5 paragraph essay chemical reactions
Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. Some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. Understanding chemical changes is a major part of the science of chemistry.
Chemical reaction
The space shuttle—and any other rocket-based system—uses chemical reactions to propel itself into space and maneuver itself when it gets into orbit. The rockets that lift the orbiter are of two different types. The three main engines are powered by reacting liquid hydrogen with liquid oxygen to generate water.
Then there are the two solid rocket boosters, which use a solid fuel mixture that contains mainly ammonium perchlorate and powdered aluminum. The chemical reaction between these substances produces aluminum oxide, water, nitrogen gas, and hydrogen chloride. Chemistry is largely about chemical changes. Indeed, if there were no chemical changes, chemistry as such would not exist!
Chemical changes are a fundamental part of chemistry. Because chemical changes are so central, it may be no surprise that chemistry has developed some special ways of presenting them.
A chemical reaction expresses a chemical change. For example, one chemical property of hydrogen is that it will react with oxygen to make water. We can write that as follows:. We can represent this chemical change more succinctly as. But substances can also be represented by chemical formulas. Remembering that hydrogen and oxygen both exist as diatomic molecules, we can rewrite our chemical change as. This is an example of a chemical equation A concise way of representing a chemical reaction.
The initial substances are called reactants An initial substance in a chemical equation. Unfortunately, it is also an incomplete chemical equation. The law of conservation of matter says that matter cannot be created or destroyed. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products.
If we count the number of hydrogen atoms in the reactants and products, we find two hydrogen atoms. But if we count the number of oxygen atoms in the reactants and products, we find that there are two oxygen atoms in the reactants but only one oxygen atom in the products.
What can we do? Can we change the subscripts in the formula for water so that it has two oxygen atoms in it? No; you cannot change the formulas of individual substances because the chemical formula for a given substance is characteristic of that substance. What you can do, however, is to change the number of molecules that react or are produced.
We do this one element at a time, going from one side of the reaction to the other, changing the number of molecules of a substance until all elements have the same number of atoms on each side. To accommodate the two oxygen atoms as reactants, let us assume that we have two water molecules as products:. The 2 in front of the formula for water is called a coefficient A number in a chemical equation indicating more than one molecule of the substance.
Now there is the same number of oxygen atoms in the reactants as there are in the product. But in satisfying the need for the same number of oxygen atoms on both sides of the reaction, we have also changed the number of hydrogen atoms on the product side, so the number of hydrogen atoms is no longer equal.
No problem—simply go back to the reactant side of the equation and add a coefficient in front of the H 2. The coefficient that works is There are now four hydrogen atoms in the reactants and also four atoms of hydrogen in the product.
There are two oxygen atoms in the reactants and two atoms of oxygen in the product. The law of conservation of matter has been satisfied. When the reactants and products of a chemical equation have the same number of atoms of all elements present, we say that an equation is balanced A condition when the reactants and products of a chemical equation have the same number of atoms of all elements present.
All proper chemical equations are balanced. If a substance does not have a coefficient written in front of it, it is assumed to be 1. Also, the convention is to use all whole numbers when balancing chemical equations.
Write and balance the chemical equation for each given chemical reaction. Let us start by simply writing a chemical equation in terms of the formulas of the substances, remembering that both elemental hydrogen and chlorine are diatomic:. There are two hydrogen atoms and two chlorine atoms in the reactants and one of each atom in the product. We can fix this by including the coefficient 2 on the product side:. Now there are two hydrogen atoms and two chlorine atoms on both sides of the chemical equation, so it is balanced.
We have two carbon atoms on the left, so we need two carbon dioxide molecules on the product side, so that each side has two carbon atoms; that element is balanced. We have six hydrogen atoms in the reactants, so we need six hydrogen atoms in the products. We can get this by having three water molecules:. Now we have seven oxygen atoms in the products four from the CO 2 and three from the H 2 O.
That means we need seven oxygen atoms in the reactants. However, because oxygen is a diatomic molecule, we can only get an even number of oxygen atoms at a time. We can achieve this by multiplying the other coefficients by We can get 14 oxygen atoms on the reactant side by having 7 oxygen molecules:.
As a check, recount everything to determine that each side has the same number of atoms of each element. This chemical equation is now balanced. Write and balance the chemical equation that represents nitrogen and hydrogen reacting to produce ammonia, NH 3. Special conditions, such as temperature, may also be listed above the arrow.
For example,. Write and balance the chemical equation described by Exercise 1. Write and balance the chemical equation described by Exercise 2. Write and balance the chemical equation described by Exercise 3.
Write and balance the chemical equation described by Exercise 4. The formula for propane is C 3 H 8. How would you write the balanced chemical equation in Exercise 10 if all substances were gases?
How would you write the balanced chemical equation in Exercise 12 if all the substances except water were gases and water itself were a liquid? Up to now, we have presented chemical reactions as a topic, but we have not discussed how the products of a chemical reaction can be predicted.
Here we will begin our study of certain types of chemical reactions that allow us to predict what the products of the reaction will be. A single-replacement reaction A chemical reaction in which one element is substituted for another element in a compound.
The hydrogen atoms in HCl are replaced by Zn atoms, and in the process a new element—hydrogen—is formed. Another example of a single-replacement reaction is. Here the negatively charged ion changes from chloride to fluoride. A typical characteristic of a single-replacement reaction is that there is one element as a reactant and another element as a product. Not all proposed single-replacement reactions will occur between two given reactants.
This is most easily demonstrated with fluorine, chlorine, bromine, and iodine. Collectively, these elements are called the halogens and are in the next-to-last column on the periodic table see Figure 4. The elements on top of the column will replace the elements below them on the periodic table but not the other way around. Thus, the reaction represented by. This is just one of many ways the periodic table helps us understand chemistry.
Will a single-replacement reaction occur? If so, identify the products. Yes; FeCl 2 and I 2. Chemical reactivity trends are easy to predict when replacing anions in simple ionic compounds—simply use their relative positions on the periodic table.
However, when replacing the cations, the trends are not as straightforward. This is partly because there are so many elements that can form cations; an element in one column on the periodic table may replace another element nearby, or it may not. A list called the activity series A list of elements that will replace elements below them in single-replacement reactions. A simple activity series is shown below. Using the activity series is similar to using the positions of the halogens on the periodic table.
An element on top will replace an element below it in compounds undergoing a single-replacement reaction. Elements will not replace elements above them in compounds. Use the activity series to predict the products, if any, of each equation.
Use the activity series to predict the products, if any, of this equation. A double-replacement reaction A chemical reaction in which parts of two ionic compounds are exchanged. A characteristic of a double-replacement equation is that there are two compounds as reactants and two different compounds as products. An example is. There are two equivalent ways of considering a double-replacement equation: either the cations are swapped, or the anions are swapped.
You cannot swap both; you would end up with the same substances you started with. Either perspective should allow you to predict the proper products, as long as you pair a cation with an anion and not a cation with a cation or an anion with an anion. Thinking about the reaction as either switching the cations or switching the anions, we would expect the products to be BaSO 4 and NaCl. Predicting whether a double-replacement reaction occurs is somewhat more difficult than predicting a single-replacement reaction.
5 paragraph essay chemical reactions. Author: Kimbelry, Pages: 14, Words: . A chemical reaction is the transformation of substances on the level of. Chemical reactions and how they break and form bonds between atoms. to indicate the direction of the chemical reaction, though a chemical reaction is not always a "one-way street," as we'll explore further in the next section. 5 years ago.
Chemistry happens in the world around you, not just in a lab. Your body lives and grows thanks to chemical reactions. There are reactions when you take medications, light a match, and draw a breath. These examples of chemical reactions from everyday life are a small sampling of the hundreds of thousands of reactions you experience as you go about your day.
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.
The space shuttle—and any other rocket-based system—uses chemical reactions to propel itself into space and maneuver itself when it gets into orbit. The rockets that lift the orbiter are of two different types. The three main engines are powered by reacting liquid hydrogen with liquid oxygen to generate water.
Examples of Chemical Reactions in Everyday Life
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Properties & Changes 13 Four Elementary Types of Chemical Reactions + Combustion
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Chemical Reactions
If chemistry were compared to a sport, then the study of atomic and molecular properties, along with learning about the elements and how they relate on the periodic table , would be like going to practice. Learning about chemical reactions, which includes observing them and sometimes producing them in a laboratory situation, is like stepping out onto the field for the game itself. Just as every sport has its "vocabulary" — the concepts of offense and defense, as well as various rules and strategies — the study of chemical reactions involves a large set of terms. Some aspects of reactions may seem rather abstract, but the effects are not. Every day, we witness evidence of chemical reactions — for instance, when a fire burns, or metal rusts. To an even greater extent, we are surrounded by the products of chemical reactions: the colors in the clothes we wear, or artificial materials such as polymers, used in everything from nylon running jackets to plastic milk containers. If liquid water is boiled, it is still water; likewise frozen water, or ice, is still water. Melting, boiling, or freezing simply by the application of a change in temperature are examples of physical changes, because they do not affect the internal composition of the item or items involved. A chemical change, on the other hand, occurs when the actual composition changes — that is, when one substance is transformed into another. Water can be chemically changed, for instance, when an electric current is run through a sample, separating it into oxygen and hydrogen gas. Chemical change requires a chemical reaction, a process whereby the chemical properties of a substance are altered by a rearrangement of the atoms in the substance. Of course we cannot see atoms with the naked eye, but fortunately, there are a number of clues that tell us when a chemical reaction has occurred.
Chemical change
Title: Physical and Chemical Changes Purpose: Recognize and distinguish between chemical and physical changes Apparatus and Material: evaporating dish, Bunsen burner, wood splint, test tubes, micro spatula, dropper, mortar and pestle, test tube holder, safety goggles, lab apron. Hypothesis: If we use these materials and use magnets, water, burners, and filters on the mixtures and elements given we should determine what kind of effect these materials given will have on these mixtures and elements, physical or chemical. Label each substance on seven pieces of paper. Physical and Chemical Changes Say you are presented with two beakers, beaker A and beaker B, each containing a white, powdery compound. From your initial observations, you suspect that the two beakers contain the same compound. Describe, in general terms, some experiments in a laboratory that you could do to help prove or disprove that the beakers contain the same compound. Nuclear chemistry is the study of the chemical and physical changes in the nucleus of an atom. The field of nuclear chemistry deals with radioactive elements such as radium, radon and the whole actinides series and the equipment to deal with such elements; such as nuclear reactors. However the subject itself varies because it deals with the scientific areas such as physics, biology, geology and chemistry.
