Elements, Compounds and Mixtures

1. Elements, Compounds and Mixtures

2. 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.

3. 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.

4. 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.

5. 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.

6. 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

7. 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

8. 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.

9. 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.