A model is a simplified approximation of reality. ◦ Architects build models before the actual construction ◦ Business owners build models Science models are simplified but, useful as a representation of what the structure will be like ◦ Models are not always physical entities ◦ Some could simply be a set of ideas
All matter is composed of tiny Particles These Particles are in constant motion The amount of motion is related to temperature. Increased temperature represents increased motion Solids, gases, and liquids differ in the freedom of motion of their particles and in how strongly the particles attract each other.
Particles of a solid can be pictured as tiny spheres held closely together When a solid is heated, the average speed of the moving particles increases. Faster-moving particles collide more violently, causing each particle to push its neighboring particle far away Therefor the increase in temperature usually causes the solid to expand
Particles in a liquid are still close together but, have more empty space between them than in a Solid Liquids normally expand to fill a slightly larger volume Attractions between them keep then a certain distance apart Freedom of movement allows liquids to take the shape of their container
Particles of a gas are much father apart than a solid or liquid According to the model each particle in a gas moves freely in a straight-line path until it collides with another particle Particles are moving very fast and normally bounce off each other and continue on their own path
Scientific Investigation ◦ Are all the particles in a solid, liquid, or gas identical? ◦ What are the particles made of? Materials ◦ Glass of Water ◦ Dissolved table salt
1. Heating can separate the salt and water (Distillation) ◦ The water will evaporate thus, leaving the salt ◦ Using the distillation apparatus water vapor will be cooled and placed into a separate container2. Run electric current through water and break down into Hydrogen gas and Oxygen Gas3. Run electric current through melted dry salt and break down into Sodium metal and Chlorine gas
Salt water has been broken down into 4 elements or building blocks of matter ◦ Elements –are substances that cannot be chemically converted into simpler ones
Water consist of ◦ Hydrogen ◦ Oxygen Salt consist of ◦ Sodium ◦ Chlorine These are both chemical compounds (covered in Chapter 3) The mixture of the two are known as a solution (covered in Chapter 4)
There are current 114 elements ◦ 24 are not naturally found on Earth 2-3 might exist in Stars ◦ Some elements found in nature are Unstable These elements exist for a limited time and then turn into other elements via radioactive decay ◦ Of the 83 stable elements found in nature, many are rare and will not be mentioned in this text
Each element is known by name and a symbol They are named in a variety of ways ◦ The elements Francium and Californium were named to honor the places where they were discovered. ◦ Some reflect the source from which the element was first isolated Hydrogen came from the Greek words water(hydro)- forming(genes) ◦ Some elements are named for their appearance Idos means violet in Greek
Symbols are also chosen in a variety of ways ◦ Some are the first letter of an elements name C represents Carbon When two letters are used the first is capitalized the second is lowercase Cl is chlorine and Co is cobalt ◦ Some symbols use the Latin names for the elements Na is sodium (Latin natrium) Au is gold (Latin aurum) means shining dawn Most recent are not named yet are given temporary names and three letter symbols
Arranged in groups or families that have similar characteristics ◦ They are in columns ◦ They are commonly referred to as Groups or Families ◦ Groups are numbered 1-18 ◦ Groups A or B This convention is explained and illustrated better on the following slide
Properties ◦ Metals have a shiny metallic luster. ◦ Metals conduct heat well and in the solid form conduct electric currents. ◦ Metals are malleable, which means they are capable of being extended or shaped by the blows of a hammer.
Characteristics ◦ Some are gases at room temperature and pressure ◦ Some are solids ◦ Only one is a liquid ◦ They do not have the characteristics listed previously for metals
Characteristics ◦ Have some but not all the characteristics of metals Metalloids include: ◦ Boron ◦ Silicon ◦ Arsenic ◦ Tellurium ◦ Astatine ◦ Germanium ◦ Antimony ◦ Polonium
When an element has two or more atoms, each with the same number of protons but a different number of neutrons, the different species of element are called isotopes.
Atomic number is the number of protons in an uncharged atom Atomic mass is the sum of protons and neutrons in an atom*The Atomic number of an isotope is the samebut, not the mass number because of thedifference between the number of neutrons. Tospecify the different isotopes the mass numberwith follow the symbol for the element.