While many elements differ dramatically in their chemical and physical properties, some elements have similar properties. Each hazard is rated on a scale from 0 to 4, with 0 being no hazard and 4 being extremely hazardous. The white (bottom) diamond points out special hazards, such as if it is an oxidizer (which allows the substance to burn in the absence of air/oxygen), undergoes an unusual or dangerous reaction with water, is corrosive, acidic, alkaline, a biological hazard, radioactive, and so on. The yellow (right) diamond describes reactivity hazards, such as how readily the substance will undergo detonation or a violent chemical change. The blue (left) diamond indicates the level of health hazard. Within the overall diamond symbol, the top (red) diamond specifies the level of fire hazard (temperature range for flash point). The system details flammability, reactivity, health, and other hazards. The National Fire Protection Agency (NFPA) 704 Hazard Identification System was developed by NFPA to provide safety information about certain substances. 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).įigure 1.21 The National Fire Protection Agency (NFPA) hazard diamond summarizes the major hazards of a chemical substance. A drop of hot cooking oil spattered on your arm causes brief, minor discomfort, whereas a pot of hot oil yields severe burns. As another example, consider the distinct but related properties of heat and temperature. If the gallon and cup of milk are each at 20 ☌ (room temperature), when they are combined, the temperature remains at 20 ☌.

Temperature is an example of an intensive property.

If the property of a sample of matter does not depend on the amount of matter present, it is an intensive property. The value of an extensive property is directly proportional to the amount of matter in question. The mass and volume of a substance are examples of extensive properties for instance, a gallon of milk has a larger mass than a cup of milk. If the property depends on the amount of matter present, it is an extensive property. Properties of matter fall into one of two categories.

(credit b: modification of work by Jeff Turner credit c: modification of work by Gloria Cabada-Leman credit d: modification of work by Roberto Verzo) (d) A banana turning brown is a chemical change as new, darker (and less tasty) substances form. (c) Cooking red meat causes a number of chemical changes, including the oxidation of iron in myoglobin that results in the familiar red-to-brown color change. (b) During the combustion of a match, cellulose in the match and oxygen from the air undergo a chemical change to form carbon dioxide and water vapor. 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.įigure 1.20 (a) Copper and nitric acid undergo a chemical change to form copper nitrate and brown, gaseous nitrogen dioxide. Other examples of physical changes include magnetizing and demagnetizing metals (as is done with common antitheft security tags) and grinding solids into powders (which can sometimes yield noticeable changes in color). Physical changes are observed when wax melts, when sugar dissolves in coffee, and when steam condenses into liquid water ( Figure 1.18). A physical change is a change in the state or properties of matter without any accompanying change in the chemical identities of the substances contained in the matter. Other physical properties, such as the melting temperature of iron or the freezing temperature of water, can only be observed as matter undergoes a physical change. Some physical properties, such as density and color, may be observed without changing the physical state of the matter. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity. A physical property is a characteristic of matter that is not associated with a change in its chemical composition. The characteristics that distinguish one substance from another are called properties. Identify properties of matter as extensive or intensive.Identify properties of and changes in matter as physical or chemical.By the end of this section, you will be able to:

Examples of physical changes