# data[].attributes.attachment_link.readable_text
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

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.

# data[].attributes.attachment_link.title
What Are Examples of Chemical and Physical Changes?

# data[].attributes.attachment_link.description
Here are some examples of physical changes and chemical changes, along with an explanation of how you can tell the two apart.

# data[].attributes.attachment_link.readable_text
It is important to understand the difference between chemical and physical changes. Some changes are obvious, but there are some basic ideas you should know. Physical changes are usually about physical states of matter. Chemical changes happen on a molecular level when you have two or more molecules that interact. Chemical changes happen when atomic bonds are broken or created during chemical reactions.

When you step on a can and crush it, you have forced a physical change. However, you only changed the shape of the can. It wasn't a change in the state of matter because the energy in the can did not change. Also, since this was a physical change, the molecules in the can are still the same molecules. No chemical bonds were created or broken.

When you melt an ice cube (H ₂O), you have a physical change because you add energy. You added enough energy to create a phase change from solid to liquid. Physical actions, such as changing temperature or pressure, can cause physical changes. No chemical changes took place when you melted the ice. The water molecules are still water molecules.

Chemical changes happen on a much smaller scale. While some experiments show obvious chemical changes, such as a color change, most chemical changes are not visible. The chemical change as hydrogen peroxide (H ₂O ₂) becomes water cannot be seen since both liquids are clear. However, behind the scenes, billions of chemical bonds are being created and destroyed. In this example, you may see bubbles of oxygen (O ₂) gas. Those bubbles are evidence of the chemical changes.

Melting a sugar cube is a physical change because the substance is still sugar. Burning a sugar cube is a chemical change. Fire activates a chemical reaction between sugar and oxygen. The oxygen in the air reacts with the sugar and the chemical bonds are broken.

Iron (Fe) rusts when it is exposed to oxygen gas in the air. You can watch the process happen over a long period of time. The molecules change their structure as the iron is oxidized, eventually becoming iron oxide (Fe ₂O ₃). Rusty pipes in abandoned buildings are real world examples of the oxidation process.

Some chemical changes are extremely small and happen over a series of steps. The resulting compounds might have the same number of atoms, but they will have a different structure or combination of atoms.

The sugars glucose, galactose, and fructose all have six carbon atoms, twelve hydrogen atoms, and six oxygen atoms (C ₆H ₁₂O ₆). Even though they are made of the same atoms, they have very different shapes and are called isomers. Isomers have atoms bonded in different orders.

Each of the sugars goes through different chemical reactions because of the differences in their molecular structure. Scientists say that the arrangement of atoms allows for a high degree of specificity, especially in the molecules of living things. Specificity means the molecules will only work in specific reactions, not all of them. For example, your body uses glucose as an energy source. If you eat galactose molecules, they need to be converted into glucose before your body can use them.

# data[].attributes.attachment_link.title
Chem4Kids.com: Matter: Chemical vs. Physical Changes

# data[].attributes.attachment_link.description
It is important to understand the difference between chemical and physical changes. Some changes are obvious, but there are some basic ideas you should know. Physical changes are usually about physical states of matter. Chemical changes happen on a molecular level when you have two or more molecules that interact.

# data[].attributes.attachment_link.description
Kid's learn about the science of states of matter. Solids, liquids, gases, and even plasma.

# data[].attributes.attachment_link.description
Free gamified quizzes on every subject that students play in class and at home. Pick an existing quiz or create your own for review, formative assessment, and more.

# data[].attributes.attachment_link.title
Scholastic Teaching Tools | Resources for Teachers

# data[].attributes.attachment_link.description
Explore Scholastic Teaching Tools for teaching resources, printables, book lists, and more. Enhance your classroom experience with expert advice!