[CHEM] Matter

• Matter can be identified by its PHYSICAL and CHEMICAL properties.
• Physical Properties are the characteristics that we observe without changing the substance, such as color, odor, melting point, boiling point, density, solubility, etc.
• Chemical Properties are characteristics that can be observed when a substance changes its composition, such as reactivity, flammability, acidity/basicity, toxicity, etc.
• The ability of water to undergo electrolysis is among its chemical properties. In electrolysis, an electric current is passed through liquid water to decompose the substance intro hydrogen and oxygen gases.
• Changing ice into water is among its physical properties.
• Dissolving a tablespoon of brown sugar in a glass of water is among its physical properties.
• • The physical properties of matter include the following:
  • melting point
  • boiling point
  • odor
  • color
  • taste
  • solubility
  • density
  • hardness
  • softness
  • volatility
  • ductility
  • malleability
  • viscosity
  • heat conductivity
  • electrical conductivity
• Reactivity is a chemical property observed when a substance reacts with another substance. At the same time, it is still considered a chemical property if a substance does not react with another substance because it is inert or more stable than the other substance.
• Matter may be classified as pure substances or mixtures.
• Pure substances are forms of matter that have a definite chemical composition.
• Pure substances can be classified as elements or compounds.
• Elements are substances that are made up of only one type of atom. They cannot be broken down into simpler substances by ordinary chemical means.
• Elements exist as diatomic or polyatomic molecules.
• Diatomic molecules are composed of two chemically bonded atoms of the same element, while polyatomic molecules are composed of three or more atoms of the same element.
• Radioactivity is the spontaneous emission of energetic particles from an atom, such as cobalt-60 (used in gamma radiation to treat cancer) and cesium-137.
• Compounds are substances made up of more than one type of atom.
• Water is an example of a compound comprising hydrogen and oxygen atoms.
• Carbon dioxide is an example of a compound comprising carbon and oxygen atoms.
• Table salt is an example of a compound comprising sodium and chlorine atoms.
• Atoms in compounds are chemically combined in definite proportions. They can be decomposed into two or more simpler substances by ordinary chemical reactions.
• The properties of a compound are often very different from those of the elements that compose it. Example is the properties of sodium chloride (NaCl), comprising of sodium (Na) and chlorine (Cl2) elements.
• Mixtures are made of two or more substances that are physically combined.
• Mixtures are classified as homogenous or heterogenous.
• Homogenous mixtures have only one phase or uniform appearance throughout. Any portion of the sample has the same properties and composition.
• Solutions, such as salt water and rubbing alcohol, are considered homogenous because they have only one phase.
• A solution is a homogenous mixture of two or more substances in a variable composition. This means that different mixtures of the same element may have different proportions.
• The parts of a solution are physically, not chemically, combined. Mixing salt and water will not make the salt chemically react with the water. The two parts just mix so well that the resultant solution has uniform properties all throughout.
• Examples of solutions include tea, coffee, metal alloys, and the air you breathe.
• Solutions are made up of two parts: a) the solute that gets dissolved and b) the solvent that does the dissolving. In the case of salt water, salt is the solute and water is the solvent.
• Heterogenous mixtures form more than one phase and the components are visibly distinguishable from one another.
• Examples of heterogenous mixtures are soil and salad dressing.
• The components of mixtures, both homogenous and heterogenous, can be separated by physical means.
• Physical separation methods include filtration, evaporation, sublimation, distillation, decantation, crystallization, and use of sieves and magnets.