Elements, Compounds And MixturesPresentation Transcript
Elements, Compounds and Mixtures
What is an element? Element- is a pure substance that cannot be separated into a simpler substance by physical or chemical means. Elements only have one type of particle. A pure substance is a substance in which there is only one type of particle. Ex- atom * In a 5g nugget of the element gold, every particle is just like the rest of the particles in that 5g nugget.
Elements Continued The particles of a pure substance are alike no matter where that substance is found. Ex- the atoms of iron (element) are all alike whether they are in a meteorite or in an iron skillet. Every element has a unique set of properties In order to identify an element, you can look at its properties. These properties do not depend on the size of the example.
Properties of an element There are several ways to identify an element. You must look at their individual properties. *elements are grouped according to their shared properties. Ex. Iron, nickel and cobalt. All three of these elements are shiny, all three conduct thermal energy and electric current. Since these three things have this stuff in common, they are grouped together in a grouped called Metals.
Three categories of elements Metals- these elements are shiny, are good conductors of thermal energy and electric current. They are malleable and ductile. Ex- Lead, copper and tin Nonmetals-are elements that are dull and that are poor conductors of thermal energy and electric current. Solid nonmetals tend to be brittle and unmalleable. Ex- the neon used in lights and graphite used in pencils.
Categories of elements con’t Metalloids- also referred to as semiconductors. These are elements that have properties of both metals and nonmetals. Some metalloids are shiny while others are dull. Some conduct thermal energy and currents while others do not. Some are malleable and some are not. Ex- silicon, Boron and Antimony
Compounds A compound is a pure substance composed of two or more elements that are chemically combined. In a compound, a particle is formed when atoms of two or more elements join together. In order for these elements to combine, they must react, or undergo a chemical change together. Ex- table salt..NaCl, water…H2O, sugar…CHO, carbon dioxide…co2, baking soda, NaHCO
Compounds con’t The compound is a new pure substance that is different from the elements that reacted to form it. Compounds are not random combinations of elements. When a compound forms, the elements join in a specific ratio according to their masses.
Compounds Properties Each compound has its own unique set of properties. These properties allow you to distinguish it from other compounds. Ex- Melting point, boiling point, density, color, chemical properties. A compound has different properties from the elements that formed it. Ex- Table Salt- made from two dangerous elements. When mixed together, they form a harmless compound.
Compounds Cont. Sodium- is a soft silvery white metal that reacts violently with water Chlorine-is a poisonous, greenish yellow gas. Put the two together= sodium chloride!! Table Salt, a perfectly safe, edible compound
Compounds can be broken down Some compounds can be broken down into elements through chemical changes. Other compounds undergo chemical changes to form simpler compounds. Ex- when mercury II oxide (compound) is heated, it breaks down into the elements mercury and oxygen. Also, if an electric current is passed through melted table salt, the elements sodium and chloride are produced.
Compounds CANNOT be…… Broken down by physical changes. If you pour water through a filter, there will be no change. Compounds can only be broken down through a chemical change. Compounds in Nature- Proteins, nitrogen compounds, carbon dioxide. Compounds in Industry- Ammonia, aluminum.
Mixtures A mixture is a combination of two or more substances that are not chemically combined. Substances in a mixture retain their identity- because there is no chemical changes that occurs in mixtures, each of the substances keeps its original identity. Ex- cheese and tomato sauce. They do not react to each other, yet they mix. Thus, resulting in a mixture.
Mixtures can be physically separated If you don’t want pepperoni on your pizza, you can easily pick them off, right? This is a physical change of the mixture. The pizza and the pepperoni keep their original identity whether or not the pepperoni is on it or not. HOWEVER, not all mixtures are as easily separated as pizza and pepperoni. Ex-saltwater. You can’t easily pick the salt out of the water. How would you remove salt from water?
Ways to separate mixtures Distillation- the process that separates a mixture based on boiling points of the compounds. Ex-distilling saltwater Magnet- can be used to separate a mixture of the elements iron and aluminum. Iron is attracted to the magnet, but the aluminum is not.
Solutions A solution is a mixture that appears to be a single substance, but is composed of particles of two or more substances. The process in which particles of substances separate and spread evenly is known as dissolving. Ex- Kool Aid and water. Solute- the substance that is dissolved-Kool Aid Solvent- the substance in which the solute is dissolved- water