Is Flammability Considered A Chemical Or Physical Property?

Is Flammability A Chemical Or Physical Property

One of the properties an object can have is flammability.

It is important to know whether or not an object or material is flammable in order to prevent fires. But is flammability a physical or a chemical property?

If you want to know more about flammability and whether it is a chemical property or a physical property then keep reading.

We have put together this guide to tell you everything you need to know.

What Are Physical Properties?

Before we discuss flammability, it is important that you understand the difference between chemical properties and physical properties.

Properties are characteristics of substances that allow them to be distinguished from each other, and the properties relate to different things.

Physical properties are a characteristic of a substance that is not relevant to any changes in its chemical composition. For example, density and hardness are physical properties.

Whether a substance conducts electricity is also a physical property, as is the melting and boiling point of the substance.

If the physical change that you see does not change the chemical composition of the substance, then it is related to a physical property rather than a chemical one.

Physical properties can be useful for immediately identifying a substance. The color and texture can give you a good idea of what you are dealing with.

However, density is usually the best physical property to use if you want to accurately identify a substance. That is because almost every element or substance has a slightly different density.

Understanding the physical properties of different substances helps you to understand what they are capable of and what they can be used for.

For example, if you want to make a durable tool then you need to know the hardness of a substance to determine whether it is suitable.

But if you wanted to make a blanket, you would need to know the softness of a substance instead.

What Are Chemical Properties?

Changes that turn one type of substance into another by altering its chemical composition are related to chemical properties.

This could include the reactivity, toxicity, and acidity of a substance.

To identify if a chemical change has taken place, ask yourself if there is matter present that was not present before.

For example, when iron oxidizes it produces rust. The rust was not present before so the oxidation of iron is a chemical change.

A chemical reaction occurs when electrons and neutrons are shared between different substances, creating chemical bonds between the atoms.

This means that the chemical composition of one or both substances will be different.

For example, when hydrogen is burned in the presence of oxygen, the two substances bond together to form dihydrogen monoxide (water).

Sometimes, you will only be able to establish that a chemical change has taken place by analyzing the chemical composition of the substance afterwards.

For example, carbon dioxide and oxygen are not visible. If you burn oxygen to create carbon dioxide, you will not be able to see this chemical change.

You will need to chemically analyze the gas to see if it has a different chemical composition from the one you started with.

Some chemical properties will relate to a group of substances. For example, almost all metals will react when they are exposed to acid.

But there are other substances that react with acid, so you cannot use this chemical property alone to identify a metal.

How Can You Tell Chemical And Physical Changes Apart?

Sometimes it can be easy to confuse physical changes with chemical changes.

For example, you can take a big chunk of metal and turn it into thin sheets which can be manipulated into different shapes.

The metal will look different, but the chemical composition of the metal will have remained unchanged. This means it is a physical change, not a chemical change.

A trickier one is the process of dissolving sugar in water. If you dissolve the sugar in water, the sugar will no longer be visible.

This might lead you to believe that a chemical change has taken place.

However, the sugar is still present in the same chemical composition as it was before, so it is a physical change rather than a chemical one.

When sulfuric acid is added to copper, the two substances bond together to create copper sulfate. The clear acid and bronze colored metal become a blue substance.

A chemical change has taken place. It is not a physical change because the chemical composition is different. In this case, the change of color is evidence of the chemical change.

However, most chemical changes require scientific procedures and equipment to determine the chemical change that has taken place.

As long as the chemical composition of the substance remains the same, the change is classified as physical not chemical. You will not always be able to ascertain this with the naked eye.

Another way to tell physical and chemical changes apart is that physical changes tend to be a lot easier to reverse than chemical changes.

This is not a foolproof method, but it can be helpful.

Why Is Melting Point A Physical Change Not A Chemical One?

Now that you understand the difference between physical changes and chemical changes, you might still be confused about melting points.

When something melts, it appears completely different to how it was before. So surely this is a chemical change?

No - melting something is a physical change. For example, if you melt a metal it will become runny instead of solid, and it will lose its hardness.

However, the chemical composition of the metal remains the same.

If you take a sample of solid metal and melted metal and chemically analyze them, they will have the same chemical composition.

Also, the change is easily reversible. Once the metal has cooled it will become solid again, exactly the same as how it was before (except it might be a different shape).

Finding out the melting point of a substance is relatively easy. Monitor the temperature of a substance while you are applying heat to it. The temperature will gradually rise, but at some point it will maintain its level.

This is when the heat is beginning to melt the substance and turn it into a liquid, so the overall temperature of the substance stops rising temporarily. This is the melting point.

Why Is Boiling Point A Physical Change Not A Chemical One?

Why Is Boiling Point A Physical Change Not A Chemical One?

The melting point of a substance is a physical change, but what about the boiling point? Changing a substance from liquid to gas surely changes its chemical composition?

Actually, the vaporization of a substance (turning it into a gas) only changes the physical properties of the substance, not the chemical ones.

That means that boiling point is a physical property, not a chemical one. Boiling is also reversible.

If you hold a cool pan lid over the steam coming off boiling water, the steam will turn back into liquid when it hits the lid, reverting back into its previous physical state.

Water is a great substance to use if you want to witness various physical changes and their reversibility.

You can melt ice into water, vaporize the water into steam, condense the steam back into water, then freeze the water back into ice.

What Is Flammability?

If a substance is flammable, that means that it is capable of igniting or burning. This means that the substance has the potential to start a fire.

Sometimes the word combustible is used instead of flammable. They have slightly different meanings but tend to be used interchangeably.

Some items are not considered flammable. This includes glass, steel, and helium.

Flammable substances can be more or less flammable than others, but it is difficult to know exactly how flammable a substance is unless it has undergone fire testing.

Flammable items tend to be categorized into flammable or highly flammable.

It is important to know whether a substance is non-flammable, flammable or highly flammable.

The flammability of a substance will determine how it is handled, stored, transported and used. A lot of flammable or highly flammable items will be labeled to make the risk clear.

If you are going to make a flame resistant suit, then you need to know that the materials you are using are not flammable.

If you are designing an outdoor oven that will contain an open flame, then you need to make sure that you don’t include flammable materials in the design.

Similarly, if you are trying to build a fire to heat your home or to hold a bonfire event, you will need to ensure that you only use flammable materials or the fire won’t burn.

Is Flammability A Chemical Or A Physical Property?

Flammability is a chemical property. This is because the act of combustion (setting fire to something and letting it burn) changes the chemical composition of the substance.

If you set something on fire, the matter that you have at the end will be different to what you started with - this means that a chemical change has taken place.

Burning something is an irreversible chemical change. If you burn a piece of material into ash, you cannot then turn the ash back into a piece of material.

Burnt wood can be reformed into wood.

Flammability is a chemical property that applies to a lot of different substances.

Chemical Reactions Involving Flammability

You will likely witness chemical reactions that involve flammability every single day.

They are very common because there are many substances that are flammable, and combustion is used in modern life as a useful tool.

The natural gas that comes out of your gas stove has flammability as a chemical property. When the gas burns it produces carbon dioxide (and a very small amount of carbon monoxide).

The chemical composition of the gas is changed and it is almost impossible to turn these byproducts back into their original form.

That means that every time you light your stove, you are starting a chemical reaction.

If you drive a car or a vehicle of any kind, then you are also starting a chemical reaction.

The fuel that burns to power the engine is chemically changed, creating the byproducts that come out of the exhaust.

One of the reasons that fire is so destructive is that the changes it causes to chemical properties cannot be reversed.

Properties and items within them are changed beyond repair. Wildfires destroy habitats and change the chemical composition of the soil, making it hard to regrow what was destroyed.

Fire also changes the chemical composition of your skin, which is why burn injuries are so painful and difficult to treat. They can also take a long time to heal.

Is Flammability An Extensive Or Intensive Property?

Properties of substances can either be extensive or intensive. Extensive properties depend on the amount of the substance that is present - for example, mass and volume.

The mass and volume of a substance will change depending on how much of the substance that you have.

Intensive properties remain the same regardless of the amount as they are relative to the type of substance that is present, not how much of it there is.

Take, for example, water. The volume of water you have is an extensive property. You could have a teaspoon of water, a cup of water, or a whole saucepan full of water.

However, the temperature of the water is an intensive property.

If you leave a container of water out of the refrigerator for several hours, the water will be the same temperature as most of the other substances in the room, regardless of how much water there is.

On this basis, you will understand that flammability is an intensive property. A flammable substance will be flammable regardless of how much or how little of it there is.

A non-flammable substance will still be non-flammable regardless of whether there is a lot of it or a little bit of it.

A substance will burn faster if there is less of it, but a large amount will still burn. Keep in mind that while temperature is intensive, heat is extensive.

This is because the amount of heat you can absorb will depend on how much of the substance there is.

A small drop of oil can hold less heat then a big vat of oil. A small fire will generate less heat than a large blaze.


Flammability is a chemical property of a substance that determines how easy it is for that substance to catch on fire or burn.

Once a substance has been set on fire, it undergoes a chemical reaction called combustion. This reaction causes irreversible changes to the chemical composition of the substance.

It is important to understand the flammability of different substances in order to prevent fires and the extensive damage that they cause.

It is also useful to understand the differences between chemical properties and physical properties, and how to tell the difference between chemical changes and physical changes.