Classifying and Describing Matter

Classifying and Describing Matter

Classifying Matter

SubstancesThe units that make up all matter are called atoms.If all the atoms in a sample of matter have the same identity, that kind of matter is called an element.Matter that has the same composition and properties throughout is called a substance.

In order to be classified as an element, you must be found on the periodic table!

CompoundsA compound is a substance made up of more than one element bonded together.Compounds often have properties that are different from the elements that make them up.Elements and compounds cannot be reduced to more basic components by physical processes.Chemical FormulasChemical formulas tell you which elements make up a compound as well as how many atoms of each element are present.

The formula of a compound communicates its identity and makeup to any scientist in the world.

What am I?

What am I?I am sodium.My symbol is Na.I am an element!

What am I?

What am I?I am hydrochloric acidMy formula is HCl (that is an L not an I)I am a compound

What am I?

What am I?I am calcium carbonateMy formula is CaCO3I am a compound

What am I?

What am I?I am cubic zirconiaMy formula is ZrO2I am a compound

MixturesWhen two or more substances (elements or compounds) come together but dont combine to make a new substance, a mixture results. The proportions of the substances in a mixture can be changed without changing the identity of the mixture.Mixtures can be classified as homogeneous or heterogeneous.Homogeneous MixturesHomogeneous mixtures (or solutions) are evenly mixed and considered to be the same throughout.

Heterogeneous MixturesHeterogeneous mixtures are not well mixed and the different parts can be easily seen.

ColloidsA colloid is a type of mixture that never settles.Its particles are larger than those in solutions but not heavy enough to settleA light beam is invisible as it passes through a solution, but is scattered as it passes through a colloidThis scattering of light by colloidal particles is called the Tyndall effect

Tyndall Effect

SuspensionsA suspension is a heterogeneous mixture containing a liquid in which visible particles settle

Suspension

Notice the two distinct layersWhat am I?

What am I?I am salt waterI am a mixture of salts and waterI am a homogeneous mixture

What am I?

What am I?I am oil and vinegarI am a mixtureI am a suspension

What am I?

What am I?I am milkI am a mixtureI am a colloid

SolutionsTo describe a solution, you may say that one substance is dissolved in anotherThe substance being dissolved is the solute and the substance that dissolves the solute is the solventGenerally, the substance present in the largest amount is considered to be the solvent

DissolvingStirring a solution speeds up dissolving because it brings more fresh solvent in contact with more soluteParticle size is another factor in the speed of dissolving (the smaller the faster)Increasing temperature will increase the rate at which most solids dissolveStirring or shaking a solution of gas in a liquid causes the gas to come out of a solution fasterGases are more soluble in colder temperaturesRate of Dissolving

Solubility and ConcentrationSolubility of a substance is the maximum number of grams of the substance that will dissolve in 100 grams of solvent at a certain temperatureA concentrated solution is a solution where there is more solute than solvent presentA dilute solution is a solution where there is more solvent than solute presentSaturationA saturated solution is a solution that has dissolved all the solute it normally can hold at a given temperatureAn unsaturated solution is any solution that can dissolve more solute at a given temperatureA supersaturated solution contains more solute than a saturated one has at that temperature

Describing Matter

Physical PropertiesAny characteristic of matter that you can observe without changing the substances that make up the material is known as a physical property.Examples of physical properties include size, shape, color, density, melting and boiling points, texture, magnetism, volume, temperature, and odorPhysical ChangesA change in size, shape, or state of matter is called a physical change.Physical changes do not change the identities of the substances in a material

Chemical PropertiesA chemical property is a characteristic of a substance that indicates whether it can undergo a certain chemical change.Examples of chemical properties include oxidation, combustibility, and flammability.Chemical ChangesA change of one substance in a material to a different substance is a chemical change

What kind of Change?

What kind of change?Candle wick is burningChemical ChangeCandle is meltingPhysical Change

What kind of change?

What kind of change?Bread is bakedChemical Change

Nuclear Reactions

Nuclear FissionThe process of splitting a nucleus into two nuclei with smaller masses is called nuclear fissionThe total mass of the products is slightly less than the mass of the original nucleus and the neutronThis small amount of missing mass is converted to a tremendous amount of energy during the fission reactionFission Reaction

Fission

Nuclear FusionFusion fuses atomic nuclei together, while fission splits nuclei apart.With nuclear fusion, lower-mass nuclei fuse together to form a single more massive nucleus + energy. The sum of the masses of the two low-mass nuclei equals the mass of the single, massive nucleus plus the energy released (divided by c2).Low mass nucleus + low mass nucleus = single massive nucleus + (energy released / c2)Remember E = m c2 The ``c'' is the symbol for the speed of light. Nuclear fusion can power the Sun for about 10 billion years. Fusion ReactionDeutrium and Tritium are two isotopes of hydrogen that differ in the number of neutrons in the nucleus.Notice that the products of nuclear fusion have less mass! The missing mass was converted to an incredible amount of energy!

A closer look at Nuclear Fusion

Nuclear fusion is actually a little more complicated than shown in the previous slideLaw of Conservation of MassThe statement: Matter is neither created nor destroyed during a chemical change is known as the Law of Conservation of MassAccording to this law, the mass of all substances present before a chemical change equals the mass of all substances after the change.Remember that a nuclear reaction is NOT a chemical reaction!