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Chemical and Physical Changes of Matter
If you are confused about chemical and physical changes and how to tell them apart, you’ve come to the right place. Chemical and physical changes both are changes in the structure of matter . In a chemical change , a chemical reaction occurs and a new substance is produced. In a physical change , matter changes forms but does not change its chemical identity. So, the difference between chemical and physical changes is that a chemical change alters the chemical composition of matter, while a physical change does not
A chemical change produces a new substance, while a physical change alters the form of matter but not its chemical identity.
Chemical Changes
A chemical change involves a chemical reaction to produce a new product . It is a change at the molecular level of matter. Chemical bonds between atoms break and then form to connect different atoms.
Examples of Chemical Changes
In a chemical change, new product forms as atoms rearrange themselves. Chemical bonds are broken and reform to make new molecules. Examples of chemical changes include:
- Souring milk
- Digesting food
- Cooking an egg
- Baking a cake
- Rusting iron
- Mixing an acid and a base
- Burning a candle
- Mixing baking soda and vinegar
Physical Changes
A physical change is a change in matter that alters its form but not its chemical identity. The size or shape of matter often changes, but there is no chemical reaction. Phase changes are physical changes. These include melting, boiling, vaporization, freezing, sublimation and deposition. Breaking, crumpling, or molding matter also results in a physical change. Many physical changes are reversible.
- Examples of Physical Changes
Examples of physical changes include:
- Melting an ice cube
- Freezing an egg
- Boiling water
- Sublimation of dry ice into carbon dioxide gas
- Shredding paper
- Crushing a can
- Breaking a bottle
- Chopping vegetables
- Mixing sand and salt
- Making sugar crystals
- Dissolving sugar in water (the sugar mixes with the water, but can be recovered by evaporation or boiling)
How to Tell Chemical and Physical Changes Apart
The key to distinguishing between chemical and physical changes is determining whether there is a new substance that wasn’t there before. If you see signs of a chemical reaction, it’s probably a chemical change. Signs of a reaction include:
- Temperature change
- Color change
- Formation of a precipitate
If none of these signs are present, it’s a good bet a physical change occurred.
Are Physical Changes Reversible?
Some people use reversibility as a test for chemical and physical changes. The premise is that a physical change can be undone, while a chemical change can only be reversed by another chemical reaction. This is not a great test because there are too many exceptions. While you can melt and freeze an ice cube (a physical change), it’s much harder to reassemble shredded paper (another physical change).
Most physical changes can be reversed if energy is added. Some chemical changes are reversible, but only via another chemical reaction. For example, rusting of iron is a chemical change. Converting rust back into iron and oxygen is possible, but it requires a chemical reaction.
Practice Identifying Chemical and Physical Changes
Download and print this worksheet for practicing identifying chemical and physical changes. The worksheet and answer key are PDF files, or you can right-click, save, and print the PNG image.
[ PDF Worksheet ] [ Answer Key ]
Explore chemical and physical changes in greater detail and learn how they relate to chemical and physical properties of matter:
- Examples of Chemical Properties
- Is Dissolving Salt a Chemical or Physical Change?
- Examples of Physical Properties
- Atkins, P.W.; Overton, T.; Rourke, J.; Weller, M.; Armstrong, F. (2006). Shriver and Atkins Inorganic Chemistry (4th ed.). Oxford University Press. ISBN 0-19-926463-5.
- Chang, Raymond (1998). Chemistry (6th ed.). Boston: James M. Smith. ISBN 0-07-115221-0.
- Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0.
- Kean, Sam (2010). The Disappearing Spoon – And Other True Tales From the Periodic Table . Black Swan, London. ISBN 978-0-552-77750-6.
- Zumdahl, Steven S.; Zumdahl, Susan A. (2000). Chemistry (5th ed.). Houghton Mifflin. ISBN 0-395-98583-8.
Related Posts
Changes in Matter: Physical vs. Chemical Changes
Physical changes do not produce a new substance. Chemical changes result in the production of a new substance and cannot be reversed.
Oxidized Copper Lion
The process of rusting, or oxidization, exemplifies a chemical reaction. Here is an oxidized copper lion statute in front of the Chicago Art Institute and the Aon Center.
Photograph by Paul Damien
Matter is anything that has mass and takes up space. The tiny particles called atoms are the basic building blocks of all matter. Atoms can be combined with other atoms to form molecules . Matter is capable of undergoing changes, which are classified as either physical or chemical. Physical changes in matter are often reversible. For example, an ice cube can melt into liquid water, and then the liquid water can be refrozen into an ice cube. A chemical change is very different. A burning log demonstrates this. The log turns to ashes. However, its ashes cannot be changed back into a log. The burning was a chemical change. Unlike many physical changes, it cannot be easily reversed. What Is a Physical Change? In a physical change, the structure of the changed material remains the same before and after the change. Physical changes may affect the texture, shape, and temperature of a substance. They can also affect the material's state of matter. A change in the texture of a substance is a change in the way it feels. For example, a block of wood may feel rough when you run your finger across it. Rubbing the wood with sandpaper smooths the surface, so it no longer feels rough. This is an example of a physical change: The texture of the wood has changed, but the wood's molecular structure has not. A physical change may also involve a change of phase between solid, liquid, and gas. When a material changes phase, it only changes physically; the substance is still the same, even though its form is different. Think about ice melting into water. It can then be heated up and turned into steam. The phase changes, but the structure of water does not. The water molecules are still water molecules, whether the water is in liquid form, in solid form as ice, or in gas form as steam. What Is a Chemical Change? Chemical changes are very different from physical changes. A chemical change takes place when the composit ion of a substance is altered. This requires the breaking and forming of chemical bonds during a reaction. Chemical bonds hold molecules together. A chemical change results in the rearranging of atoms in substances. This rearrangement leads to the creation of brand new molecules. The new molecules are the products of the chemical reaction . They cannot be easily reverted back to their original state. Sometimes it is not easy to tell whether a chemical reaction has taken place. To figure it out, scientists look for a few basic signs. Indicators of a chemical change can include a change in temperature, color, or odor. In a chemical change, temperature may rise or fall. This release of heat is the result of the breaking or formation of chemical bonds. Burning wood is an example of a reaction that releases energy as heat. The opposite may also indicate a chemical reaction. A chemical change can cause heat to be absorbed. The result is a decrease in temperature. A chemical cold pack in a first aid kit demonstrates this kind of chemical reaction. It absorbs heat energy, which results in cooling. A color change can also signal a chemical reaction. A common example can be observed when you leave an iron nail outside. The iron reacts with oxygen in the air. The reaction produces iron oxide. As a result, the nail develops a reddish-brown rust. The odor of rotting food also indicates a chemical change. The food undergoes chemical reactions as it begins to break down. These changes lead to the formation of new substances. These substances produce unique, often, unpleasant smells. Another sign of a chemical reaction may be the formation of a precipitate . When certain chemicals are mixed together in a solution, a new solid can form in the liquid mixture. This solid is a precipitate. It shows that a chemical reaction has taken place. The change has altered the original substances. A chemical reaction may also release a gas. For example, a mixture of vinegar and baking soda will immediately start bubbling and foaming. The bubbles are a release of carbon dioxide gas, a product of the chemical reaction between the two common substances. Chemical Change or Physical Change? Sometimes it is difficult to tell whether a change is physical or chemical. The formation of alloys is one example. An alloy is a metal made from a mixture of other metals. The alloy's properties are different from the properties of the metals used to make it. Brass is a common example of an alloy. It's used to make musical instruments including trumpets and trombones. Brass is made up of about 60 percent copper and 40 percent zinc. It has different properties than either copper or zinc alone. Yet it is not the result of chemical reaction. That may seem confusing, because brass is different from both copper and zinc. However, though the copper and zinc atoms are both present in brass, they do not chemically bond together. No chemical bonds are formed or broken. As a result, the creation of brass represents a physical change, not a chemical one.
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Examples of Physical Changes and Chemical Changes
What Are Physical and Chemical Changes?
ThoughtCo / Hilary Allison
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Are you confused about the difference between chemical changes and physical changes and how to tell them apart? In a nutshell, a chemical change produces a new substance , while a physical change does not. A material may change shapes or forms while undergoing a physical change, but no chemical reactions occur, and no new compounds are produced.
There are also other indications of chemical and physical changes, such as odor and sound. Here is a look at how to recognize the two types of changes, along with telltale indications and common examples of each.
Key Takeaways
- A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.
- Examples of chemical changes are burning, cooking, rusting, and rotting.
- Examples of physical changes are boiling, melting, freezing, and shredding.
- Many physical changes are reversible if sufficient energy is supplied, but the only way to reverse a chemical change is via another chemical reaction.
Examples of Chemical Changes
A new compound (product) results from a chemical change as the atoms rearrange themselves to form new chemical bonds. A chemical change always involves a chemical reaction. The starting materials and final product are chemically different from one another. Here are some examples of chemical changes:
- Burning wood
- Souring milk
- Mixing acid and a base
- Digesting food
- Cooking an egg
- Heating sugar to form caramel
- Baking a cake
- Rusting of iron
- Examples of Physical Changes
No new chemical species forms in a physical change. Changing the state of a pure substance between the solid, liquid, or gas phase is a physical change since the identity of the matter does not change. A physical change involves changes in physical properties, but not chemical properties. For example, physical properties change during tempering steel, crystallization, and melting. Here are examples of physical changes:
- Crumpling a sheet of aluminum foil
- Melting an ice cube
- Casting silver in a mold
- Breaking a bottle
- Boiling water
- Evaporating alcohol
- Shredding paper
- Sublimation of dry ice into carbon dioxide vapor
- Carbon changing from graphite into a diamond
How to Tell Physical and Chemical Changes Apart
Look for an indication that a chemical change occurred. Signs of a chemical change include the following:
- Gas is produced. In liquids, bubbles may form.
- An odor is produced.
- The substance changes color.
- Sound is produced.
- There is a temperature change. The surroundings become either hot or cold.
- Light is produced.
- A precipitate forms.
- The change is difficult or possible to reverse.
A chemical change might not display all of these signs. If you don't see any of these indications, a physical change likely occurred. Be aware a physical change may produce a dramatic change in the appearance of a substance. This doesn't mean a chemical reaction occurred. The only way to know for certain whether a change is chemical or physical is a chemical analysis of the starting and ending materials.
In some cases, it may be hard to tell whether a chemical or physical change occurred. For example, when you dissolve sugar in water , a physical change occurs. The form of the sugar changes, but it remains the same chemically (sucrose molecules). However, when you dissolve salt in water, the salt dissociates into its ions (from NaCl into Na + and Cl - ), so a chemical change occurs. In both cases, a white solid dissolves into a clear liquid, and in both cases, you can recover the starting material by removing the water, yet the processes are not the same.
Explore chemical and physical changes in greater detail. Learn how they relate to the chemical and physical properties of matter with these additional resources.
- More Examples of Physical Changes
- More Examples of Chemical Changes
- Chemical and Physical Properties
- Understanding Chemical and Physical Changes
- Examples of Chemical Reactions in Everyday Life
- 10 Examples of Heterogeneous and Homogeneous Mixtures
- 10 Cool Chemistry Experiments
- Physical Changes in Chemistry
- Dissolving Sugar in Water: Chemical or Physical Change?
- Understanding Chemical & Physical Changes in Matter
- Is Dissolving Salt in Water a Chemical Change or Physical Change?
- Chemical Change Examples
- Chemical Change Definition in Chemistry
- Difference Between Physical and Chemical Properties
- What Is a Chemical Reaction?
- Chemical Properties and Physical Properties
- Physical Properties of Matter
- Definition and Examples of a Product in Chemistry
- Examples of Physical Properties of Matter - Comprehensive List
Home / Essay Samples / Life / Change / Defining the Difference Between Physical and Chemical Changes
Defining the Difference Between Physical and Chemical Changes
- Category: Life , Science
- Topic: Change , Chemical Reaction , Thermodynamics
Pages: 4 (1884 words)
Views: 2593
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Introduction
Identifying a physical change, identifying a chemical change, chemical changes, physical changes, change in physical properties, improvements, application.
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