MATTER

Chapter 18

Concept Mapmatter atoms

protons positive

neutrons negative

electrons neutral

is made up of

charge charge

All About Atoms

The Periodic Table

 Elements as Building Blocks

The periodic table is organized like a big grid. The elements are placed in specific places because of the way they look and act. If you have ever looked at a grid, you know that there are rows (left to right) and columns (up and down). The periodic table has rows and columns, too, and they each mean something different.

Compoundspages 523 - 526

• When atoms of more than one element combine, they form a compound.

• A compound contains atoms of more than one type of element that are chemically bonded together.

http://www.webelements.com/webelements/scholar/elements/argon/compounds.html

Compoundspages 523 - 526

• Water is a compound consisting of molecules made up of one oxygen atom bonded to two hydrogen atoms

http://visionlearning.com/library/x_linker.php?moid=2120

http://en.citizendium.org/wiki/Water

• If water is a molecule, is it also a compound because the hydrogen and oxygen have been chemically combined? If so, how do you determine whether a substance is a compound or a molecule?

• A molecule is what you get when any atoms join together.• A compound is what you get when atoms of two or more different

elements join together.

• All compounds are molecules, but not all molecules are compounds.

• Water (H2O) is a molecule because it is made from atoms that have been chemically combined. It is also a compound because the atoms that make water are not all the same - some are oxygen and some are hydrogen.

• Oxygen in the atmosphere is a molecule because it is made from two atoms of oxygen (O2). It is not a compound because it is made from atoms of only one element - oxygen. This type of molecule is called a diatomic molecule, a molecule made from two atoms of the same type.

Author: Steve Gagnon, Science Education Specialist

Compoundspages 523 - 526

• Let's look at an example.  The element sodium is a silver-colored metal that reacts so violently with water that flames are produced when sodium gets wet.  The element chlorine is a greenish-colored gas that is so poisonous that it was used as a weapon in World War I.  When chemically bonded together, these two dangerous substances form the compound sodium chloride, a compound so safe that we eat it every day - common table salt!

sodium metal - Na chlorine gas - Cl table salt - NaCl

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Compounds Quiz

Chemical Formulas Quiz

Bondingpages 524 - 526

The forces that hold the atoms in compounds together are called chemical bonds.

Atoms that have eight electrons in the outermost portion of their electron cloud are not likely to combine with other atoms. If an atom has fewer than eight electrons in the outermost shell, it is unstable and is more likely to combine with other atoms

Bondingpages 524 - 525

When two atoms share a pair of electrons this forms a covalent bond.

For example, two atoms of hydrogen can share outer electrons with one atom of oxygen to form a molecule of water.

http://www.evans2chemweb.co.uk/chemwebdata/images/water2d.gif

Bondingpages 524 - 525

When an electron leaves one atom and enters another, the two atoms become ions held together by an ionic bond.

Table Salt forms when a sodium ion and a chlorine ion are attracted to one another.

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Metallic bonds are found in metals such as copper, gold, aluminum, and silver. In this type of bond, electrons are free to move from one positively charged ion to another.

The movement of electrons, or conductivity, allows metals to pass an electric current.

Bondingpages 526

Some types of bonds, such as hydrogen bonds can form without the interactions of electrons. They are bonds caused by attractions between opposite partial charges.

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Hydrogen bonds cause water to exist as a liquid, rather than a

gas, at room temperature.

Now it’s time to identify and build some

COMPOUNDS

Student Exercises: Compounds

In chemistry we use a molecular formula to show how many atoms of each element are present in a molecule. A molecular formula however does not show the structure of the molecule. Scientists often use structural formulas to show the number and arrangement of atoms in a compounds.

Scientists use three different representations to show what molecules look like.

Molecular Models

Methane – CH4 Since carbon's four bonds are usually arranged in space in tetrahedral form,

it is important to have a clear picture of that. This simple fact affects molecular structure as you will soon see. Build a model of CH4, methane.

Its structure looks the same no matter how you turn the model. All of the C-H bonds are single bonds. Note that you can "spin" a H nucleus at the end of its bond without breaking the bond; this is free bond rotation.

http://pirate.shu.edu/~rawncarr/molmodel/methane.jpg

Methane – CH4

In the form of natural gas, methane is regularly distributed via gas pipelines. In many cities, it is piped into homes for domestic heating and cooking purposes. Moreover, large quantities are burned to drive gas or steam turbines, to generate electricity.

Methane in the Earth's atmosphere is an important "greenhouse gas" that contributes to the "greenhouse effect."

http://www.climatechangenorth.ca/images/illustrations/HS_3-4.gifhttp://apps1.eere.energy.gov/state_energy_program/update/images/06-07_greenhouse_effect.jpg

Ammonia – NH3

http://www.alientravelguide.com/science/chemistr/inorgani/ammonia.jpg

www.flickr.com

Sulfuric Acid – H2SO4

http://www.globalwarmingart.com/images/f/f2/Sulfuric_Acid_Molecule_VdW.png

Iron Oxide (Rust) – Fe2O3

www.quantumbase.com

Abscorbic Acid (Vitamin C)

www.microscopy-uk.org.uk

http://www.3dchem.com/imagesofmolecules/vitaminc.jpg

Glucose (Simple Sugar) – C6H12O6

Image:Glucose chain structure.svg

Image:L-Glucose structure.svg

Sucrose (Table Sugar) – C12H22O11

Elements, Compounds, Mixtures

BrainPop Video:

Compounds & Mixtures

hayes8th.blogspot.com

BrainPop Video:

CHEMICAL EQUATIONS

hayes8th.blogspot.com

Balancing Chemical Equations

Being able to balance chemical equations is a vital skill for chemistry.

Tin oxide is heated with hydrogen gas to form tin metal and water vapor. Write the balanced equation that describes this reaction.

Write the unbalanced equation.

SnO2 + H2 → Sn + H2O

* Refer to Table of Common Polyatomic Ions and Formulas of Ionic Compounds if you have trouble writing the chemical formulas of the products and reactants.

http://chemistry.about.com/cs/stoichiometry/a/aa042903a.htm

Balancing Chemical Equations

Balance the equation. • Look at the equation and see which elements are not balanced. In this case,

there are two oxygen atoms on the left-hand side of the equation and only one on the right-hand side. Correct this by putting a coefficient of 2 in front of water:

SnO2 + H2 → Sn + 2 H2O

• This puts the hydrogen atoms out of balance. Now there are two hydrogen atoms on the left and four hydrogen atoms on the right. To get four hydrogen atoms on the right, add a coefficient of 2 for the hydrogen gas. Remember, coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms.

SnO2 + 2 H2 → Sn + 2 H2O

• The equation is now balanced. Be sure to double-check your math! Each side of the equation has 1 atom of Sn, 2 atoms of O, and 4 atoms of H.

http://chemistry.about.com/cs/stoichiometry/a/aa042903a.htm

Changes in Matter

Liquid Nitrogen Experiment

Polymers

Learn about the new self-healing materials being developed at NASA. See how these polymers snap back after impact while the structural integrity of the material remains intact. Find out how scientists use math to calculate

tensile strength.

Real World Self-Healing Materials

Learn about the everyday applications of polyimide foam, one of NASA's commercial inventions of the year. This low-density foam

can be used as a fire-resistant insulation for ships or to reduce airplane noise

Real World: NASA Inventions - Polyimide Foam