Presentation on theme: "E lements Chapter 4 Section 1. What are elements? An element is a pure substance that can not be separated into simpler substances by physical or chemical."— Presentation transcript:
What are elements? An element is a pure substance that can not be separated into simpler substances by physical or chemical means.
What is a pure substance? A pure substance is a substance in which there is only one type of particle. All particles of a pure substance are identical.
Every element has unique set of properties which are used to identify that element. A. Characteristic properties b. Physical pproperties c. Chemical properties
4. Using examples given on page 83 please complete the following: Cob alt : Me lting point: _____________ Density:_________________ Physical properties: _____________________________________________ Chemical properties: ____________________________________________ Iron: Melting point: ____________________ Density:___________________________ Physical properties:________________________________________________ Chemical properties:_________________________________________________
Why are most elements on earth not found in their pure form? Because most elements in nature react with oxygen and water to form compounds.
Copper Sheet Iron Ore as found in nature Iron as used for construction Gold bars Lead casing used to store radioactive elements.
How are elements classified? a. Metals b. Non metals c. Metalloids
What are metals? They are shiny. They can conduct electricity. Can conduct thermal energy. Malleable which means they can be pounded into sheets. Ductile which means they can be drawn into wires. Examples:
What are metalloids? They are semiconductors. can have both metal and non-metal properties. some are shiny and some are dull. can be somewhat mmalleable some can conduct heat and electricity. Examples: silicon, boron, antimony
8. What are non metals? No n metals: dull not shiny Poor conductors of heat and electricity when in solid form they are brittle and not malleable few can be used to make various products in their pure form Neon a gas can be used to create lights Graphite a very soft element is used when making pencils.
Graphite as found in nature Graphite centers in pencils
Silicon is used in making of computer chips and computer circuits. Boron is used in making old fashioned detergents such as Borax and insect and roach killers. Antimony is used in making materials which can then be used in making of industerial plastic containers.
What are compounds? A compound is a pure substance composed of two or more elements that are chemically combined. Elements must undergo chemical change before a compound can be formed.
Compound can be simple such as water H2o. Compounds can be large and complex such as proteins.
When compound form elements join in specific ratios according to their atomic masses. Water is made of two hydrogens and one oxygen at the ratio of 1:8 Hydrogen peroxide is made of two hydrogens and two oxygens at the ratio of 1:16.
Carbon dioxide is made of one carbon and two oxygen with a ratio of 3:8. Carbon Monoxide is made of one carbon and one oxygen at the ratio of 3:4.
Every compound has a unique set of properties such ad chemical and physical properties. These properties are different than the properties of the elements that make them.
Solutions Made up of two or more ssubstances appear to be one substance because the particles of one substance are distributed evenly in the other substance
Solutions can be made from Two lliquids one liquid and one solid Liquids and gases d ifferent gases different solids
Solutions are made up of a solute and a solvent. Solute dissolves in a solvent.
Homogeneous solutions H ave the same appearance and properties through out The solute completely dissolves in a solvent in this type of solution.
Heterogenous solutions are made up of insoluble salutes which do not dissolve in a solvent. T his type of mixture is known as a suspension.
Particles of a solute in a homogeneous solution are extremely small vs. the larger particles of a suspension. This means that light can pass through a solution, but is scattered by the particles of a suspension.
Concentration A measure of the amount of solute dissolved in a solvent. stated in grams of solute per mL of ssolvent important for medications
Solutions can be: Concentrated dilute Saturated unsaturated
Concentrated : has more solute than solvent dilute: has more solvent that ssolute saturated: contains all the solute it can hold at a given temperature. unsaturated: does not contain all the solute it can hold at a given temperature.
Solubility refers to the amount of solute needed to make a saturated solution using a given amount of solvent at a certain temperature. It is expressed in grams of solute per 100 mL of solvent.
Solubility is effected by : Mixing heating crushing
Mixing: Includes stirring as well as shaking. increases the rate of solubility of a solute in a solvent. it helps speed the process of solubility because it causes the particles to spread out and come into contact with the particles of a solvent.
Suspensions Particles of the solute in this type of solution are so heavy that the settle out. These particles are insoluble. these are known as heterogeneous suspensions. The particles can scatter light and can be separated by filter action.
Colloids Have the properties of both solutions and suspensions. their particles are insoluble like a suspension, but are not heavy enough to settle out like a suspension so they spread out like the particles of the solution. can be solids, liquids or gas. The particles scatter light like a suspension.