All matter has physical and historicsweetsballroom.comical properties. Physical properties are characteristics that scientists can measure without changing the composition of the sample under study, such as mass, color, and volume (the amount of space occupied by a sample). historicsweetsballroom.comical properties describe the characteristic ability of a substance to react to form new substances; they include its flammability and susceptibility to corrosion. All samples of a pure substance have the same historicsweetsballroom.comical and physical properties. For example, pure copper is always a reddish-brown solid (a physical property) and always dissolves in dilute nitric acid to produce a blue solution and a brown gas (a historicsweetsballroom.comical property).

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Physical Property

A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Silver is a shiny metal that conducts electricity very well. It can be molded into thin sheets, a property called malleability. Salt is dull and brittle and conducts electricity when it has been dissolved into water, which it does quite easily. Physical properties of matter include color, hardness, malleability, solubility, electrical conductivity, density, melting point, and boiling point.

For the elements, color does not vary much from one element to the next. The vast majority of elements are colorless, silver, or gray. Some elements do have distinctive colors: sulfur and chlorine are yellow, copper is (of course) copper-colored, and elemental bromine is red. However, density can be a very useful parameter for identifying an element. Of the materials that exist as solids at room temperature, iodine has a very low density compared to zinc, chromium, and tin. Gold has a very high density, as does platinum. Pure water, for example, has a density of 0.998 g/cm3 at 25°C. The average densities of some common substances are in Table \(\PageIndex{1}\). Notice that corn oil has a lower mass to volume ratio than water. This means that when added to water, corn oil will “float.”

Table \(\PageIndex{1}\): Densities of Common Substances SubstanceDensity at 25°C (g/cm3)
blood 1.035
body fat 0.918
whole milk 1.030
corn oil 0.922
mayonnaise 0.910
honey 1.420

Hardness helps determine how an element (especially a metal) might be used. Many elements are fairly soft (silver and gold, for example) while others (such as titanium, tungsten, and chromium) are much harder. Carbon is an interesting example of hardness. In graphite, (the "lead" found in pencils) the carbon is very soft, while the carbon in a diamond is roughly seven times as hard.

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Figure \(\PageIndex{1}\): Pencil (left) and Diamond ring (right). Both are a form of carbon, but exhibit very different physical properties.

Melting and boiling points are somewhat unique identifiers, especially of compounds. In addition to giving some idea as to the identity of the compound, important information can be obtained about the purity of the material.



historicsweetsballroom.comical Properties

historicsweetsballroom.comical properties of matter describeits potentialto undergo some historicsweetsballroom.comical change or reaction by virtue of its composition. Theelements, electrons, and bonds thatare present give the matter potential for historicsweetsballroom.comical change. It is quite difficult to define a historicsweetsballroom.comical property without using the word "change". Eventually, after studying historicsweetsballroom.comistry for some time,you should be able to look at the formula of a compound and state some historicsweetsballroom.comical property. For example, hydrogen has the potential to ignite and explode given the right conditions—this is a historicsweetsballroom.comical property. Metals in general have thehistoricsweetsballroom.comical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas—this is a historicsweetsballroom.comical property.

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Figure \(\PageIndex{2}\): Heavy rust on the links of a chain near the Golden Gate Bridge in San Francisco; it was continuously exposed to moisture and salt spray, causing surface breakdown, cracking, and flaking of the metal. (CC BY-SA 3.0; Marlith).

A historicsweetsballroom.comical property of iron is its capability of combining with oxygen to form iron oxide, the historicsweetsballroom.comical name of rust (Figure \(\PageIndex{2}\)). The more general term for rusting and other similar processes is corrosion. Other terms that are commonly used in descriptions of historicsweetsballroom.comical changes are burn, rot, explode, decompose, and ferment. historicsweetsballroom.comical properties are very useful in identifying substances. However, unlike physical properties, historicsweetsballroom.comical properties can only be observed as the substance is in the process of being changed into a different substance.

Table \(\PageIndex{2}\): Contrasting Physical and historicsweetsballroom.comical Properties Physical Propertieshistoricsweetsballroom.comical Properties
Gallium metal melts at 30 oC. Iron metal rusts.
Mercury is a very dense liquid. A green banana turns yellow when it ripens.
Gold is shiny.

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A dry piece of paper burns.


Exercise \(\PageIndex{1B}\)