Some Examples Of Chemical Changes
Burning a magnesium strip. • Physical Change - the object is not changed substantially. It still has the same properties as the original paper. 10 M CuCl2 solution so that 52. For example, adding vinegar to baking soda creates a familiar foaming action but does not involve a color change. ! A chemical change does change the chemical properties of a substance. Give two examples of a physical change: Give two examples of a. One of our main missions at our school is to prepare students for college. A physical change is represented by the melt down of the wax candle into liquid wax. Kitchen chemistry: Chemical changes during cooking Description This shows experiments in which different cuts of meat are cooked under different conditions to determine the optimum cooking temperature. 1 Energy changes in chemical reactions (ESBQJ) What causes the energy changes in chemical reactions? (ESBQK) When a chemical reaction occurs, bonds in the reactants break, while new bonds form in the product. For example, ice, liquid water, and steam. The more common types of chemical reactions are as follows: are examples of combination reactions. The energy produced keeps us warm, maintain and repair bodies, and makes us able to move about. A change in color is not always a chemical change. Physical change c. It turns methyl orange to red. You can explain that shape is a physical property. If the chemical properties of a substance remain unchanged and the appearance or shape of an substance changes it is called a a. Report any defects in plant/ equipment immediately to the employer as appropriate. Chemical definition is - of, relating to, used in, or produced by chemistry or the phenomena of chemistry. The value is negative as the chemical reaction releases heat into the environment. 6 kJ of energy. Chemical reactions are so important because not only do they change the property of the substances that go into the reaction, they also store or release energy. Can you think of some very good examples of chemical energy?. The ten examples of chemical changes are : Burning of coal, wood, paper, kerosene, etc. These properties may change if tin was heated to its melting point, where it would become a liquid, or if it was shown under a light with a color other than white. The skin reactions to fragrance chemicals can produce rashes, hives, dermatitis, or eczema. A chemical reaction is a process in which one or more substances change to make one or more new substances. ' The physical changes are what. The chemical reactions occur between the electrolyte and the cathode and between the electrolyte and the anode. To control the system we need to use the information provided by the sensor. Extraction (literally, "taking out by force") is a useful technique for separating compounds such as I 2 and KMnO 4 that have different polarities. Examples of Chemical Changes burning wood mixing acid and base digesting food Physical Changes: Physical changes are concerned with energy and states of matter. When a substance undergoes a physical change it does not lose its original properties when changing from one phase to another. No new substance is formed in a physical change; water moving between states of matter, a Popsicle melting, and a paper crumbled are examples of physical changes. Burning a magnesium strip. What are some examples of reversible chemical reactions? Chemistry I know there are physical changes such as water changing its state from ice to liquid water which can be easily reversed (changing the liquid water back into solid, ice form). Some chemical. Crandon Chicago Il 60617 (312) 535-6425 Objectives: Grade 2 1. It is also used in filling gas of light bulbs. The ten examples of chemical changes are : Burning of coal, wood, paper, kerosene, etc. The millions of different chemical compounds that make up everything on Earth are composed of 118 elements that bond together in different ways. After students explore one example of an endothermic change and one example of an exothermic change, they are then asked to explore the connection between energy changes and chemical reactions. Mixing an acid with a base, producing water and salt. Changes that may accompany a chemical reaction include colour, appearance and production of new materials, for example, a gas. Chemical Weathering Chemical weathering includes the effect of weathering on molecules and atoms. The new substance has different properties than either of the original substances and also has a different energy content. Absorption of water into a towel. It is easy to differentiate between a physical and chemical change. As salinity and pH increase seaward, some dissolved substances, such as Fe (iron), may precipitate to form solids and then remove other dissolved elements, such as Mn (manganese), onto their surfaces. Science 8 Laboratory Experiment OBSERVING CHEMICAL CHANGES (Marking Scheme) Maximum = 9 (2) OBSERVATIONS: Copper(II) chloride is a blue-green solid. Some physical properties are extensive properties, properties that depend on the amount of matter present. chemical and physical transitions between rivers and oceans. Below are some signs that a chemical change may have occurred. Most systems or processes depend at some level on physical and chemical subprocesses that occur within it, whether the system in question is a star, Earth’s atmosphere, a river, a bicycle, the human brain, or a living cell. and Data Sheets. For example, living things respond to changes in light, heat, sound, and chemical and mechanical contact. For example, your textbook, trees, table, etc. Answer: In burning of candle some of the wax melts, which is physical change, while most of the wax burnt, which is a chemical change. The fruit fly experiments also provided an early example of. No Change to Molecules. A chemical reaction is involved in this breakdown. Some chemical changes are a little more difficult to spot, like when a nail rusts. (Examples: ashes after wood burning, rust in iron. These changes can trigger migraine headaches, the ability to concentrate, dizziness, and fatigue. Scenarios which represent examples of physical changes are as follows. A chemical reaction is a process in which the identity of at least one substance changes. Usually, the output, as measured by the sensor is subtracted from the input (which is the desired output) as shown below. Food has the same problem. One example of chemical change is lighting a gas stove to cook material. Chemical Changes Bonnie J. These bubbles, and the liquid mixture left behind, cannot be turned back into vinegar and bicarbonate of soda again. Here is another example of a chemical change: N 2 (g) + 3H 2 (g) ---> 2NH 3 (g) While all three substances are gases, the two reacting. The United States, desiring to reward and celebrate significant achievements in Green Chemistry, has given out an annual award since 1996, the Presidential Green Chemistry Challenge Award. Spontaneous temperature changes very often accompany the chemical reactions. “As health care providers, we can do a better job of recognizing and treating the mental health consequences of things like sexual abuse and gender-based violence and the stressors that women experience more than men. Lab Techniques; Density: Atomic Spectroscopy and Light. It includes changes that alter the identity of a substance. Rusting of iron 5. Color Shape can change the substance but not its chemical composition. Electrolysis of water to form hydrogen and oxygen. perfume evaporating on your skin - physical. Can you recognize the chemical and physical changes that happen all around us? If you change the way something looks, but haven’t made a new substance, a physical change (P) has occurred. A chemical reaction is a process that changes some chemical substances into others. If the containing vessel bursts, its contents are free to expand and a shock wave is formed. Evaporation of water. A change in colour also takes place in this chemical reaction. 8 ° C) and. carbon dioxide) are formed. This is because the composition of the car has not changed. When you chemically change a substance, it is generally not a reversible process. changes in them. • Related to the kinds of chemical changes that substances undergo Examples – Photosynthesis • In the presence of sunlight and chlorophyll, carbon dioxide reacts with water to produce glucose and oxygen – Metal Rusts • Iron reacts with oxygen and water to produ ce iron oxides and iron hydroxides (rust). burning of fuels 4. Respiration / photosynthesis 8. For example, your textbook, trees, table, etc. 25 g CuCl2?. Students record their notes in a Chemical vs physical change notes organizer. Below are some example elements and compounds and their chemical properties. Some catalysts actually change during the course of the chemical reaction, but then are returned to their original state at the end of the reaction. When the new product is generated, there will a change of energy in the reaction. Chemical change A chemical change (also called chemical reaction) occurs when two or more chemical substances react to produce a new substance (or substances) with a different set of properties. Yes; new substances formed, as evidenced by the color changes and bubbles. Another general example is the use of chemically reactive compounds that interact with the contaminant and change its structure into a form that is non-toxic. In the process of chemical change, the composition of the original matter is altered. Adding oxygen to iron creates iron oxide (rust). 1) The combustion of methane (natural gas) is highly exothermic (it gives out a lot of heat). Learning About Chemical Reactions For Students Do you ever wonder how a nail becomes rusty after it is exposed to water, or how water can turn from ice to steam when heat is applied? Chemical reactions occur every day and most chemical reactions are natural occurrences at home or at school. combustion (burning) of wood. This can happen if a molecule loses some of its atoms, if some atoms are added to a molecule, or if some of the atoms in a molecule get replaced by other atoms. CH4 + 2O2 ==> CO2 + 2H2O Cooking is another example of chemical change; for example, baking bread. After the expiration date, a significant portion of the ingredients in medicine may have undergone chemical change and converted to some other chemical. When a substance undergoes a physical change it does not lose its original properties when changing from one phase to another. Occurs mainly by temperature and pressure changes. Managing changes to processes over the life of a facility is one of nine elements in the RBPS pillar of managing risk. ' The physical changes are what. When the new product is generated, there will a change of energy in the reaction. Some of the chemical energy has now been changed into the kenetic energy of a body flying up into the air. Physical changes are usually about physical states of matter. For example, heat can be released or consumed during both of the reactions. 10 M CuCl2 solution so that 52. more to the right (forward) or more to left. We’ve come to rely on chemicals too much that it pervades every corner of the world, every facet of our lives. Physical explosions are those in which no chemical or nuclear reaction occurs. colour change in leaves 10. No new substance is formed in a physical change; water moving between states of matter, a Popsicle melting, and a paper crumbled are examples of physical changes. In a chemical reaction, the atoms in the substances rearrange themselves and then join back together in a different way. Acid rain is rain water with a pH of less than 5. Some chemical reactions are much more exciting than others. This is a chemical change, because the. Refer to the StoPGoPS model for problem solving. My knowledge of science is limited, so if I have made a blunder in my descriptions, please let me know so that I can correct them! Here are the top 10 amazing chemical reactions. A side-by-side comparison to physical change makes the matter crystal clear. Let the children observe a raw egg. A chemical change (chemical reaction) is a change of materials into other, new materials with different properties, and one or new substances are formed. No Change to Molecules. " A nail rusting: an example of chemical change. Crandon Chicago Il 60617 (312) 535-6425 Objectives: Grade 2 1. Evaporation of water. Below are some example elements and compounds and their chemical properties. Chemical reactions occur between an acid and an alkaline--baking powder or baking soda--forming gas pockets, which make the dough rise. Because of the way they operate, hormones are sometimes called "chemical messengers. 8- Artificial flavor and color : Many processed foods have chemicals that give it a specific flavor or color and help preserve it. Other Names- Some elements have more than one name or spelling. When you tear a piece of paper, it is still paper; it's just that the pieces are smaller. A chemical change is when the substance or object changes such as burning a piece of paper into ashes. We understand there is a risk of groundwater contamination and the environmental issues that brings, but we're still not entirely sure what it means for our own health. Students will then follow the instructions to perform density tests and chemical tests on the plastic samples. Chemical equilibrium is a very delicate system that represents a perfect balance between forward and reverse reaction. Burning a magnesium strip. This is because the composition of the car has not changed. When the new product is generated, there will a change of energy in the reaction. On the contrary, the examples of chemical change are combustion, metabolism, cooking of egg, etc. Chemical weathering - process by which the internal structure of a mineral is altered by the addition or removal of elements. This change of state is a physical change since scooping up the water and returning it to the freezer reverses it. When you chemically change a substance, it is generally not a reversible process. The LM35 temperature sensor, for example, produce. A physical change does not produce a new substance. Naming Metal-Nonmetal Compounds If one of the two compounds is a metal, then the naming convention changes a bit. Quizlet flashcards, activities and games help you improve your grades. This change is seen in the fact that some chemical bonds are broken and some bonds are newly made. It includes changes that alter the identity of a substance. So much energy is released that the hydrogen gas released spontaneously burns in the air. Different foods store different amounts of energy. Eventually you should be able to look at the formula of a compound and state some. This first series is based on 5th grade science. Recycling of basic chemicals Sulfuric acid. For example, melting and boiling are endothermic but freezing and condensing are exothermic. RE: What are 5 Physical Changes and 4 Chemical Changes in everyday life? So, we were doing experiments in class and the teacher told us to bring close toe shoes the day beforewell, i forgot and now i have to find 5 physical changes and 4 chemical changes at my house, describe the materials before and after, and record why it is a physical changeI am so confused. How Rocks Change Introduction Does it seem to you that rocks never change? For example, if you find a chunk of granite today, can you expect that it will still be granite at the end of your lifetime? That may well be true — but only because our lifetimes are very short relative to the history of the earth. This is because the composition of the car has not changed. For Ex:1)Reaction between zinc and dilute sulphuric acid to form hydrogen gas. When matter changes from one state to another, but keeps its identity it undergoes a physical change. Chemical equations are written with the symbols of materials to include elements, ionic or covalent compounds, aqueous solutions, ions, or particles. Digestion relies on chemical reactions between food and acids and enzymes to break down molecules into nutrients the body can absorb and use. The reaction of sodium and water is one of the easiest examples to show you the chemical. The difference between a physical and chemical property is straightforward until the phase of the material is considered. TEK: I can differentiate between physical and chemical changes and properties~ Terms~ Physical Change: change which physical properties of a substance are altered but the substance remains the same. Other people argue that there is a chemical change because the material present in solution has different properties than the separated pure water and pure salt. A chemical change can produce amazing explosions, like fireworks. Effects On Soil and Crops. CHEMICAL KINETICS: INTRODUCTION TO RATE OF REACTION. Phases (States) of Matter with Examples | Online Chemistry Tutorials. Some chemical reactions to keep in mind while doing this tasty experiment are: Heat helps baking powder produce tiny bubbles of gas, which makes the cake light and. Some results of chemical reactions are shown in Figure 1. Each type has its own defining characteristics in terms of reactants and products. Report any defects in plant/ equipment immediately to the employer as appropriate. It can leach lead from pipes especially if the water is soft. • Physical Change – the object is not changed substantially. No new substance is formed, there is little or no heat change and its usually easy to reverse the process. Chemical Change - click on a type of change to observe the molecular details of the process ; Physical or Chemical Change? - Determine if each is a physical or chemical change. Most chemical changes, on the other hand, take longer time to become discernible. There are approved additives that have been shown in subsequent independent studies to harm health, and are in the "Avoid" category in Chemical Cuisine. An example of a chemical change (reaction) is the combining of two hydrogen molecules with one oxygen molecule to form two water molecules. Any chemical change involves two sets of substances: reactants and products. 10 M CuCl2 solution so that 52. " Hormones are very different from each other—depending on the functions they perform—and they occur in both plants and animals. using extract ventilation where provided, and report any defects. Theories-in-action: Some theoretical and empirical issues in the study of students' conceptual frameworks in science. So much energy is released that the hydrogen gas released spontaneously burns in the air. There are many examples of chemistry in daily life, showing how prevalent and important it is. Then the further expansion as a part of the phase change keeps the ice floating with some 8% of its mass above the surface. No Change to Molecules. asked by Anonymous on February 25, 2010; science. A glass breaks. For example, salt dissolved in water can be recovered by allowing the water to evaporate. Chemical Separations One of the most important and time-consuming activities in chemistry involves isolating, separating, and purifying chemical compounds. (Caution the observers to be careful. Formation of curd from milk 3. It's a chemical reaction. formation of wine 9. A chemical reaction is involved in this breakdown. Both a physical and chemical change d. One example of a physical change is one suggested by Cathrine. colour change in leaves 10. From the above explanation, the concept of physical and chemical change and the difference between physical and chemical changes are evident. Rusting of iron. There are also proteins such as villin or filamin that bind microfilaments together side by side to produce bundles of actin filaments. Managing changes to processes over the life of a facility is one of nine elements in the RBPS pillar of managing risk. When placed in water, the crystals turn bright green with a slight blue tinge in the water above the crystals. It turns methyl orange to red. , from the raw crude oil. Some sulfuric acid is produced from 'spent' (used) acid and related compounds such as ammonium sulfate which is a by-product in the manufacture of methyl 2-methylpropenoate. While it's not always easy to tell a chemical change has occurred (as opposed to a physical change), there are some telltale signs. Physical & Chemical Changes study guide by ConnorPat includes 32 questions covering vocabulary, terms and more. • Related to the kinds of chemical changes that substances undergo Examples – Photosynthesis • In the presence of sunlight and chlorophyll, carbon dioxide reacts with water to produce glucose and oxygen – Metal Rusts • Iron reacts with oxygen and water to produ ce iron oxides and iron hydroxides (rust). The enthalpy change for a reaction depends upon the state of the reactants and products. Unless one is extremely careful and precise in measuring mass, the change in mass is immeasurably small in chemical reactions. Below are some example elements and compounds and their chemical properties. To investigate some characteristics of chemical changes. Chemical changes happen on a much smaller level. The ripening of fruits, photosynthesis, tarnishing of iron, burning of woods, digestion of foods, and even cooking foods are few examples of chemical changes and chemical reactions happening around us and even inside our bodies. Most systems or processes depend at some level on physical and chemical subprocesses that occur within it, whether the system in question is a star, Earth’s atmosphere, a river, a bicycle, the human brain, or a living cell. With these characteristics it is easier to know what kind of change took place. A physical change is any change in matter that involves the substance going from one physical state to another. Chemical changes lead to the formation of substances that help grow our food, make our lives more productive, cure our heartburn, and much, much more. Hydrogen reacts with oxygen to form water, according to the following equation:. 2)Reaction between sodium carbonate and dilute hydrochloric acid to form carbon dioxide gas. Physical Change Chemical Change. In this case, borax (sodium borate) changes the sticky properties of Elmer’s glue, to make a fun to play with putty. For example: A highly toxic chemical can have a low health hazard if it is used with proper precautions and care. You can explain that shape is a physical property. Chemical Sensitivities and Perfume. When a physical change occurs, the nature and propierties are still the same, they are the same substances. An example is the substance called methyl yellow, which imparts a yellow colour to an. After the expiration date, a significant portion of the ingredients in medicine may have undergone chemical change and converted to some other chemical. charcoal heating a grill - see below. Question 1: 10 mL of a colourless solution labelled sulfuric acid is added to 10 mL of a colourless solution labelled barium nitrate in a test tube. Germination of seeds. Metal + Oxygen (from air) Metal Oxide For example 2 Mg + O 2 2 MgO (Magnesium Oxide) MgO + H 2O Mg(OH) 2 (Magnesium Hydroxide) Metal hydroxide changes red litmus blue which shows its basic characteristics. Science 8 Laboratory Experiment OBSERVING CHEMICAL CHANGES (Marking Scheme) Maximum = 9 (2) OBSERVATIONS: Copper(II) chloride is a blue-green solid. Elementary Reactions and Microscopic Reversibility. There is good epidemiological evidence that this can have a relatively small but measurable. Figure 1 The chemical industry is one of the largest manufacturing industries in all developed and emerging countries. Change of State. Elmer’s glue is polyvinyl acetate, and when sodium borate is added to it, a cross-linked polymer is created giving. Watchout for: Some reactions come from industrial pocesses such as the formation of bleach (ClO-ion) from Cl 2 and. Proceed with caution. It includes changes that alter the identity of a substance. Some its components may be eliminated or rearranged while other elements may be added to achieve a new substance unique to the substances combined. After students explore one example of an endothermic change and one example of an exothermic change, they are then asked to explore the connection between energy changes and chemical reactions. Water molecules can be broken down into hydrogen and oxygen molecules by a chemical reaction called electrolysis. 6 kJ/mol of O 2. Some minerals, such as Torbernite, have a varying amount of water within fixed limits. digestion of food 5. combustion (burning) of wood. Chemical reactions differ from physical changes, which include changes of state, such as ice melting to water and water evaporating to vapor. The reaction of sodium and water is one of the easiest examples to show you the chemical. This can happen if a molecule loses some of its atoms, if some atoms are added to a molecule, or if some of the atoms in a molecule get replaced by other atoms. This is a hands on activity that demonstrates how chemical reactions change the properties of a substance. In the cases where chemical changes can be reversed, the system is usually in a form of equilibrium and it involves a second chemical change to reverse the original chemical change. When we heat food, orientation of the atoms change. An example of a chemical change (reaction) is the combining of two hydrogen molecules with one oxygen molecule to form two water molecules. No new substance is formed, there is little or no heat change and its usually easy to reverse the process. Hickerson Horace Mann 8050 S. This list is aimed at some of the more exotic and amazing reactions that most of us have not seen or experienced. Physical changes are usually about physical states of matter. Chemical changes produce something new. In some cases, it may be hard to tell whether a chemical or physical change occurred. Elmer’s glue is polyvinyl acetate, and when sodium borate is added to it, a cross-linked polymer is created giving. What are some examples of chemical and physical changes? Change of state (such as from solid to liquid or from gas to liquid). While it's not always easy to tell a chemical change has occurred, there are some telltale signs. a hot glass cracking when placed in cold water. Types of Chemical Changes. Explicit instruction/Teacher modeling. Here are some chemical pollution examples: Air Pollution. Main Experiment Menu; Introductory Information. Chemical energy is the energy that is stored in chemical form, in the bonds of atoms and molecules. An example of chemical weathering is acid rain. PHYSICAL PROPERTIES OF ACIDS. Physical change occurs faster and sometimes instantaneously. Chemical changes may cause a substance to change color, change temperature, produce bubbles, or (in liquids) produce a precipitate. Synthesis, decomposition, combustion, and oxidation are some examples of chemical changes (reactions) of matter. Chemical change produces new substances that were made from two or more elements. and Data Sheets. Eventually you should be able to look at the formula of a compound and state some chemical property. When performing an experiment to study the conditions necessary for rusting, some water is boiled and allowed to cool. Effects On Soil and Crops. Learning About Chemical Reactions For Students Do you ever wonder how a nail becomes rusty after it is exposed to water, or how water can turn from ice to steam when heat is applied? Chemical reactions occur every day and most chemical reactions are natural occurrences at home or at school. (sulphur and sugars, for example) or retarders (salt, for instance), high pressure or. Our online chemical changes trivia quizzes can be adapted to suit your requirements for taking some of the top chemical changes quizzes. Some its components may be eliminated or rearranged while other elements may be added to achieve a new substance unique to the substances combined. NaOH CuSO4 – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow. A substitution is a mutation that exchanges one base for another (i. The students will distinguish between physical and chemical changes. Water molecules can be broken down into hydrogen and oxygen molecules by a chemical reaction called electrolysis. Peeling an apple is an example of a physical change. SAFETY INTERVIEW QUESTION & ANSWER. The result is that they contaminate our environment, resulting in chemical pollution. Yet physical changes are all around, just waiting for you to notice them! You can be certain what you observe is a physical change if the change does not alter the object's chemical structure. If someone tries to use some other substance in place of gold, then it will not have all the same physical and chemical properties of gold. The changes taking place around us are broadly classified according to their nature and effect on environment. ELEMENT OVERVIEW. A good example of physical change is ice melting into water. If the substance has been changes into another substance, a chemical change (C) has occurred. more to the right (forward) or more to left. Because of the way they operate, hormones are sometimes called "chemical messengers. Some chemical reactions are much more exciting than others. A formation of a solid may take place when two gases are joined together. This (1) biochemical change leads to a (2) cellular change (in this case an increase in nerve activity). Intensive properties. The vast number of chemical reactions can be classified in any number of ways. The chemical and physical properties of the new substances differ from those of the original substances. 10 M CuCl2 solution so that 52. Find out what substances dissolve in water and lots of other interesting chemistry related facts. Ten or more examples of chemical changes!?!?!? Answer Questions To what volume should you dilute 133 mL of an 8. But the distinction between physical and chemical change can be misleading and confusing at times. The reference to a physical state involves solids, liquids, and gases. The types of physical changes can vary. (a Quia quiz). ' The physical changes are what. Disposable batteries (batteries that can't be recharged) work until the reactive chemistry of the electrodes and electrolytes is exhausted. • Chemical Change - a new substance has been created • Evaporation - change of a liquid into a gas • Condensation - change of a gas into a liquid • Distillation - process by which water is evaporated and then condensed back. For example, take this stack of paper, and wading it into smaller pieces is a physical change. Physical change occurs faster and sometimes instantaneously. ' Examples of Chemistry in the Real World. Effects On Soil and Crops. A chemical change (chemical reaction) is a change of materials into other, new materials with different properties, and one or new substances are formed. For example, salt dissolved in water can be recovered by allowing the water to evaporate. Besides that, the emission of methane and carbon dioxide will also affect climate changes. Freezing d. Chemical change A chemical change (also called chemical reaction) occurs when two or more chemical substances react to produce a new substance (or substances) with a different set of properties. This definition of chemical change for kids brings science to life by pointing out some of the chemical changes that happen in our homes everyday. charcoal heating a grill - see below. Temperature Change of State. An example of a chemical change is the reaction between sodium and water to produce sodium hydroxide and hydrogen. "No two substances have identical physical and chemical properties. If the bubbles were caused by the decomposition of a molecule into a gas (such as H 2 O →H 2 and O 2 ), then boiling would be a chemical change. A physical change is a change to a sample of matter in which some properties of the material change, but the identity of the matter does not. Some signs of a chemical change are a change in color and the formation of bubbles. The speed or rate of a chemical reaction is the change in concentration of a reactant or product per unit time. Physical and Chemical Changes. A piece of paper burns. Watchout for: Some reactions come from industrial pocesses such as the formation of bleach (ClO-ion) from Cl 2 and. Changes in protein shape can be driven in a unidirectional manner by the expenditure of chemical energy. When you chemically change a substance, it is generally not a reversible process. Certain variables play a role in a person's susceptibility to exposure and adverse health effects such as age, gender, genetics, pregnancy or other health conditions.