Signs of chemical reactions
Reactions that utilise chemicals involve the transformation of materials that are chemical in nature. The chemical substances that participate in these interactions are known as reactants while those substances generated are identified as the products. The process of transforming the reactants to products can lead to molecules integrated to one another to form bigger ones or molecules disintegrating to result to two or smaller ones (Bateman 12). A chemical change cannot be reversed.
The reactions involving chemical substances generate one or more products that normally have features different from the reactants and possess diverse physical and chemical properties. Chemical reactions can either be spontaneous, needing no input of energy, or non-spontaneous, and may require some form of energy, either as heat, light or electricity to start the reaction (Bateman 23). These changing of individual reagents into other compounds can be represented by use of equations that denote both the reacting elements and the resulting outcomes. During normal circumstances, the reacting materials are on the left side while the resulting products are usually on the right side of the equation.
There are several aspects that can indicate that a reaction involving chemicals have taken place. The first indicator is the formation of a cloudy solid product that settles in the vessel used to conduct the experiment (Bateman 20). A reaction that results to formation of the ionic solid, which cannot dissolve, occurs when negative ions and positive ions join together in a solution that is aqueous. For example, a solution of Silver Nitrate when taken and poured into a solution of Sodium Chloride, a chemical reaction process takes place forming a white solid of Silver Chloride (Bateman 27).
Likewise, when liquid potassium chromate (K2CrO4) is added to a solution of barium nitrate (Ba[NO3] 2, a solid of barium chromate (BaCrO4) will be formed. This reaction process also generates a solution, but our concern remains that the mixture of two solid substances has led to the generation of a solid in a solution that is different (Johnson et. al. 77). However, several factors have been found to determine the formation of the solid in a reaction process involving chemical such as temperature which may exert some influence as well as the concentration of the solution participating in the reaction process.
Utilizing diverse mechanisms like decanting and filtration can aid in removing the ionic solid from the mixture. The formation of solids in a reaction involving a variety of chemicals has been utilized in finding out if a particular element is present in a solution. Furthermore, it has been used to derive elements for example Magnesium from seawater (Johnson et. al, 29). Another indicator of occurrence of a reaction involving chemicals is the production of air bubbles. Such reactions that generate bubbles of air go to completion when the air is able to vacate the mixed materials undergoing the reaction process.
Products that are gaseous in nature depict themselves as bubbles only after the mixture undergoing reaction has reached saturation point with the gas. Change in colour is another indicator that can depict occurrence of a reaction involving chemicals (Johnson et. al. 78). When these reaction occurs, two or more substances which are chemical in nature join together to form one or more substances that exhibits molecular structures which are different from the previous individual reagents.
Due to difference in the molecular design, it is highly probable that the new product reflects light in a different way after absorbing from the way the previous substances did. Each and every compound attracts a specific class of colours of light (Johnson et. al, 2004). This kind of attracting diversity forms a chemical mark for determining the presence of that compound.
When the compound undergoes change during a chemical reaction, the chemical mark will be altered, and as a result, the colour of the mixture that has been involved in the reaction will be altered. For example, when a base like Sodium Hydroxide is added to the Phenolphthalein chemical which is clear before the addition of the base, the substance is going to be altered from being clear to becoming pink in colour (Wolny et.al. 58).
However, not all reactions involving chemicals have to be characterized by colour alterations. For instance, when Zinc Oxide is subjected to heat, it is going to undergo change from its previous colour of white to yellow, while in real sense no chemical reaction would have occurred. Another example is that under specific amounts and r the correct conditions, carbon, which is black in colour, can be joined with colourless hydrogen and oxygen to generate sugar which is white in colour (Wolny et.al. 79).
Furthermore, change in temperature is also a characteristic feature denoting an occurring of a reaction involving chemical substance. For bonds holding together a chemical substance to be broken, it requires energy that disintegrates these holding forces and as an outcome of a new chemical substance being generated, energy is emitted (Wolny et.al. 81). When the process of converting chemical substances into new products incorporates a lot of disintegration of holding forces than the creation of these forces, it needs energy which is often absorbed from the immediate environment, and as a result creating a cooler immediate surroundings.
When the chemical reactions involve more of creation of holding forces than their disintegration, a lot of energy is generated and therefore making the immediate surroundings hotter. Therefore reactions involving chemical substances may lead to rise in temperature as a result of heat being evolved whereas it can also result to lowering of temperature when temperature within the non-isolated system acquires heat (Wolny et.al. 91).
The important difference is that these alterations are the product of changes in the chemical characteristic of the substances participating in the process. For instance, when wood undergoes combustion in the presence of air; once wood is converted into ash, it becomes a totally different mixture than it was previously. As an obvious thing, the ashes cannot be made back into wood again. This describes an irreversible chemical reaction. Another example is when an alkali is mixed with acid. There will be generation of heat and hence temperature levels ascends, whereas dissolving a chemical substance like Ammonium Nitrate (NH4NO3) water which is a universal solvent will lead to heat being absorbed and hence a subsequent cooling of the surrounding (Wolny et.al. 92).
Emission of light is also another characteristic feature denoting a reaction of chemical substances have taken place. During the formation of forces holding together particles of some substances undergoing reactions, energy generated can sometimes be emitted in form of light as in the case of reactions undergoing burning. Another illustration is that of living creatures that produce glowing scenario in darkness such as firefly which generate light void of heat by use of chemical reactions (Johnson et. al, 96).
Additionally, reactions involving chemical substances have been identified by changes in the volume in the vessel where the reactions are taking place. One of the characteristics of a compound is its density. When new substance is produced as the other is depleted during a chemical reaction, the alteration in the density can make the mixture undergoing reaction to either increase or reduce in size as the process continues.
Sometimes this change in volume can be great and very fast, and as a result it may lead to explosions (Wolny et.al, 91). A change in both the boiling points and melting points can happen during a chemical reaction process. Boiling point or melting point is another feature of a compound, which is made up of two or more chemical substances that have been chemically combined. During a reaction, the composition of the mixture is altered and hence the boiling point and melting point also is altered.
Chemical changes are also accompanied by a change in a manner in which electricity can be conducted. Several changes which are chemical in nature generate or deplete ions within the solution (Wolny et.al. 191). This alteration in the quality and concentrations of ions will result to changes in the mixture that is undergoing reaction concerning its capability to conduct electrical current. The bubbling of a substance is also another observation that denotes that a chemical reaction has taken place.
Some substances like water produce bubbles when it is heated up to boiling point, and this happens mainly because heat has been injected into the water thus raising the movement energy of its molecules (Wolny et.al. 111). However, this is not the case with hydrogen peroxide, which produces bubbles when exposed to oxygen yet it has not been heated. Many chemical changes like the one of hydrogen peroxide, indicates that production of bubbles does not always happen when two or more chemical substances react, but when one of these indicators is noticed, it implies that a chemical reaction may have occurred.
A change in taste or smell is also an indicator that several chemical substances have reacted and formed a new chemical product. The formation of sugar when carbon has been combined with oxygen and hydrogen is an example that explains this. Some chemical reactions may have toxic reactants or may also produce poisonous compounds as end products, and therefore extremely unsuitable to the taste buds (Wolny et.al. 125).
The smelling too can change and can denote a chemical reaction taking place. For instance, sulphur has no odour when it is in form of an element. However, when it is combined with hydrogen, the end product is hydrogen sulphide (H2S) which is a bad smell as well as being a gas that is highly toxic. Another parameter that can indicate occurrence of a chemical reaction is the change in form or state of a chemical substance like during reactions involving combustion, burning of the fuel with an oxidizing agent for instance oxygen or fluorine leads to the formation of new products, which are in a different form or state compared to the previous reactants (Wolny et.al. 136). Another example that illustrates the same is the chemical reaction involving an acid and a base to form a salt and water such as sodium hydroxide (NaOH) combining with hydrochloric acid (HCl) to form sodium chloride and water. The production of a sound is also a feature exhibited by some chemical substances upon being converted to new products. Many chemical reactions generates sound by producing explosions or reacting very violently as well as the fireworks that make a whistling sound that is caused by the burning of a specific chemical substance.
Bateman, Graham. Chemical Reactions. Redding, Conn.: Brown Bear Books, 2010. Print.
Johnson, Rebecca L. Chemical Changes. Washington, D.C.: National Geographic Society, 2004. Print.
Wolny, Philip. Chemical Reactions. New York: Rosen’s Pub. Rosen Central, 2011. Print.