Properties of Matter: A Closer Look

Properties of M atter & I dentifying Substances 1 Compound – when two or more elements combine chemically. Mixture – when two or more substances are combined but do not join together. Chemical Formula – uses chemical symbols and subscripts to identify the number of atoms of each element in a molecule of a compound. Period – the horizontal rows on the periodic table. Periods are numbered 1 to 7. The elements in periods are arranged in order of increasing atomic number. Group or “Family” – the vertical columns on the periodic table. Groups or Families are numbered 1 to 18 (as well as from 1A to 8A). Elements in the same group or family have similar chemical properties. The elements in a group all share the same number of valance electrons. NOTE : Elements in groups 1-2 and 13-18 are the main group elements. Elements in groups 3-12 are called transition elements. Reactivity – describes how likely an element is to form bonds with other elements. Physical Property – a characteristic of a substance that can be observed without changing the identity of the substance. Chemical Property – a characteristic that describes how the matter will change under certain conditions causing the substance to change it’s identity. Metal – an element that is a good conductor of electricity and heat. Nonmetal – an element that DOES NOT readily conduct electricity or heat. Metalloid – an element that has properties of both metals and nonmetals. Inert – elements that are unable to react chemically. Malleable – able to be hammered and shaped or rolled into thin sheets. Ductile – able to be stretched or drawn into wires without breaking. 2 Magnetism – a force of attraction or repulsion that exists. Conductor – a material or substance that allows electrons to flow through it easily. Insulator – materials or substances that DO NOT allow electricity to flow through them easily. Semiconductor – materials or substances that has properties of both conductors and insulators. Density – D=M/V, the ratio of mass to volume. Solubility – a measure of how much of a substance dissolves in a given amount of another substance. (Ex : The m easurem ent of how m uch salt dissolved in 1 cup of w ater) Soluble – able to dissolve. (Ex: W ater is soluble, it is able to dissolve) Solute – the substance dissolved in a given solution. (Ex: Kool-Aid pow der is a solute) Solvent – a substance in which another substance dissolves. (Ex: W ater dissolves other substances. W ater is the “Universal Solvent.”) Solution – a mixture in which the particles are too small to be distinguished from each other and remain constantly and uniformly mixed. (Ex : Kool-Aid pow der, w ater and sugar w hen prepared together rem ain constantly and uniform ly m ix ed.) Melting Point – the temperature at which a solid changes to a liquid. Boiling Point – the temperature at which gas bubbles form in a liquid and rise to the surface to escape the liquid as a gas. Specific Heat – the amount of heat needed to raise 1 gram (1g) of a substance by 1 degree Celsius (1oC). The unit of measurement is J/goC.