In your scientific research class, friend may have heard the chemical and also physical changes. However do friend know how to tell the difference between the two? The prize lies in even if it is or not a readjust to a substance results in its molecules gift rearranged.

In this article, us will define chemical and physical and also changes. Climate we"ll take a look at details chemical adjust examples and physical adjust examples to better understand their differences and also similarities.

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So let"s gain started!


When ice cream melts (and goes native a solid to a liquid), it experience a physical change.

Physical adjust Definition

First, let"s talk around physical transforms in chemistry. A physical readjust occurs once a problem or object changes its appearance, phase, or is offered in a mixture. An ext importantly, a physical readjust does not adjust the molecular structure of a substance. And you have the right to reverse a physical readjust to recover all of the initial matter, also if it doesn"t look precisely the same. In various other words, in physics changes, the molecule from before and after the adjust stay the same!

What is an instance of a physics change? Things prefer cutting a piece of document in half, freezing water right into ice or bending few of your mom"s favorite silverware (don"t do that!) room all physical changes. That"s because physical changes only impact a substance"s physics properties, no the composition of their molecules.

Still not sure around what constitutes a physical change? Don"t worry: we"ll destruction into an ext physical change examples in just a minute.


When logs burn, they experience a chemical change.

Chemical change Definition

In contrast, a chemical readjust takes place when the original substance"s the molecules are taken apart and put earlier together into new combinations that are different from the initial combinations. Furthermore, the original issue cannot be recovered. And also unlike physical changes, these transforms usually use a lot more energy, such together heat and also light, due to the fact that the molecule bonds need to be broken in order come rearrange them.

What is an instance of a chemical change, then? some chemical readjust examples include a item of file burning, a pond rusting, or baking a cake. Prefer physical changes, it"s pretty clear the the means these things start and also end are fairly different: a shiny nail turns orange with rust, and also wet dough i do not care a delicious dessert. The reasons these space chemical transforms is the the change happens top top a molecule level. Put another way, the object you start with and also the object you end with are totally different substances.

So, let"s look at some more examples of physical and also chemical transforms to better understand the differences and similarities in between the two.


When this mallet access time the egg, the egg will certainly undergo a (very messy) physics change. (P.S: Don"t try this in ~ home!)

Physical adjust Examples

Earlier we talked about some instances of physical and chemical changes. However sometimes telling a physical adjust from a chemical change can be hard. This is particularly true as soon as physical transforms require or expend energy. The vital thing come remember is the in a physical change, the molecules stay the same.

Let"s look at three various physical adjust examples to far better understand this idea.

Example 1: phase Changes

Phase changes involve changes in size, volume, and also density. Because that instance, when you rotate water right into ice or vapor, this is called a phase change. This is due to the fact that water has 3 phases: solid (ice), fluid (water), and gas (vapor or steam).

It may seem prefer some the the water molecules are lost throughout each phase change: the ice cube gets smaller, and vapor seems to disappear into the air. However, in each of these 3 stages, the water molecules stay the same. And if you were to cool down the vapor, it would certainly reform into water. Cool it under enough, and it would certainly turn earlier into ice. There would certainly be the same amount of hydrogen and also oxygen atoms in the ice cube as there to be in the steam, and these atom will remain in the exact same molecular form in every stages.

Let"s take it a closer look in ~ what"s continue on a molecule level. Vapor is comprised of H20 as with the ice cream cube. The just difference in between vapor and ice is the the separation, personal, instance molecules have actually spread apart in vapor as result of the applications of heat. Meanwhile, in ice, the molecules team closer together since of the lack of heat. Though this phase transforms require energy to be expelled (exothermic reactions) or used (endothermic reactions), the number of atoms and also the form of the molecule in the substance continues to be the same. That"s what makes it a physical change!

Example 2: changes in Size and also Shape


Like we pointed out earlier, physical transforms are all around whether molecules remain the exact same or not. When an item undergoes a physics change, that can come to be a different size and also shape as lengthy as that composition remains the same.

Here"s what us mean: if friend have ever before dropped a piece of glass ~ above the floor, you understand that it will certainly break apart, exploding into a million pieces. If friend really want to, when you brushed up all that glass up right into your dustpan, you could probably fit the all earlier together (even despite it would take a the majority of time and also patience). This is additionally a physical reaction because the glass stays glass. Once it shatters, the glass transforms size and shape, but its molecule don"t change.

This is a physical adjust that only requires a change in size and also shape. While power helped shatter the glass into pieces, no energy was provided to rearrange the molecules.

Example 3: mixture & Solutions

Imagine you room on a day the end at the beach. The sun is shining, the sand is warm, and also the seagulls space trying come steal people"s lunches. After playing in the waves for a bit, you decision to do a sandcastle. You fill your bucket up v sand and also plop it upside down. The sand come out yet it doesn"t stick together. Girlfriend forgot to include water! You shot again, this time through water and voila, you"ve produced your very first tower like a grasp sandcastle architect.

But why didn"t the sand stick with each other the first time? It has to do v a physical property referred to as surface tension. Surface tension describes how solid the shortcut is in between a substance"s molecules. Water has actually a strong surface tension, so adding it come the sand creates a solid enough bond for the sand come cling together instead of fall apart.

What makes this various from a chemistry reaction is the the sand and the water, though mixed together, do not change their molecular structure. The water continues to be water and the sand stays sand. And if you to be to measure the water that will ultimately evaporate once the sandcastle dries, friend will discover that the lot of evaporated water is equal to the quantity of fluid water you included to the sand originally.

This is dubbed a mixture because both building material (the sand and the water) retain their very own physical properties.

The very same is true if you include salt or sugar to water. The seems prefer the salt and sugar dissolve and kind new molecules. Yet if you to be to wait for the water come evaporate, girlfriend would discover that the salt or sugar molecules gain left behind in the glass. This is referred to as a solution.

Solutions different from mixtures in that they room homogenous. A solitary drop of saltwater would have the same number of salt molecule (NaCl) per water molecule (H2O) as another drop taken native the same solution. In a mixture, you might have an ext sand than water in two various handfuls, also if they to be taken indigenous the exact same bucket.

These physical readjust examples should assist you acknowledge the difference in between a physical and also chemical change. Specifically when you compare them to the chemical change examples below.


Dough turning into bread is a tasty instance of a chemistry change.

Chemical change Examples

Both physical and also chemical changes result in one thing transforming into another. whether it"s a glass break or burning a piece of paper, the original item becomes something different.

So how deserve to you phone call the difference in between a physical and also a chemical change? It all comes under to--you guessed it!--the molecules. In a physics change, the molecules stay exactly the very same throughout the transformation. In a chemistry change, however, it"s the molecules themselves that transform!

Here room three examples of chemical transforms to assist you point out the difference!

Example 1: Combustion

Combustion is a chemical reaction between substances, usually consisting of oxygen, that creates heat and also light. The power released by the reaction (in the type of heat and light) is resulted in by the breaking of molecule bonds. As a result, the initial substances transform into entirely various substances since of the rearrangement that molecules, i m sorry is an instance of a chemical change!

For instance, if friend mix oxygen (O2) with a form of hydrocarbon called methane (CH4), the molecule bonds of both substances space broken, which create the heat and light. The bonds then reform to develop two various molecules: carbon dioxide (CO2) and also water (H2O).

Combustion reactions can occur at different rates, too. An instance of a slow reaction is a complement burning. A rapid reaction would certainly be dynamite exploding. The lot of energy released in any kind of combustion reaction counts on just how much energy is necessary to break the molecular bonds. The harder the is to break the bonds, the much more energy is released overall. Yet regardless of whether the reaction is quick or slow, combustion is a chemistry change.

Example 2: Decomposition

Decomposition is rather straightforward. A decomposition reaction is a reaction in which a compound breaks down right into two or an ext simpler substances.

For instance, as soon as an electric present is passed through water (H2O), it deserve to be damaged down right into hydrogen and also oxygen or H2 + O2. In this example, water is damaged down right into its 2 elements. The result is a chemical adjust because the starting and finishing molecules room different.

You"ll an alert that this chemical reaction needed electrical power to happen. Decomposition reactions usually need the applications of warmth from an outside source, making the an endothermic reaction.

Keep in mental that no all decomposition reactions have to breakdown into your elemental forms. More complex substances with longer molecular chains may break down into smaller sized compounds instead of elements. An example of this is as soon as 2Fe(OH)3 (also recognized as ferric oxide) is exposed come heat. Instead of breaking right into its individual molecules, that turns into two compounds: Fe2O3 + 3H2O.

Example 3: Combination

Combination reactions, also called synthetic reactions, room the opposite of decomposition reactions. This reactions happen when two substances (called reactants) are added together to develop one new substance. And because this is a chemistry reaction, the result is a molecular change!

One instance of this would certainly be a nail rusting. While this might seem prefer a decomposition reaction since it seems favor the nail is decomposing and also falling apart. However actually, it"s a chemistry change! stole (Fe) and oxygen (O) incorporate to create the compound iron oxide (Fe2O3), which is rust. And as you have the right to see, it likewise results in a completely new molecule.


What"s Next?

Understanding chemical and also physical reaction in only one component of what you require to understand in order to success on the AP Chemistry Exam. We"ve gathered together the most vital AP Chem topics into this ultimate guide.

Taking IB Chemistry instead? Here"s the complete IB Chemistry syllabus, a comprehensive study guide, and also some examples of past files from the IB Chemistry exam.

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Need help understanding other chemistry concepts? Learn how to balance chemistry equations step-by step, what the 11 solubility rule are, and when you must use the solubility constant (Ksp).