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, primarily carbon dioxide and water. The characteristics that enable us to distinguish one substance from another are called properties.
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.
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. 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. 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.
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Login processing Chapter 1: Introduction: Matter and Measurement. Physical properties, such as hardness and boiling point, and physical changes, such as melting or freezing, do not involve a change in the composition of matter. Chemical properties, such flammability and acidity, and chemical changes, such as rusting, involve production of matter that differs from that present beforehand.
Measurable properties fall into one of two categories. Extensive properties depend on the amount of matter present, for example, the mass of gold. Intensive properties do not depend on the amount of matter present, for example, the density of gold. Heat is an example of an extensive property, and temperature is an example of an intensive property.
Fluorine is a pale yellow gas that reacts with most substances. Finely divided metals burn in fluorine with a bright flame. Nineteen grams of fluorine will react with 1. Considering that mass and volume are both extensive properties, explain why their ratio, density, is intensive. The value of an extensive property depends upon the amount of matter being considered, whereas the value of an intensive property is the same regardless of the amount of matter being considered.
Being extensive properties, both mass and volume are directly proportional to the amount of substance under study. All Rights Reserved. Skip to content Learning Objectives By the end of this section, you will be able to: Identify properties of and changes in matter as physical or chemical Identify properties of matter as extensive or intensive. Hazard Diamond You may have seen the symbol shown in Figure 4 on containers of chemicals in a laboratory or workplace.
Chemistry End of Chapter Exercises Classify the six underlined properties in the following paragraph as chemical or physical: Fluorine is a pale yellow gas that reacts with most substances. Classify each of the following changes as physical or chemical: a condensation of steam b burning of gasoline c souring of milk d dissolving of sugar in water e melting of gold Classify each of the following changes as physical or chemical: a coal burning b ice melting c mixing chocolate syrup with milk d explosion of a firecracker e magnetizing of a screwdriver The volume of a sample of oxygen gas changed from 10 mL to 11 mL as the temperature changed.
Is this a chemical or physical change? Does oxygen undergo a chemical or physical change? Explain the difference between extensive properties and intensive properties. Identify the following properties as either extensive or intensive. Glossary chemical change change producing a different kind of matter from the original kind of matter chemical property behavior that is related to the change of one kind of matter into another kind of matter extensive property property of a substance that depends on the amount of the substance intensive property property of a substance that is independent of the amount of the substance physical change change in the state or properties of matter that does not involve a change in its chemical composition physical property characteristic of matter that is not associated with any change in its chemical composition.
Previous: 1. Next: 1. Chemical properties can be used to classify compounds and find applications for them. Understanding a material's chemical properties helps in its purification, separation from other chemicals, or identification in an unknown sample. While a chemical property is revealed only by the behavior of a substance in a chemical reaction, a physical property can be observed and measured without changing the composition of a sample. Physical properties include color, pressure, length, and concentration.
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