Name: distinguishing physical and chemical changes
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 2 min 57 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.1

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Physical and Chemical Properties of Matter

Characteristics that help us to distinguish one type of matter from another are referred to as properties. Matter exhibits two types of properties: physical and chemical.

Physical properties of matter can be measured and observed without changing the composition or identity of the matter. Odor, taste, color, appearance, hardness, density, melting and boiling points, and electrical conductivity, are all examples of physical properties.

Some of these physical properties can be observed without changing the physical state of the matter. So, when we say that helium gas is lighter than air, we are referring to a physical property. Similarly, the smell of gasoline is also a physical property.

Other physical properties can only be observed when matter undergoes physical changes. For example, pure gold in its solid-state is made up of tightly packed gold atoms. But when it is melted at a high temperature, it changes its state from a solid to a liquid. However, this liquid is still composed of gold atoms, so this is a physical change.

Similarly, when liquid water freezes to solid ice, the chemical composition of both the water and ice remains the same. Thus, physical changes only alter the state of the matter or physical conditions, without changing the chemical composition.

Crushing, grinding, slicing, blending, magnetizing, or demagnetizing are other common ways to change the physical condition of matter.&nbsp;

Chemical properties of matter, on the other hand, are characteristics that can only be measured and observed when the substance has a change in chemical composition. Corrosiveness, flammability, toxicity, acidity, or chemical reactivity are all examples of chemical properties of matter.

In order to identify a chemical property, we look for a chemical change. Chemical changes involve chemical reactions and are often observed through a change in color or odor.

For example, when a copper penny is exposed to air and water there is a chemical change. The copper undergoes a series of chemical reactions, one of which is shown here, to form a layer of blue-green patina on an otherwise naturally brown penny.

Thus, chemical changes produce entirely new forms of matter which differ from the matter present before the change. For instance, the flammability of gasoline is a chemical property evident from the chemical changes in the composition of gasoline when it burns, turning gasoline into entirely new substances,&nbsp;primarily carbon dioxide and water.&nbsp;

physical and chemical properties of matter

The characteristics that enable us to distinguish one substance from another are called properties.

<h4>Physical Properties of Matter</h4>

A physical property is a characteristic of matter that is not associated with a change in its chemical composition. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity. We can observe some physical properties, such as density and color, without changing the physical state of the matter observed. Other physical properties, such as the melting temperature of iron or the freezing temperature of the water, can only be observed as matter undergoes a physical change.&nbsp;

A physical change is a change in the state or properties of matter without any accompanying change in its chemical composition (the identities of the substances contained in the matter). We observe a physical change when, for example, wax melts, sugar dissolves in coffee, and steam condenses into liquid water. Other examples of physical changes include magnetizing and demagnetizing metals (as is done with common anti-theft security tags) and grinding solids into powders. In each of these examples, there is a change in the physical state, form, or properties of the substance, but no change in its chemical composition.

<h4>Chemical Properties of Matter</h4>

The change of one type of matter into another type (or the inability to change) is a chemical property. Examples of chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion. Iron, for example, combines with oxygen in the presence of water to form rust; chromium does not oxidize. Nitroglycerin is very dangerous because it explodes easily; neon poses almost no hazard because it is very unreactive.&nbsp;

To identify a chemical property, we look for a chemical change. A chemical change always produces one or more types of matter that differ from the matter present before the change. The formation of rust is a chemical change because rust is a different kind of matter than the iron, oxygen, and water present before the rust formed. The explosion of nitroglycerin is a chemical change because the gases produced are very different kinds of matter from the original substance. Other examples of chemical changes include reactions that are performed in a lab (such as copper reacting with nitric acid), all forms of combustion (burning), the ripening of fruits, and food being cooked, digested, or rotting.&nbsp;

This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/1-3-physical-and-chemical-properties">Openstax, Chemistry 2e, Section 1.3: Physical and Chemical Properties.</a>

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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Introduction: Matter and Measurement

KEY TERMS AND CONCEPTS

distinguishing physical and chemical changes

Matter can be identified by its properties, which are the features that help us tell one substance from another. These properties fall into two main groups: physical properties and chemical properties. Understanding the difference helps explain how matter changes.

A physical property is a feature of matter that is not linked to a change in chemical composition. Examples include density, color, hardness, melting point, boiling point, and electrical conductivity. Some physical properties can be observed without changing the state of the matter, such as density and color. Others appear only during a physical change, like the melting temperature of iron or the freezing temperature of water.

A physical change alters the state or form of matter without changing what the substance is made of. Wax melting, sugar dissolving in coffee, and steam condensing into liquid water are all physical changes. Magnetizing and demagnetizing metals, such as in anti-theft security tags, and grinding solids into powders are also physical changes. In each case, the material looks or behaves differently, but its chemical composition stays the same.

Chemical properties describe whether matter can change into a different type of matter, or resist that change. Common chemical properties include flammability, toxicity, acidity, reactivity, and heat of combustion. Iron reacts with oxygen and water to form rust, while chromium does not oxidize. Nitroglycerin explodes easily, but neon is very unreactive.

To identify a chemical property, we look for a chemical change. A chemical change produces one or more new kinds of matter that are different from the starting material. Rust formation is a chemical change because rust is not the same as iron, oxygen, or water. Nitroglycerin exploding is also a chemical change because the gases produced are different from the original substance. Other chemical changes include copper reacting with nitric acid, burning, fruit ripening, and food being cooked, digested, or rotting.

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Distinguishing Physical and Chemical Changes

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