This chem talk talks about how electrolytes are substances that dissolve in water that make solutions to conduct electricity. We were able to use a conductivity tester to figure out if the solution conducted electricity. In order to conduct electricity a solution must have charged particles that can move. Every solution that was tested in the lab were dissolved in water with the substances that broke not charged particles being the only electrolytes. In order to have a solution that conducts electricity charged particles must be present and the charged particles have to be able to move around. When compounds dissolve in water to form charged particles it is known as ions. This compounds are commonly formed by a positively charged metal ion and a negatively charged ion to balance the charge. An example of this is regular table salt., as sodium chloride (NaCi), is made of sodium ions (Na+) that has charges of +1 and chloride ions (CI-) that contains charges of -1. When a few Na CI crystals dissolve in water, sodium ions and chloride ions will separate from the crystal and get surrounded by water molecules. Considering that the ions are surrounded by water, they are able to move about in the water. In addition to this charged particles can move, which means that a solution of sodium chloride can conduct electricity. Molecular compounds are unable to crumble into ions when they dissolve. This can be seen in sugar as sugar molecules when it dissolves. Molecules do not form charged particles in solution meaning that solutions made of molecules dissolved in water do not conduct electricity. Molecules unable to create ions in a solution are simply called non-electrolytes. A battery is considered an electrochemical cell; this means that it is formed with two half cells. One side of this cell is where oxidation occurs, this is known as the anode. On the other cell reduction occurs, this is called cathode. The only purpose of referring to the term half-cell is because they can’t exist without the other one. This means that in order for a reduction to happen oxidation has to happen and vice versa. In this lab zinc metal oxidized. When the battery is going the zin is going through a reaction. Zinc ions and electrons get produced at the anode. The zinc ions will enter the zinc nitrate solution, as the electrons go through the wire. As a result, the electrons reach the copper metal electrode where reduction will occur. In this side of the reaction the copper ions from the solution will combine with other electrons to form neutral copper metal atoms. The copper metal electrode’s mass will increase considering that the copper metal is slowly attaching to it. The blue color from the copper nitrate solution will decrease because of the copper ions being used up. The copper ions will also come from the NO3- ions that will join in the solution after being pushed through the salt bridge. The electricity can only travel spontaneously in one direction in a battery. This is because of the activates of the two metal electrodes used in the half- reactions that came from converting the Zn metal atoms to Zn2+ ions in one of the cells, and from the Cu2+ ions to Cu metal atoms in the other cell. Zinc metal is more reactive than copper metal. This means that Zn will react unpredictably with Cu2+ and Cu will not react spontaneously with Zn2+. In addition to this the farther apart the two metals are from each other the more powerful the metal/ other metal ion reaction will be.
I was excited to read this chem talk to figure out what occurred in this lab. I was intrigued by the chem talk and finding out about how the zinc and copper reacted in the la. It was interesting to hear about how electricity affected the oxidation and reduction process of the two metals.
This chem talk talks about how metals are shiny. It tells us that there are other important properties as well such as that they can conduct electricity. They conduct hear, making them useful in cookware. Considering that most metals can withstand high temperatures they are used to build strong structures. They can also be pounded into different shapes with a hammer to make them into nails, flat surfaces, or boxes. We can see that most of the elements in the periodic table are metals. Most of the metal elements don’t appear commonly as pure metals in nature. Most of these metals will be reactive with hydrogen, and are usually discovered in their ionic forms, as positively charged ions involved in solid crystals or dissolved in water. Activates of metals have been studied for hundreds of years. A large portion of chemistry originated from alchemy, which was common in medieval times. The alchemist was supposed to create gold out of other metals. You are unable to do this chemically due to the identity of an atom being specified by how many protons are in its nucleus. If atoms interact then their order of electrons will change but that is it. This experimenting did reveal certain metals react better with most metal ion solutions than other metals do. Through this they developed an activity series that was comprised of their observations. Since the alchemists made their discoveries, chemists have measured these more accurately. The reaction that is possible between neutral metal atoms is called oxidation- reduction reactions. Oxidation is giving up electrons. Reduction is receiving electrons. As we found out through the investigation if oxidation occurs, reduction also has to occur. Considering that electrons that get given also have to be received oxidation and reduction are sometimes called half- reactions since you need them both to create a reaction. You are able to use half- reactions to balance redox equations by ensuring that the number of electrons lost is the same as the amount gained. When the same number of electrons are lost as are gained, the half- reaction can be added. This will cancel the electrons. We learned that you can write the equation in two directions and that you can test both equations. We also found that the only occur naturally in one direction. The activity series can be used to predict which equations represents a reaction that will occur. From this activity series you are able to see that zinc is a more reactive metal than copper. That means that copper is less likely to react than zinc. While most metals are solid, shiny, ductile, malleable, and conductive of heat and electricity hydrogen takes on the positive nature of a metal.
I found this chem talk fascinating. I wanted to know about what happened in the lab so I looked forward to reading this chem talk it was particularly interesting learning about the history behind people experimenting with metals.
This chem talk mentions how a mole is a counting word that is used to count very large quantities of very small objects (primarily atoms and molecules). 1 mol= 6.022 * . One mole of any singe kind of atom or molecule has a mass equal to its atomic or molecular mass expressed in grams. This is known as the molar mass of the atoms. To find the mass of a compound, the masses in grams of each atom in the compound are added together. One mole of close to any gas at standard temperature and pressure (STP) will occupy the same volume (22.4 L) Standard pressure (1 atm or 760 mm Hg) is near the pressure that you live. When the temperature of a gas increases, the volume occupied by the gas increases. This means that one mole of a gas at standard occupations will occupy 22.4 L, one mole of gas at room temperature will be a bit larger. This lab we calculated the volume of carbon gas needed to inflate a balloon. We were also able to calculate the amount of moles of the reactants needed. This method of figuring these factors out is known as stoichiometry. The most important part of a stoichiometric calculation includes calculating the number of moles of one of the other chemicals in the balanced chemical equation. The coefficients in the balanced equation set the proportions. The proportions will relate to the number of molecules of any reactant or product. If you use three times as much of a starting material that will make three times as much product. Since you can’t measure moles you have to convert it into something that you can measure. Rwo measurements that are used are mass of a solid or a liquid and the volume of the gas. You are able to use the stoichiometry method to convey the mass of a chemical into moles, then you can convert your answer from moles back into grams. You can use the molar mass of a substance. You could also use the coefficients from a balanced chemical equation. Finally, you can use the volume that one mole of gas takes up. Dimensional analysis is used in all of the equations which is when the units multiply and divide in order to give you proper units for the answer. A percent yield is usually lost in the final product is when less than 100 percent of the expected product is found. Percent yield has two purposes which is for scientists attempting to reproduce the original work will know how much product they can expect to recover. If a company needs 100 kg of a certain product, but only expect a 50 percent yield from the reaction they will know to use twice the mass of the reactants to obtain 100 kg of the product. Chemical changes will produce new substances with new properties. Knowing what new substances and new properties will be produced allows chemists to produce remarkable results: this could include new chemicals that can cure diseases, withstand the most difficult conditions, explode or react with other chemicals, or help you do things that couldn’t be done before. In order to control the results of the new chemicals stoichiometry is used.
I found this chem talk fascinating. It was cool to learn about the calculations and get a better idea of what was supposed to be done in class. I wasn’t optimistic about this chem talk because of the lab but I ended up enjoying it.
In this lab we created CO2 gas and then used that to blow up a balloon which would move a lever. We used different materials which would generate a different amount of gas in separate amount of times. Chemists also look at the reactions of the chemicals by the materials in energy, and entropy. This chem talk tells us that matter undergoes a change there is usually a change in their energy. This change involves energy moving from a stored state to a different form. This will not change the total amount of energy in the universe or molecule. If the matter gains energy the energy must be given from somewhere. We can tell whether energy is entering or exiting matter by heat energy. When hear energy enters the matter than the chemicals gain energy. When heat energy is released the matter will lose energy. To help us understand these reactions when talking about energy we can see the water experiment. When the ice cubes were heated the ice would melt which is similar to it gaining more energy. It will gain more energy as the heat is put onto the ice and it is turned to a vapor. While changing the vapor to ice can be thought of as removing energy. When heat energy is added particles will add energy. This new energy often goes to making the particles move faster. This extra energy could end up changing the bonds that exist between the atoms or molecules. Bonds exist within molecules. These bonds take heat energy to break bonds between ions in materials such as the ones that were used in method three. Attractive forces will exist between molecules in solids and liquids. These attractive forces will hold the molecules if solids and liquids together which will prevent them from separating to form a gas. It will take energy to break weak intermolecular forces or chemical bonds. Chemical bonds are stronger and will require more energy. In chemical reactions bonds are broken to form new and different molecules. A positive energy change is called an endothermic change, because heat energy goes into the chemicals. A negative change where the energy is decreased through a chemical reaction is called an exothermic. Most changes will also deal with the structure of the particles in the matter changing. The reactions created in the lab created disorder because CO2’s particles are spread out or have high disorder. Spread or disorder is called entropy. Entropy is shown with the symbol S.
I found this chem talk very interesting and I liked reading the part about the disorder of the particles. My favorite part of the chem talk was finding out in detail about the chemistry behind the lab.
This chem talk explained the early use of dyes and the chemicals behind them. It says that early coloring devices were just from rocks and salts. Dyes are usually defined as organic molecules that bond directly to a textile to produce a color. Considering that they are tightly bonded to the material when they are washed unlike other coloring devices. Dyes have been in human activity since the art of weaving was invented. Egyptian tombs contained dyed materials. There was even Chinese dye workshops around 3000 BCE. Dyes in the past were made from animal, vegetable, and mineral materials. This was due to the raw materials being varied resulting in often unpredictable results. A very famous dye was Tyrian purple. Tyrian purple was extracted from the shells of the marine mollusk Murex Brandaris. The mollusks would have to be crushed and burned in seawater for 10 days to create the dye. Then the material had to be put into the mollusks and sea water and then exposed to sunlight. Despite all the hassle this purple created a beautiful purple color. This led to only the ruling class having the ability to get materials with the rare dye. People such as Julius Caesar and Cleopatra were people who wore clothes dyed with the expensive dye. Chromophore is what gives the dye molecule the color that you see. Groups of atoms within an organic molecule will absorb only certain colors of visible light. White light is all of the colors of the spectrum. The Tyrian purple molecule will absorb red, green, yellow and blue light from ordinary light. The other colors from the spectrum will be reflected resulting in the object to appear purple. In some cases, an auxochrome will be in the molecule which will change the chromophore’s ability to absorb light energy. A dye must also have the ability to be water soluble so that it can interact with the textile to be colored. Once the dye has gone through the fabric, the mordant helps the process in the binding of the dye to the textile. One problem that occurred from natural dyes is that they usually fade when they are repeatedly washed or when they get large exposures to light. We know that certain metallic salts were added to wool, making the dyeing becoming less likely to wash out. These metallic salts were known as mordant. These were thought to have helped the wool in the material to soak into the wool and keep the dye in the material after being washed. Aluminum ion, chromium ion, copper ion, iron ion, and tin ion were usually used as a mordant. Wool is usually pre-treated with a solution of the metal salt to make sure that the metal ions attached themselves to the wool; before dyeing. When the dye is introduced to the solution the, it will form an insoluble complex salt, which is called a lake, With the metal ions within the fiber. The resulting large, complex molecule will be less water soluble than the individual dye molecules. This means that the dyed material is less likely to lose its color when it is washed. A mordant can be used to increase the range of colors that will be available from a given dye. Early dyes were primarily made from natural resources while close to all current dyes are produced synthetically. Synthetic dyes will give a wide range of color and reproducibility that wouldn’t be found in dyes that are based from natural resources. The most recent section of the twentieth century has shown increased interest in natural dyes. This is due to the unpredictability of the dyes from the natural resources and how they create a “one-of-a-kind” color.
This chem talk was extremely interesting. It was particularly interesting to learn about the evolution of dyes and how it began to shift from dyes made from natural resources to synthetic dyes. While I wasn’t particularly excited to read this chem talk I found myself enjoying reading it.
This chem talk was about how the we saw in this lab was insoluble compounds. These compounds are used as pigments for paints. This pigment is crushed and mixed with a liquid which is called the binder. The liquid could be water or another liquid such as linseed oil, turpentine, or guar gum. When the pigment is insoluble in the liquid, it becomes a suspension of particles in the liquid. This ends up with the pigment particles being left behind when the paint dries. Most reactions occur in water. When you combine certain cations and anions, water- insoluble ionic compounds have a possibility of forming. (cations are positively charged ions and anions are negatively charged ions.) When the ions are in separate aqueous solutions and then put together, an insoluble solid, or precipitate forms will take shape. The precipitate is an ionic compound often considered salt. It forms when certain ions attract each other so strongly that they are removed from the water solution and are the end product of a chemical reaction. A double- replacement reaction is a type of precipitation reaction where a precipitate forms when one of the products is insoluble. In the reaction between solutions of zinc nitrate and sodium carbonate the zinc ions and the carbonate ions will form a solid that no longer stays in a solution because they are so strongly attracted to each other. Ions that are not affected in the reaction are called spectator ions. When these ions are removed from the equation it is called the net ionic equation. This makes it possible to tell whether or not a precipitate will form in a double- replacement reaction. There are rules that chemists refer to but don’t memorize that are 1. Most nitrate, acetate, and perchlorate compounds are soluble. 2. Metals in Group 1A and ammonium compounds are soluble. 3. Most chloride, bromide, and iodide compounds are soluble. With exceptions Cu+, Ag+, Pb2+, Hg2+. 4. Most sulfate compounds are soluble, except when they are combined with Ba2+, Sr2+, and pb2+ `. Ca2+. 5. Carbonate and phosphate compounds are only slightly soluble. 6. Most hydroxide compounds are insoluble except, when combined with group 1A cations. Ca(OH)2 is slightly soluble. An ionic compound is considered soluble if a large amount of it dissolves in water.
I found this chem talk very interesting. The part about how the double- replacement reaction was particularly interesting. It was entertaining to learn about the chemistry behind the reactions in water that can be used to form paint and pigments.
This chem talk was about metals keep their composure through metallic bonds. Metallic bonds are formed through the sharing of valence electrons among all the atoms in a metal. The nature of a metallic bond can be seen through an electron- sea model. Outer electrons in metallic bonds are constantly moving around the cations which are positively charged metal ions. These electrons don’t go with one cation but instead move around as part of the whole metal crystal. The negatively charged electrons will move around in a form similar to a sea resulting in the effect of holding positively charged metal ions in a loosely fixed position. Metals are crystalline just like diamonds or salts. While they are crystalline they won’t cut or shear of along an edge. Metals will have a crystal structure with many valence electrons surrounding metal cations. Electrons that are on the cations and anions in salt compounds will be localized. Considering that most electrons are free to move about, most of the atoms in metals can move past each other when you hammer them. This is known as malleability. The more malleable a metal will be the easier, the weaker it will make the object. An alloy is when other elements are introduced into an iron metal. An alloy is classified as a substance that has the properties of a metal, but will consist of two or more metals. When you introduce other metals the properties of the primary metal are changed. One of the earliest metals that humans were using was bronze, bronze is a mixture between copper and tin. Another important alloy that humans made was brass which was made out of copper and zinc. Both of these alloys were more durable than copper, which helped to make better tools. As time progressed more alloys were formed using iron which had a big impact on warfare, agriculture, and art. In this lab we used three processes to change the properties of steel. When using these processes, we were able to alter the arrangement of iron atoms while carbon atoms were introduced into the crystal structure. While the iron slowly cooled the crystalline structure would rearrange with the excess carbon being pushed out. The annealed steel would contain fewer carbon atoms between the iron items resulting in a softer, more malleable and more pliable steel. If the steel becomes cooled quickly after being heated to a red hot, then the carbon atoms will become locked into the crystalline structure. Since carbon atoms have a tendency to hold onto electrons, this makes it more difficult for the iron atoms to slide past each other. This results in a hardened steel that is hard and brittle. If this hardened steel is gently heated, the crystalline structure will change again, this results in some of the bonds between the carbon atoms and electrons being relieved. This will give you a tempered steel that will have properties of both annealed and hardened steels. This means that it will be hard, malleable, and useful for tools and building materials. Pure gold is a deep-yellow color, soft, and very malleable. Since pure gold is so soft, the gold that is used in jewelry and artwork is made of gold- silver- copper alloys that will increase its strength. Most gold jewelry will be 18- karat, 16- karat, or 14- karat as a result. The color of gold jewelry from yellow to pink will be determined by the metals that were added to increase its strength. The malleability of gold is essential in art. A gold leaf has a range of thickness of 0.1 to 0.3 um which is a millionths of a meter. Brass alloys may contain traces of other elements but are primarily copper and zinc. Aluminum, iron, and manganese are added to brass to improve its strength while adding silicon will improve its resistance to wear. Bronze will contain mostly copper and tin but sometimes contains a little bit of other elements such as zinc or phosphorus. It a better alloy than bronze because it is stronger, harder, and more durable than brass. Bronze is used as the base for many sculptures. Bronze also has properties that are essential for bells and gongs. Bronze alloys will vary in color from a silvery hue to a rich, coppery red. The United states has a standard for bronze which is that it must be 90% copper, 7% tin, 3% zinc. While alloys such as bronze have been used for decades, the art world has used exciting types of alloys called shape- memory alloys or SMAs. These are sometimes called “smart material” because they have the ability to be bent at a lower temperature and then have the ability to revert back to their original shape once they are heated. This is caused by a reversion to the original crystal structure at their transform temperature. The most commonly used SMAs include NiTi (nickel- titanium), CuZnAINi (copper- zinc- aluminum- nickel), and CuAINi (copper aluminum- nickel).
I found this chem talk extremely fascinating. It was interesting to learn about all of the different alloys that exist out in the world and the purposes of the alloys.
This chem talk was about how in the lab we observed different acid and base solutions. We were able to tell the difference in the solutions because of an indicator. This indicator is called an acid base indicator and is a substance that will change color when it is exposed to either an acid or a base. We could have used red and blue litmus paper before this. When a base is used on red litmus paper it will turn it blue. When acid is used on a blue litmus paper it will turn it red. This chem talk also says that we used a universal indicator in this lab. A universal indicator is a mixture of acid- base indicators that tells you how acidic or basic a solution is and is a mixture of acid- base indicators. Common acids are battery acid which is sulfuric acid or vinegar which is acetic acid. Acids usually have a sour taste, neutralize bases, react with most metals and react with certain indicators to produce a color change. Common bases that you might know include ammonia (ammonium hydroxide) and antacids (magnesium hydroxide). Bases will have a bitter taste and a slippery feel, are corrosive, neutralize acids, and cause certain indicators to produce a color change. The Ph in a solution is used to measure the concentration of hydrogen ions (H+) in that solution. (An ion is an atom that has gained or lost an electron.) A high concentration of H+ ions (an acidic solution) is indicated by a low pH. When the pH of a solution is less than 7, the solution is acidic. If the pH of a solution is greater than 7, the solution is basic. Strong acids will dissociate to create many hydrogen ions om a water solution, while weak acids dissociate to produce only a few H+ ion in water with their solutions having a higher pH. All acids will produce H+ ions in a water solution. Carbonic acid is a weak acid that will form both hydrogen ions and carbonate ions (HCO3-). There will be a change in pH which will be because of the formation of carbonic acid and the H+ ions into the water. Since your breath and the atmosphere both naturally contain CO2, all rain will be slightly acidic. When the amounts of H+ and OH- are the same, the solution is neutral with the pH as seven. H+ is a proton. Hydrogen has one proton and one electron. If the electron gets removed, then it becomes identical to a single proton but with a different name. One water molecule in every 10 million dissociates and becomes an H+ ion and an OH- ion. This happens when one H in the H2H loses an electron and the OH in H2O gains an electron. In a water solution, the H+ is an isolated proton is never found, leading to it attaching to a molecule of water. The H+ attaches to the H2O and becomes H3O. H3O is known as the hydronium ion. Arrhenius’s definition of acid can be summarized as releases H+ in water solution and his definition of Base is releases OH- in water solution. Bronsted and Lowry’s acid definition is that Acid is H+ donor and the Base is the H+ acceptor. Lewis’s definition of acid was that it is the electron pair acceptor and the base is the electron- pair donor. The gas SO2 is released into the atmosphere when coal and petroleum products are burned. Another source of atmospheric SO2 is volcanic eruptions. Sulfur dioxide can react with water to produce sulfurous in the atmosphere. Sulfuric acid and sulfurous acid will form hydronium ions in water. When water has a pH lower than 5.6 it is considered to be acidic. Acid deposition which can come in the form of acid rain can damage buildings, statues and make lakes and streams unsuitable for life. The CaSO4 (calcium sulfate) is soluble in water and when removed from marble, it will cause it to deteriorate. Sandstone and granite are mainly made of oxides of silicon. Making these materials not react readily with acid. Metals may be placed outdoors but zinc sulfate is soluble in water which will cause anything outside that is made of zinc to deteriorate.
I found this chem talk very fascinating. I learned a lot about what occurred in the lab today and about the chemistry behind it. I found the part about the different theories that arose about what an acid and a base where over time particularly interesting.
The chem talk was about how Aristotle did not believe it was possible to have empty space. However, a Greek called Democritus believed that matter was made up of tiny particles that could not be broken down further. By turn of the nineteenth century, Chemists had begun to combine elements to form new substances. This substance was called a compound. Chemists during this time were also interested in measuring the amount of elements used and substances formed. They first attempts at determining masses were wrong probably in part because of the equipment that they had at that time. Chemists noting during the nineteenth century noted that eight parts of oxygen always reacted with one part of hydrogen ending up with nine parts of water. This is an example of the law of definite proportions. Joseph Proust, a French chemist stated this law in 1799. The law was that whenever wo elements combine to form a compound they do so proportionally. Proust observed that 100 g of copper dissolved n nitric acid and precipitated by carbonates of soda or potash, resulted in 180 g of green carbonate. This law does not give direct proof of the existence of atoms. John Dalton, an English scientist, developed his atomic theory in the early 1800s. his theory was based on both the Greek concept of atoms and Joseph Proust studies. Daltons atomic theory contained a series of hypotheses. These were built on data of his time and his observations. These hypotheses were that Matter consists of small particles called atoms. All atoms of on particular elements are identical and their properties are identical. Atoms are indestructible. In chemical reactions, the atoms rearrange or combine, but they are not destroyed. Atoms of different elements have different properties. When atoms of different elements combine to form compounds, they combine in a ration of whole numbers. Dalton’s hypotheses or postulates support the law of conservation of mass, which states that atoms cannot be destroyed, but they can be rearranged and combined with other atoms to form compounds. This means that the mass of the compound must be the sum of the atoms of the compound. This law is still in place today and still valid for chemical reactions but not for nuclear reactions. Dalton’s work advanced the belief in the existence of atoms. Chemists eventually created a scale of relative masses of atoms, this was done through the organized study of chemical reactions. They measured the masses of two elements reacting with each other, as we did in the investigation. They could use this to find out that one elements have twice the mass of a second element. It was discovered that atoms of carbon had a mass 12 times greater than the mass of hydrogen atoms.
I found this chem talk interesting. I found the part about the evolution of chemistry ideas throughout time especially interesting.
Chemistry is used to explain nanosomic events by an understanding of macroscopic phenomena. Chemists rationalize the world by explaining things that cannot be seen. We found gas in this investigation. The gas that we found in this lab was ethylene which is what ripens fruits. Plants release ethylene gas (C2H4) when they age. Ethylene gas is used as a hormone in plants and begins the ripening process of the plants. You can ripen unripening fruit by inserting ethane gas into it. Absorbing the gas from fruit storage areas can stop the ripening process. In this investigation we showed how ethylene gas works on the skin of the fruit. Ethylene gas is in a rare category because it is known as an organic material which means that it is based on carbon molecules. Anything that isn’t organic is inorganic. In the nineteenth century compounds were classified under two categories, organic which meant that they came from living organisms or inorganic which meant that they were obtained from mineral sources. A theory known as vitalism was stated which was that a “vital force” was required to make organic compounds. This theory was disapproved when Friedrich Wohler created an organic in 1828. Organic chemistry is now referred to as the study of carbon compounds. This is the largest area being researched in Chemistry. You can see it in animals and plants every day because plants and animals produce millions of carbon compounds. A large portion of manufactured chemicals are facsimiles of those natural products. Chemists also created a process that will synthesize similar, new chemicals that can be used in society and technology today. Examples of these synthesized chemicals are gasoline, artificial sweeteners and flavors, and multiple medicines. Organic is usually thought of as a natural or not human-made. Organic farms will not use synthetic pesticides or fertilizers. Chemists don’t use organic in this way. You would consider a molecule organic if it came from either a test tube or tomato plant. Chemists would argue that apples are always organic even if they have been cultivated in a manner that is usually not considered organic. Ethylene is part of a group of organic compounds called hydrocarbons. A hydrocarbon is a compound that is made of only carbon and hydrogens. Most fuels are hydrocarbons too. Combustion is when a hydrocarbon burns when faced with oxygen. In a combustion the material is combined with oxygen, heat, and in some cases light. Propane gas is C3H8(g) + O2(g) which will turn into CO2(g) + H2O(g). When you look at the chemical equation you notice that there is a different number of atoms on the both sides of the equation. On one side you have 3 carbon atoms, 8 hydrogen atoms, and 2 oxygen atoms. On the other side you have 1 carbon atom, 2 hydrogen atoms, and 3 oxygen atoms. This violates the law of conservation of mass which says that the total mass of the products of a chemical reaction is the same as the total mass of the reactants. The total mass of the atoms involved is not equal. You fix this by balancing out the equation. Atoms get rearranged during a chemical reaction. This is what occurs in chemical change. It is required though that both sides have the same number and type of atoms. The equation can be balanced by adding coefficients in front of the molecular formulas of the reactants and products. You must change the coefficients but not the molecular formulas. If you changed the molecular formula, you would be changing what chemical reaction you were working with. In this case if you placed a 3 in front of the CO2 product, you would now have three carbon atoms on both sides of the equation. Placing a 4 in front of the H2O product brings the total number of H atoms on both side to 8. This will make a total number of 10 oxygen atoms of the right side of the equation. But if you place a 5 in front of the O2 reactant, that will make the total number of O atoms on both sides equal. You now have an equation seen as C3H8(g) + 5O2(g) and 3CO2(g) + 4H2O(g). This tells you that one molecule of propane reacts with 5 molecules of oxygen to yield 3 molecules of carbon dioxide and 4 molecules of water.
This chem talk was very helpful for helping to clarify what happened in the lab, and gave me a full understanding of what happened in the lab. The clarified why the things that happened in the lab happened on a molecular level. I found this lab particular fascinating and was delighted to read it. I found the section about balancing out the chemical reactions intriguing.