Chemical Properties - SchoolRack：化学性质-.pptx

What is a Physical Property? ? Any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. ? Viscosity, conductivity, malleability, harness, melting and boiling points, density, and temperature are just a few examples. Viscosity ? The tendency of a liquid to keep from flowing- its resistance to flowing. ? The higher the viscosity of a liquid, the slower the liquid moves. ? When a substance is heated, the viscosity of that substance lowers. Conductivity ? A material ’ s ability to allow heat to flow. ? Materials with a high conductivity are called conductors. Malleability ? The ability of a solid (metal) to be shaped without breaking. Hardness, Melting & Boiling Points ? To test hardness of material, you see which material can scratch the other. ? Melting Point: The temperature at which a substance changes from a solid to liquid. ? Boiling Point: The temperature at which a substance boils. Density ? Density is a ratio of the mass of a substance to its volume d=m/v ? Objects made out of the same material have the same density. ? Density can be used to test the purity of a substance. Using Properties to Separate Mixtures ? Filtration: A process that separates materials based on the size of their particles by using a strainer or filter. ? Distillation: A process that separates the substance in a solution based on their boiling points. Physical Changes ? Occurs When some of the properties of a material change, but the substances in the material remain the same. ? Some physical changes can be reversed. ? Freezing, melting, then freezing water again What is a Chemical Property? ? Any ability to produce a change in position of matter. ? Can only be observed when the substances in a sample of matter are changing into different substances. Examples ? Flammability ? The material ’ s ability to burn in the presence of oxygen. ? Lighting a candle ? Reactivity ? How