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 , and food being cooked, digested, or rotting Figure 3.
Figure 3. Properties of matter fall into one of two categories. If the property depends on the amount of matter present, it is an extensive property. The mass and volume of a substance are examples of extensive properties; for instance, a gallon of milk has a larger mass and volume than a cup of milk. The value of an extensive property is directly proportional to the amount of matter in question. If the property of a sample of matter does not depend on the amount of matter present, it is an intensive property.
Temperature is an example of an intensive property. As another example, consider the distinct but related properties of heat and temperature. A drop of hot cooking oil spattered on your arm causes brief, minor discomfort, whereas a pot of hot oil yields severe burns. Both the drop and the pot of oil are at the same temperature an intensive property , but the pot clearly contains much more heat extensive property. You may have seen the symbol shown in Figure 4 on containers of chemicals in a laboratory or workplace.
Figure 4. The system details flammability, reactivity, health, and other hazards. 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. Notice that corn oil has a lower mass to volume ratio than water.
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.
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. Chemical properties of matter describe its potential to undergo some chemical change or reaction by virtue of its composition.
Think of it as the ability to stretch a given metal into a wire. Ductility is often measured using a tensile test as a percentage of elongation, or the reduction in the cross sectional area of the sample before failure.
The tendency of a material to resist cracking or breaking under stress makes ductile materials appropriate for other metalworking processes including rolling or drawing. Certain other processes like cold-working tend to make a metal less ductile. Pressure, or compressive stress, is used to press or roll the material into thinner sheets. A material with high malleability will be able to withstand higher pressure without breaking.
As opposed to materials that exhibit plasticity where the change in shape is not reversible , an elastic material will return to its previous configuration when the stress is removed. The higher the Modulus — meaning greater stress results in proportionally lesser deformation — the stiffer the material.
This is an important design consideration for applications where stiffness is required under load. The effect of impact — a collision that occurs in a short period of time — is typically greater than the effect of a weaker force delivered over a longer period. So a consideration of impact resistance should be included when the application includes an elevated risk of impact. Certain metals may perform acceptably under static load but fail under dynamic loads or when subjected to a collision.
In the lab, impact is often measured through a common Charpy test, where a weighted pendulum strikes a sample opposite of machined V-notch. Typically, the harder the material, the better it resists wear or deformation. The term hardness, thus, also refers to local surface stiffness of a material or its resistance to scratching, abrasion, or cutting. Hardness is measured by employing such methods as Brinell, Rockwell, and Vickers, which measure the depth and area of a depression by a harder material, including a steel ball, diamond, or other indenter.
Plasticity, the converse of elasticity, describes the tendency of a certain solid material to hold its new shape when subjected to forming forces. It is the quality that allows materials to be bent or worked into a permanent new shape.
Materials transition from elastic behavior to plastic at the yield point. Fatigue can lead to fracture under repeated or fluctuating stresses for example loading or unloading that have a maximum value less than the tensile strength of the material. Higher stresses will accelerate the time to failure, and vice versa, so there is a relationship between the stress and cycles to failure. Use the link below to answer the following questions:. Skip to main content.
Matter and Change. Search for:. Physical Properties Learning Objectives Define physical property. List and describe physical properties of matter. Why are drag car standards constantly reinforced? Figure 1. Figure 2. Diamond ring. Summary A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance.
Physical properties include color, density, hardness, and melting and boiling points. Give an example of malleability. Define ductility. Review What is a physical property?
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