the universal indicator solution at low pH. The end point of an indicator compound is defined as the pH at which it changes colour. The end point of methyl red, therefore, is somewhere around pH 5.

Bromothymol blue is blue at pH >6 and yellow at pH <6. It gives blue and indigo hues at high pH. Its end point is therefore around pH 6.

Thymol blue has two end points: it is red below pH <2, blue at pH >8 and yellow in the middle. Thymol blue allows universal indicator to differentiate low and very low pH by providing another red hue below pH 2. Thymol blue is yellow at pH 7, which, when combined with bromothymol blue (which is blue at pH 7), give a green colour.

       Making     the     Love    Drug   

January 1999, Chemistry in Britain. How do you turn a possible treatment for angina into a world-renowned anti-impotence drug? Elizabeth Palmer looks at the story behind the drug that is commanding international attention On 27 March 1998, the US Food and Drug Administration approved a new drug for treating male erectile dysfunction (MED). Since then the drug has achieved record sales and has been the subject of extraordinary media interest, becoming a household name in the few months that it has been available. The drug is of course Viagra, more scientifically known as sildenafil citrate. But behind all the media hype is a drug with serious potential. MED affects an estimated 10 per cent of men - a figure that leaps to an incredible 52 per cent of men aged 40 to 70 years. Viagra is the first oral anti-impotence drug to offer them hope. The story of viagra's discovery is an interesting one. Viagra started life as a potential treatment for hypertension, and then angina. So how did the Pfizer team who discovered the drug at the company's Sandwich site in Kent, UK, make the sideways step to such a highly successful drug for impotence? The discovery programme began in 1985 when Simon Campbell and David Roberts, both chemists at Pfizer, wrote a proposal to look for antihypertensive and antianginal compounds that would work by inhibiting phosphodiesterase (PDE). This intracellular enzyme hydrolyses cyclic nucleotides such as cyclic guanosine monophosphate (cGMP) - a vasodilator that relaxes the vascular smooth muscle of the blood vessels, allowing increased blood flow. Nick Terrett joined the programme in 1986 as head of the chemistry team. His team - made up of four chemists including himself - was given the task of finding a compound that would inhibit PDE. The team began a typical medicinal chemistry discovery programme to find a chemical starting point that would be potent, selective, novel and ultimately effective. They started by checking the literature to see if there were any compounds that raised levels of cGMP by inhibiting PDE. One of the very few compounds known at that time for inhibiting PDE was Zaprinast (1), which was developed as an antiallergy compound, but hadnever been commercialised by its developers, May and Baker (now part of Rhône-Poulenc Rorer). Zaprinast is a vasodilator in vitro, but it isn't only a PDE inhibitor — it works by a number of different mechanisms. 'There was other pharmacology associated with Zaprinast. It wasn't selective or potent enough, and we wanted a compound that was proprietary to Pfizer', Terrett says. The team needed to find a molecule that would bind to PDE's active site, so that it couldn't convert cGMP to the inactive GMP form. They studied the structure of the substrate cGMP as a starting point, hoping to find some clues as to how they might modify the chemical structure of Zaprinast to make it more selective and potent. By exploring other ring systems, the team found that some had improved activity over Zaprinast, such as the pyrazolopyrimidinones (eg 2). The researchers substituted a propyl group for a methyl group on the pyrazolopyrimidinone system to increase affinity for PDE and give a more potent compound. They then added a sulphonamide group to reduce lipophilicity and increase solubility. The resulting compound was later to become known as Viagra, but in 1989 was known by the team simply as UK 92480 or sildenafil (3). In all, about 1600 compounds were made over the lifetime of the project. 'This was in the days before high throughput screening and combinatorial chemistry. With hindsight we could have made some of the analogues more rapidly using a parallel synthetic technique, but this wasn't commonly practised at the time', Terrett says. It was a high level technical challenge, and according to Gill Samuels, also a member of the Viagra discovery team, 'there was a lot of ground-breaking work to be done because there wasn't a great deal of confidence in the company that we could get a really potent and selective inhibitor'. Pfizer started Phase I clinical trials of sildenafil in healthy volunteers - ie men who had no history of coronary heart disease - in July 1991. The volunteers were given increasing quantities of the drug to see how well they tolerated it and if there were any side effects. The following year, two things happened in parallel, changing the direction in which the discovery team were heading with the drug. Sildenafil had progressed to a limited Phase II trial in patients who had severe coronary heart disease (angina), but it did not fulfil the team's expectations in terms of its activity. However, a further Phase I study was being carried out at the same time, which was intended to push sildenafil to its limits. This was a 10 day multiple high dose study to observe how much of the drug could be given to the volunteers without incurring side effects. Because it was a high dose level, the volunteers did report side effects, including headache, indigestion, visual disturbance, muscle ache - as well as a change in erectile function. A curious side effect... For the discovery team this change in erectile function was an interesting phenomenon; it fitted their data and the literature sufficiently for them to wonder if it could occur at a single dose of 100mg. 'Remember that at this point there was no certainty it could be a useful treatment for erectile dysfunction (ED) because the dose was too high', says Terrett. The team also knew that getting such an effect in normal volunteers didn't necessarily mean that it would happen in men with ED. Because the drug did not look promising for treating patients with coronary disease, the team debated the possibility of using sildenafil as a therapeutic drug for MED. It took much deliberation to come to the decision - there were still many questions to be answered about how sildenafil worked - but eventually the team decided to change direction and put sildenafil on trial as a drug for MED. 'There was no eureka moment', says Terrett. 'It was by no means guaranteed at this point that it would lead to a drug for ED'. But the pieces of the jigsaw were starting to come together. In 1992 Science named nitric oxide (NO) 'Molecule of the year', and researchers were beginning to understand the role of NO as a signalling molecule in the body - a discovery that has been recognised in last year's Nobel prize for medicine (Chem. Br., November 1998, p29). 'There was now a potential mechanism to underwrite what we thought might be happening in the Phase I trials', says Terrett (see Box 1). 'A phenomenon with no mechanism attached makes people feel nervous, particularly when it's to do with something like erectile function'. ...causes excitement In May 1994 Pfizer began the first Phase II trial of sildenafil in men suffering from ED. It was a limited trial using only 12 patients with ED. But 10 out of the 12 patients showed improved erectile function, and according to Terrett 'there was a lot of excitement at that point'. The next step was to take the drug out of the clinic and into the home setting - a more natural environment for assessing the drug - which happened between September 1994 and February 1995. During this outpatient trial the team came up against the problem of how to do a clinical trial for ED in the home; there was no precedent. So they developed the International Index of Erectile Function - a sexual function questionnaire that the patient fills in to give some quantification of the degree of ED and the benefit of taking the drug - which has now become the standard for assessing ED. 'This was critical because it meant we now had the same benchmarks for clinical trials in different countries', says Terrett. There were a lot of changes in direction along the way and an element of uncertainty, similar to most drug development programmes. As Samuels wryly comments, 'People always look back at these programmes and think that every turn we took had a clear signpost on it saying "This way to marvellous efficacy", but in fact there is often a fork in the road. At every fork we came to as we moved forward with Viagra, we probably chose the most challenging route to make sure we got the highest quality answer'.Patients were asked to keep a daily diary and to respond to the questionnaires: there was encouraging feedback (Fig 1). Then it was a case of starting 'open-label' studies where people knew what it was they were taking; 36 centres - usually the urological departments of hospitals - were involved in the UK, France and Sweden, assessing 225 patients over 32 weeks. At the end of the trial 88 per cent of patients reported that sildenafil had improved their erections and just over 90 per cent wanted to continue with the treatment. Of those that withdrew, less than 4 per cent gave lack of efficacy as the reason, and 4 per cent because of adverse effects (headache, indigestion). 'We were finding that we could get efficacy at a single dose and that there was a dose-response effect, and if there's anything that gladdens the heart of a pharmacologist it's getting a dose-response relationship', says Samuels. Viagra has now helped over 3 million people worldwide to overcome impotence, a condition that has a significant impact on the quality of life for many men and their partners. But the Pfizer team are not finished yet. 'Clearly with a drug like Viagra you don't rest on your laurels', says Terrett, adding 'We understand the drug extremely well now and will continue to look for improvements. We have received dozens of letters from men who have been helped by Viagra and this is what makes it all worthwhile'. Box 1. How Viagra works Sexual stimulation leads to the local release of nitric oxide (NO) from nerve endings and endothelial cells in the spongy erectile tissue — the corpus cavernosum — of the penis. NO switches on the enzyme guanylate cyclase, which converts guanosine triphosphate into cyclic guanosine monophosphate (cGMP). This key second messenger is a vasodilator — it relaxes the vascular smooth muscle of the blood vessels of the corpus cavernosum, so that the blood flows more strongly leading to an erection. However, at the same time cGMP is hydrolysed by phosphodiesterase type 5 enzyme (PDE5), to inactive GMP. Men who have erectile dysfunction (ED) are often producing insufficient amounts of NO. So although they are producing a small amount of cGMP, it is being broken down at the same rate. Viagra works by blocking part of the cycle. It selectively inhibits the PDE5, by binding with PDE5's active site. This prevents the hydrolysis of cGMP to inactive GMP, allowing cGMP to accumulate and prolong the vasodilation effect. Because of this mechanism of action, Viagra works regardless of the underlying cause of ED. It is effective in men with ED associated with a variety of medical conditions, including vascular and neural disease, diabetes, prostate surgery, depression and spinal injury (providing sufficient nerve has been left intact). Whatever the cause of reduced NO formation, Viagra still works. However, Viagra is not an aphrodisiac. Because the drug is potentiating the natural effects of cGMP rather than stimulating its production, it only works in response to sexual stimulation. How NO mediates erections At present, 1400kg of highly concentrated pure sidenafil citrate is made each week by an automated process in a factory in Ringsakiddy, Co Cork, Republic of Ireland. Making one batch of the drug takes 21 days. The Scheme below shows the original 'discovery' route used to synthesise sildenafil. Commercial manufacture of the drug is by an alternative route, the details of which are strictly under wraps. The resulting white crystalline powder is taken to one of three centres - in France, Puerto Rico or the US - where it is diluted with inactive ingredients: microcrystalline cellulose, anhydrous dibasic calcium phosphate, croscarmellose sodium, magnesium stearate, hydroxypropyl methylcellulose, titanium dioxide, lactose and triacetin. The powder is then coloured blue, and formulated into the characteristic rounded-diamond-shaped tablets equivalent to 25mg, 50mg and 100mg of sildenafil. Pfizer aims to start producing the drug at its plant in Sandwich, Kent, for sales in Britain in the year 2000.

Further information

• Visit the Pfizer website at www.viagra.com
• Science, 1998, 258, 1861.
• European patent 0463756, 1992.

Aspirin rin rin

A S P I R I N    RIN     RIN  

Aspirin, also known as acetylsalicylic acid (ASA), is a salicylate medication, often used to treat pain, fever, and inflammation. Aspirin also has an antiplatelet effect by stopping the binding together of platelets and preventing a patch over damaged walls of blood vessels.

Thanks aspirin, you're wonderful!

Sometimes it's C H E M I S T R Y

There is another endothermic reaction that what happens to me now ... 

I just want to absorb its heat, view your profile, tell his side every step ... 

this is new to me, that to me is love.

His walk shook my senses, the breadth of his look allotropy created in me, 

which my body had asked, before this, 

my confidence was shattered and my dynamism that melted ice melting.

Two sciences together in search field components, 

one outdoor and one indoor aspects. 

Coincidence or destiny, no matter, I create my own destiny.

And now I felt confidence, he had given me, 

the few words eventually were becoming hours together, 

experiences, theories, laughter, vectors, children fighting, 

trouble, songs, theorems, cheesy letters ...

The chemistry of autumn colors

The variety of colors of autumn trees are related to photosynthesis, ie the process by which the leaf chlorophyll transforms water and carbon dioxide into food. In summer, green plants produce large doses of chlorophyll. But when winter comes and the days get shorter the production of this green substance is reduced. And we began to see other pigments. Carotenoids, for example, necessary to capture sunlight give a yellow to intense sometimes leaves as gold. This anthocyanin only as scarlet oak trees or in some maples, generates tones ranging from red to purple.

The colors of this season are more intense when autumn days are sunny and the nights are cold, but not if the temperature drops below freezing.

 

  How many words you can do with the                        chemical elements?

How do you know?

Ten curious things of daily chemistry.

1. Ethylene is a gas produced by the fruit to mature. The oranges are very sensitive to ethylene and deteriorate soon. 

2. The butyric acid is responsible for the unpleasant smell of rancid butter. 

3. The lipstick is elaborated with bee wax and oil. The oil tends to be castor.

4. The fructose (fruit sugar) is sweeter than sucrose (cane sugar).

5. The juices from the stomach have a pH of 1.6 to 1.8 . Are more acids than lemon juice (2.1 ).

6. Thymol is used in the conservation of books to combat the fungi. Present in nature in the thyme and oregano, two widely used aromatic herbs for cooking.

7. Myoglobin is the pigment responsible for the color of the red meat. The meat of an animal more old will be darker.

8. The miristicina is a toxic alkaloid present in the nutmeg that can cause hallucinations.

9. The geraniol is a natural alcohol present in fragrant flowers such as roses and geraniums. Bees use it to mark the flowers with nectar.

10. Tungsten is used as filament in the bulb. Its name derives from the Swedish tung sten, which means "heavy stone". In regard to the neon tubes, the name of this element began to be used in New York and means "new".