STAR Testing Review

Chemical Reactions&

Chemistry of Life

Chemical & Physical Change

Physical Changes: Any change that alters the form, shape, or appearance of a substance but does not change it into a new substance. EXAMPLE: If I were to toss fresh berries

into a blender and make a fruit smoothie- it would still be fruit, just mashed into smaller pieces.

Chemical & Physical Change

Chemical Changes: a change that a substance undergoes where a totally new substance is the result. EXAMPLE: In the magnesium lab, we

burned magnesium and after it’s chemical change the result was magnesium oxide. It was no longer metal!!

Did a chemical reaction occur??

Was light given off? It was chemical.

Was gas released? It was chemical.

Was heat given off? It was chemical.

Was energy released? It was chemical.

Chem vs. Phys Propeties

Chemical Properties- The characteristic of a substance that describes its ability to change into a new substance Example: Burning of Magnesium into MgO

Physical Properties- A characteristic of a substance that can be observed without changing the substance into a new substance Example: Ice Melting, Cutting a piece of

paper

Bonding & Chemical Reactions

In order for a chemical reaction to have taken place, bonds must have been broken and re-created!! Atoms rearrange to create something totally new. Bonds can change from one form to

another; covalently bonded atoms can rearrange to create ionic bonded atoms (like with the Mg lab)

Reactions

Remember, when atoms come together to form compounds, the new compounds produced have different properties than the atoms did before. No exploding salt!!!!

Balancing equations

Due to the conservation of matter, equations MUST be balanced!

Atoms cannot be created or destroyed! Thus, the atoms in the products must

equal the total atoms in the reactantsREMEMBER: The atoms are only being

rearranged!

Let’s try one…N2 + O2 ---> N2O5

2 N 2 N2 O 5 O

We need to balance out the Oxygen first, then the Nitrogen. This gives us…

2N2 + 5O2 ---> 2N2O5

4 N 4 N

10 O 10 O

Let’s do another, for fun!!

Fe + HCl ---> FeCl2 +H2

1 Fe 1 Fe1 H 2 H1 Cl 2 Cl

Fe + 2HCl ---> FeCl2 +H2

One More…

C2H4 + O2 ---> CO2 + H2O

2 C 1 C4 H 2 H

2 O 3 O

C2H4 + 3O2 ---> 2CO2 + 2H2O

Acids, Basesand the pH scale

Acids and Bases

An Acid is a chemical compound, that, when dissolved in water has a pH of less than 7.

Acids taste sour, react with metals and carbonates and will turn blue litmus paper red.

Acids are corrosive- they eat away at other materials.

Acids and Bases

Bases are chemical compounds that, when dissolved in water, have a pH of above 7.

Bases taste bitter, feel slippery and turn red litmus paper blue.

Bases are corrosive- they eat away materials.

Uses for Acids:

Acids are naturally in many of the foods we eat :Tomatoes, lemons, oranges, and even leafy green veggies!

Acids are also used in many fertilizers. Acids can also be found in batteries

Uses for Bases

Cement is made using basesMany cleaning solutions used in the

home are bases (drain cleaner, glass cleaner, bleach, soap)

Bases can also be found in baked goods such as breads, cakes, and cookies!

The pH scale!!!!

The pH scale is a range of values from 0-14 that express the concentration of hydrogen ions in a solution. The more hydrogen ions, the lower the

number on the pH scale.

Acids & Bases: pH scale

Acids range from 0-6Acids have the most amount of

hydrogen ions.Bases range from 8-14Bases have the least amount of

hydrogen ions. 7 on the scale is neutral (neither)

Neutralizing Acids & Bases

The reaction between acids and bases is a called neutralization.

The neutralization of acids and bases depends on the identities, volumes and concentrations of the reactants. Salts will typically form as a result of

acids and bases neutralizing.

Chemistry of Life!

A quick (very quick) introduction!

Carbon! It’s special!

Because of it’s very special ability to combine in any ways with itself and other elements it has a central roll in the chemistry of living organisms!

CHONPS!

Living organisms are made of molecules consisting largely of:CarbonHydrogenOxygenNitrogenPhosphorusSulfur