In your scientific research class, friend may have actually heard of chemical and physical changes. Yet do girlfriend know how to tell the difference in between the two? The price lies in whether or not a change to a substance outcomes in that molecules being rearranged.

In this article, us will specify chemical and physical and changes. Climate we"ll take it a look at at certain chemical adjust examples and physical adjust examples to far better understand their differences and similarities.

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When ice cream melts (and goes from a solid come a liquid), it undergoes a physics change.

Physical adjust Definition

First, let"s talk around physical alters in chemistry. A physical adjust occurs as soon as a problem or object transforms its appearance, phase, or is supplied in a mixture. An ext importantly, a physical adjust does not adjust the molecular structure of a substance. And also you can reverse a physical readjust to recover all of the initial matter, even if that doesn"t look specifically the same. In other words, in physical changes, the molecule from before and after the adjust stay the same!

What is an instance of a physical change? Things favor cutting a piece of record in half, freeze water into ice or bending several of your mom"s favourite silverware (don"t carry out that!) space all physics changes. That"s because physical transforms only impact a substance"s physical properties, not the composition of your molecules.

Still no sure around what constitutes a physics change? Don"t worry: we"ll destruction into more physical readjust examples in simply a minute.


When logs burn, they undergo a chemistry change.

Chemical readjust Definition

In contrast, a chemical adjust takes location when the original substance"s that molecules space taken apart and put back together into new combinations that are different from the initial combinations. Furthermore, the original issue cannot be recovered. And also unlike physical changes, these changes usually use a lot an ext energy, such as heat and light, due to the fact that the molecule bonds need to be damaged in order to rearrange them.

What is an instance of a chemical change, then? part chemical readjust examples incorporate a piece of paper burning, a pond rusting, or baking a cake. Prefer physical changes, it"s pretty clear that the way these points start and end are rather different: a glowing nail turns orange v rust, and wet dough i do not care a very delicious dessert. The reasons these room chemical transforms is that the adjust happens top top a molecule level. Put another way, the thing you start with and also the object you end with are completely different substances.

So, let"s look at some an ext examples of physical and chemical alters to much better understand the differences and similarities in between the two.


When this mallet hits the egg, the egg will undergo a (very messy) physical change. (P.S: Don"t shot this in ~ home!)

Physical readjust Examples

Earlier us talked around some instances of physical and chemical changes. But sometimes informing a physical change from a chemical readjust can be hard. This is especially true when physical changes require or expend energy. The essential thing to remember is that in a physical change, the molecules continue to be the same.

Let"s look in ~ three different physical change examples to far better understand this idea.

Example 1: phase Changes

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

It might seem choose some that the water molecules space lost during each phase change: the ice cube gets smaller, and heavy steam seems come disappear into the air. However, in each of these three stages, the water molecules remain the same. And if you were to cool down the vapor, it would certainly reform into water. Cool it down enough, and also it would turn ago into ice. There would certainly be the very same amount the hydrogen and oxygen atom in the ice cream cube as there were in the steam, and these atoms will continue to be in the same molecular form in every stages.

Let"s take it a closer look in ~ what"s happening on a molecule level. Vapor is comprised of H20 as with the ice cube. The just difference in between vapor and ice is the the individual molecules have spread apart in vapor as result of the applications of heat. Meanwhile, in ice, the molecules team closer together since of the absence of heat. Though these phase changes require power to it is in expelled (exothermic reactions) or used (endothermic reactions), the variety of atoms and also the form of the molecule in the substance continues to be the same. That"s what makes it a physics change!

Example 2: changes in Size and Shape


Like we pointed out earlier, physical transforms are all about whether molecules stay the very same or not. When an item undergoes a physics change, it can come to be a various size and shape as lengthy as its composition continues to be the same.

Here"s what we mean: if friend have ever before dropped a item of glass on the floor, you understand that it will certainly break apart, exploding right into a million pieces. If you really wanted to, as soon as you swept all the glass up right into your dustpan, you might probably fit it all back together (even though it would certainly take a lot of time and also patience). This is also a physics reaction due to the fact that the glass continues to be glass. Once it shatters, the glass alters size and shape, but its molecule don"t change.

This is a physical adjust that only entails a readjust in size and shape. While power helped shatter the glass right into pieces, no power was supplied to rearrange the molecules.

Example 3: mixture & Solutions

Imagine you space on a day the end at the beach. The sunlight is shining, the sand is warm, and also the seagulls room trying come steal people"s lunches. After playing in the waves for a bit, you decision to make a sandcastle. Friend fill your bucket up through sand and plop that upside down. The sand comes out but it doesn"t rod together. You forgot to add water! You try again, this time v water and also voila, you"ve developed your an initial tower prefer a master sandcastle architect.

But why didn"t the sand stick with each other the first time? It needs to do v a physics property dubbed surface tension. Surface tension refers to how solid the link is in between a substance"s molecules. Water has a strong surface tension, so including it to the sand create a solid enough bond for the sand come cling together instead of falling apart.

What renders this different from a chemical reaction is the the sand and the water, though blended together, execute not change their molecule structure. The water remains water and also the sand remains sand. And if you to be to measure the water the will eventually evaporate as soon as the sandcastle dries, friend will uncover that the lot of evaporated water is equal to the amount of liquid water you included to the sand originally.

This is referred to as a mixture due to the fact that both building material (the sand and also the water) maintain their very own physical properties.

The same is true if you include salt or sugar to water. The seems favor the salt and also sugar dissolve and type new molecules. But if you to be to wait for the water to evaporate, girlfriend would discover that the salt or sugar molecules gain left behind in the glass. This is called a solution.

Solutions different from mixture in the they are homogenous. A solitary drop of saltwater would have actually the same number of salt molecule (NaCl) every water molecules (H2O) as one more drop taken from the exact same solution. In a mixture, you might have more sand than water in two various handfuls, also if they to be taken from the exact same bucket.

These physical change examples should help you recognize the difference in between a physical and also chemical change. Specifically when you to 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 chemical changes an outcome in one thing transforming into another. whether it"s a glass breaking or burning a piece of paper, the original item i do not care something different.

So how have the right to you phone call the difference in between a physical and a chemistry change? It every comes under to--you guessed it!--the molecules. In a physics change, the molecule stay specifically the exact same throughout the transformation. In a chemical change, however, it"s the molecule themselves the transform!

Here room three instances of chemical transforms to aid 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 also light) is caused by the break of molecule bonds. As a result, the initial substances transform right into entirely various substances due to the fact that of the rearrangement that molecules, i beg your pardon is an instance of a chemical change!

For instance, if you mix oxygen (O2) through a kind of hydrocarbon referred to as methane (CH4), the molecule bonds that both substances are broken, which create the heat and light. The bonds climate reform to produce two various molecules: carbon dioxide (CO2) and also water (H2O).

Combustion reaction can take place at various rates, too. An instance of a sluggish reaction is a complement burning. A fast reaction would certainly be gunpowder exploding. The amount of energy released in any combustion reaction depends on how much energy is needed to rest the molecule bonds. The harder it is to rest the bonds, the an ext energy is exit overall. However regardless of even if it is the reaction is fast or slow, burning is a chemistry change.

Example 2: Decomposition

Decomposition is rather straightforward. A decomposition reaction is a reaction in which a compound division down right into two or much more simpler substances.

For instance, once an electric existing is passed with water (H2O), it have the right to be broken down into hydrogen and oxygen or H2 + O2. In this example, water is broken down into its 2 elements. The result is a chemical change because the starting and ending molecules space different.

You"ll notice that this chemical reaction needed electrical power to happen. Decomposition reaction usually require the applications of warmth from an external source, making the an endothermic reaction.

Keep in mind that no all decomposition reactions have to malfunction into their elemental forms. More complex substances with much longer molecular chains may break down into smaller sized compounds rather of elements. An instance of this is when 2Fe(OH)3 (also known as ferric oxide) is exposed come heat. Instead of breaking right into its separation, personal, instance molecules, the turns into two compounds: Fe2O3 + 3H2O.

Example 3: Combination

Combination reactions, additionally called synthetic reactions, space the the contrary of decomposition reactions. This reactions happen when two building material (called reactants) are added together to develop one new substance. And also because this is a chemistry reaction, the result is a molecule change!

One example of this would be a pond rusting. If this might seem favor a decomposition reaction since it seems favor the pond is decomposing and falling apart. Yet actually, it"s a chemical change! stole (Fe) and also oxygen (O) combine to create the link iron oxide (Fe2O3), i beg your pardon is rust. And as you deserve to see, it additionally results in a totally new molecule.


What"s Next?

Understanding chemical and physical reactions in only one component of what you require to understand in order to succeed on the AP Chemistry Exam. We"ve gathered with each other the most vital AP Chem topics into this ultimate guide.

Taking IB Chemistry instead? Here"s the complete IB Chemistry syllabus, a an extensive study guide, and some examples of past documents from the IB Chemistry exam.

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