Part 6: Read the Passage below and complete the chart. Chemical & Physical Properties Each substance has its own unique combination of physical and chemical properties, and substances can be identified based on these properties. Physical Properties Physical properties are characteristics of an element or compound that can be observed without changing the identity of the substance. They are the properties that the substance already has. Color, density, mass, and solubility are all physical properties. Some physical properties change depending on the amount of the substance present. These properties are called extrinsic properties. Mass and volume are examples of extrinsic properties. Other physical properties are not dependent on how much of the substance is present. These are called intrinsic properties. Boiling point and density are two examples of intrinsic properties. Whether you have a cup of water or an entire pot filled with water, the water in both will boil at 100 °C (at sea level). The water in both containers will also have the same density of about 1.0 g/mL (at 25 °C). Intrinsic properties are useful when identifying an unknown substance. During a physical change, substances are not altered chemically. They simply change from one state of matter to another, or they separate or combine without breaking or making bonds. Changes of state are physical changes. Making and separating mixtures are also physical changes. Mixtures can be separated using the differences in physical properties of each substance. Important physical properties. ● Mass is the amount of matter in an object. Mass is different from weight. ● Weight is a force due to the pull of gravity on an object. The mass of an object stays constant in all situations. Weight, however, is influenced by the strength of the gravitational pull. Therefore, weight changes depending on the forces of gravity at that location. For example, the same object will weigh more on the Earth than it does on the Moon because the gravitational pull of the Earth is greater than the gravitational pull of the Moon. It's mass, though, will be the same on Earth as it is on the Moon because the amount of matter does not change. ● Volume is the amount of space occupied by a substance; size. ● Density is how much mass a material has per unit of volume. Denser materials have more matter in a given space than less dense materials. Density is found by dividing the mass of an object by its volume. ● The boiling point is the temperature at which a liquid changes to a gas. For water, it is 100 °C or 212 °F. ● The melting point is the temperature at which a solid changes to a liquid. The melting point of water is 0 °C or 32 °F. ● The freezing point is the temperature at which a liquid changes to a solid. The melting and freezing points for most substances are the same temperature, and the direction of heat flow determines whether the substance is melting or freezing. The freezing point of water is 0 °C or 32 °F. ● Solubility refers to the ability of a substance to dissolve in a solvent such as water or the amount of a substance that can dissolve in a certain amount of water. The solubility of salt is about 36 grams per 100 mL of water. ● Viscosity refers to how easily a liquid is able to flow. ● Conductivity refers to the ability of a substance to transmit energy. Usually this refers to its ability to conduct electricity, but it may also refer to its ability to conduct heat. Metals and solutions that contain ions, such as HCl in water, can usually conduct electricity. ● Compressibility refers to the ability of a given mass of a substance to decrease in volume in response to the application of an outside force. ● Magnetism refers to the ability of a substance to respond to a magnetic field. Metals such as iron, nickel, and cobalt are magnetic because they can be attracted by magnetic fields. In general, compounds that have larger particles and/or strong forces between the particles are likely to have higher melting and boiling points because more energy is required to separate the individual particles from one other. This also means that they are likely to be solids or liquids at room temperature. Chemical Properties Chemical properties are the characteristic ways in which an element or compound chemically behaves. They describe how substances react under certain conditions and with other substances. Chemical properties primarily depend on the types of atoms and bonds that are in a substance. During a chemical change, a chemical reaction takes place. Atoms are rearranged by making and/or breaking bonds to form new substances with different properties. Chemical properties and changes can be used to identify a substance, but these methods always change the substance into a new compound. Important chemical properties ● Reactivity describes whether a substance reacts easily with other substances. For example, most metals will react with acids. ● An unreactive substance does not react easily with most other substances. The noble gases are the least reactive elements, and water is an example of an unreactive compound. ● The ability to react with acids or bases describes whether or not a substance reacts chemically with an acid or a base. ● Flammability describes the ability of a substance to ignite or burn. ● Combustibility describes the ability of a substance to react rapidly with oxygen and release energy in the form of heat and/or light. ● The ability to oxidize or the ability to rust refers to the tendency of some metals to rust or corrode by reacting with oxygen in the air. ● The ability to tarnish refers to the tendency of some metals to react easily with certain gases in the air. This causes discoloration at the surface of the metal. Complete the chart below by writing 4 facts about each of the topics. Use the information from the passage you just read. You must write in complete sentences.
Physical Properties Examples of Physical Properties Chemical Properties Examples of Chemical Properties