Elements, Compounds, and Mixtures

What Do You Think?

How is an element different from a

compound?

Answer

An element is made up of only one pure substance, and a compound is composed of two or more elements that are chemically combined.

Gold

Water

http://www.nbmg.unr.edu/slides/water/5.htm

http://www.worldofrockhounds.com/huge-gold-nugget-sm.JPG

Elements

An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.

Elements

Every element has a unique set of properties.

The Periodic Table of Elements is arranged according to these properties.

Elements

Every element has a unique set of properties.

Some physical properties that are used to classify elements are boiling point, melting point, color, and density.

Elements

Chemical properties used to separate elements from each other include reactivity with acids, or reactivity with oxygen.

Elements Are Grouped

Some elements are shiny, and can conduct thermal energy. They are all grouped together on the left hand side of the Periodic Table. They are called metals. Not all metals are exactly alike, but they do have some properties in common.

Elements

Elements Can Be Identified By Categories

If you know the category, you know the properties.

Try this!

1. Share with your class how CDs can be classified by

categories?

2. How can dogs be classified by categories?

Elements

Elements are

identified by 3 main categories

• Metals

• Nonmetals

• Metalloids

Elements

Metals are elements that are usually shiny and good conductors of electricity and heat.

Metals

Elements

Metals are also malleable (can be hammered into thin sheets).

Metals

Elements

• Metals are ductile, or can be drawn into thin wires

• Metals are located to the left of the “zig zag line” on the Periodic Table

Elements

• Examples: Iron (Fe) and Copper (Cu).

http://www.flamo.net/crystals/iron.jpg http://resourcescommittee.house.gov/subcommittees/emr/usgsweb/materials/copper.html

Elements

Nonmetals

• Usually dull and poor conductors of heat and electric current

• Tend to be brittle and unmalleable

• Mostly gases

Elements

Nonmetals

• Examples: Neon (Ne) and Carbon (C)

www.neonstreet.com/ sign2.html reluctant-messenger.com/ diamond_sutra.htm

Elements

Metalloids

• Share properties of both metals and nonmetals

• Can be shiny or dull

• Somewhat malleable and ductile

• Semiconductor

Elements

• Metalloids touch the “zig zag line” on the Periodic Table

• Examples:

Silicon (Si) Arsenic (As).

Let’s Review!

- 1 -

Describe some physical properties of the element iron.

http://neil.fraser.name/news/2004/05/22/

Answer

Physical properties include:

1. Melting Point: 1535 °C

2. Density: 7.9 g/cm3

3. Iron has the ability to conduct heat and electrical current

Let’s Review

- 2 -

What is an example of a metal that is very

malleable, shiny, and is used often in kitchens?

Answer

Aluminum Foil

Compounds

What do salt, sugar, baking soda, and

water have in common?

What Do You Think?

CompoundsA compound is a pure substance composed of two or more elements that are chemically combined.

Familiar Compound

Compound Elements Combined

Table Salt Sodium and Chlorine

Water Hydrogen and Oxygen

Sugar Carbon, Hydrogen, and Oxygen

Carbon Dioxide Carbon and Oxygen

Baking Soda Sodium, Hydrogen, Carbon, and Oxygen

Compounds

Properties of Compounds

• Compounds, like elements, can be identified by their own physical and chemical properties

• What are some examples of physical and chemical properties?

Compounds

Each compound has different properties than the elements that make them up.

Water Hydrogen Oxygen

Melting Point 0°C -259.14 °C -218.4 °C

Boiling Point 100 °C -252.87 °C -183.0 °C

Density 1.0 g/cm3 0.08988 g/cm3 1.429 g/cm3

State at Room Temperature Liquid Gas Gas

Compounds

Compounds are Composed of Elements.

The compound Water is composed of Hydrogen and Oxygen chemically bonded together.

Compounds

Compounds are Composedof Elements.

• The compound Ammonium is composed of Nitrogen and Hydrogen chemically bonded together

Let’s Review!

- 1 -

What is the difference between an element and a

compound?

Answer

• An element is a pure substance that cannot be separated into simpler means by physical or chemical means

• A compound is a pure substance composed of two or more elements that can be broken into simpler substances by a chemical change