For example, hydrogen has the potential to ignite and explode given the right conditions—this is a chemical property. Metals in general have the chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas—this is a chemical property.
The more general term for rusting and other similar processes is corrosion. Other terms that are commonly used in descriptions of chemical changes are burn, rot, explode, decompose, and ferment. Chemical properties are very useful in identifying substances. However, unlike physical properties, chemical properties can only be observed as the substance is in the process of being changed into a different substance.
Physical properties include color, density, hardness, and melting and boiling points. A chemical property describes the ability of a substance to undergo a specific chemical change. 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. This page was constructed from content via the following contributor s and edited topically or extensively by the LibreTexts development team to meet platform style, presentation, and quality:.
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. Within the overall diamond symbol, the top red diamond specifies the level of fire hazard temperature range for flash point. The blue left diamond indicates the level of health hazard. The yellow right diamond describes reactivity hazards, such as how readily the substance will undergo detonation or a violent chemical change.
Each hazard is rated on a scale from 0 to 4, with 0 being no hazard and 4 being extremely hazardous.
While many elements differ dramatically in their chemical and physical properties, some elements have similar properties.
We can identify sets of elements that exhibit common behaviors. For example, many elements conduct heat and electricity well, whereas others are poor conductors. These properties can be used to sort the elements into three classes: metals elements that conduct well , nonmetals elements that conduct poorly , and metalloids elements that have properties of both metals and nonmetals.
In order for you to do this you will be given a list of substances from which your substance was chosen. You will need to look up some of the properties of these substances in the literature.
You can then compare the properties that you observed in lab with those that you found in the literature to identify your unknown substances. Be careful not to burn yourself with either the Bunsen burner or the melting point apparatus. Do not breathe the vapors of the solids as you attempt to burn them; burn them near or under a snorkel. Obtain 2 unknowns from your instructor and record the code numbers of your unknowns in your record book.
Solubility in Water. For each unknown determine the solubility in water as follows:. Place 0. Add 1 mL of water from a 10 mL graduated cylinder and stir the mixture with a stirring rod. If after 2 minutes the solid has not all dissolved, add another milliliter of water and repeat the stirring process. Continue adding water in 1 mL increments until all the solid has dissolved and then record the total volume of water required to dissolve each solid. If the solid does not dissolve after the addition of mL of water, discontinue the addition of water and record the fact that the solid did not dissolve after the addition of 20 mL of water in your record book.
Based on this data alone, classify your unknowns as either ionic or molecular. Add 1 g of each solid in a 50 mL beaker along with about 20 mL of water.
Stir the mixture thoroughly for 1 to 2 minutes and test the conductivity of the solution even though the sample may not completely dissolve. Your instructor will show you how to measure the conductivity. Record whether the solution resulted in the light shining brightly, dimly, or not at all.
A bright light indicates that the solid is an electrolyte; no light at all indicates that the substance is a nonelectrolyte. Physical properties include: appearance, texture, color, odor, melting point, boiling point, density , solubility, polarity, and many others. The three states of matter are: solid, liquid, and gas. The melting point and boiling point are related to changes of the state of matter.
All matter may exist in any of three physical states of matter. In the graphic on the left the solid and liquid forms of water - ice are shown. Physical Changes:. A physical change takes place without any changes in molecular composition. The same element or compound is present before and after the change.
0コメント