Observations

Indirect Observations – Those observations that we figure out

from direct observations

Direct Observations – Those observations we make ourselves

Observing Milk Consumption

The cafeteria is considering getting rid of milk at lunch. Before they

do, they need to know how many students drink milk each day.

List as many ways as you can to find out how many students drink

milk each day.

Observation Time Cost Accuracy

Direct Lots Expensive High

Indirect Little Cheap Low

Comparing Observations

Chemical Reactions

Lab Activity #1:

Observe the teacher ripping and burning paper and complete the

data table.

Chemical Reaction – Chemical bonds are formed or

broken

Physical changes are not chemical reactions

Evidence of Chemical Reactions

Evidence of chemical reactions

1. Energy is released

2. Precipitate Forms

3. Color Change

4. Bubbles

5. Change is difficult to reverse

Lab Activity #2:

Observe the teacher mixing different materials and complete the

data table.

Variables

Independent (manipulated) Variable – The variable that YOU assign

Dependent Variable – The variable that responds to what you do

1. Does ice melt faster in the sun or shade

2. Will 5 mg or 10 mg of medicine make your

headache go away faster

3. Are diesel or gas engines more fuel efficient

4. Will salt water boil faster than fresh water

Does Mountain Dew wake you up faster than coffee?

_how fast you wake up__ depends on __type of drink_

Chemical Equations

Reactants – “Ingredients” or substance before reaction

Products – Substance after the reaction

Equation – Description of the chemical reaction

Products go on right side of equation

Reactants go on left side of equation

Equations are balanced so you have the same number of atoms on

both sides of the equation

Two Important Chemical Reactions

6 CO2 + 6 H2O C6H12O6 + 6O2

Sunlight

Chlorophyll

6 CO2 + 6 H2OC6H12O6 + 6O2

Reaction Rates

Lab Activity #3: Carry out the following tests

1. Drop a half tablet of alka-seltzer into water and a half tablet

into vinegar

2. Drop a half tablet of alka-seltzer into hot water and a half

tablet into cold water

3. Drop a half tablet of alka-seltzer into water and stir it and a

half tablet into water that is not stirred

4. Drop a half tablet of alka-seltzer into water and a crushed half

tablet into water

Rates of Chemical Reactions

Chemical Reaction – occur when atoms collide

Reaction rates change from increasing or decreasing collisions

1. Nature of reactants

2. Concentration

3. Pressure

4. Temperature

5. Catalysts

6. Agitation

7. Surface Area

Ways of changing reaction rate:

Energy and Chemical Reactions

Lab Activity #4:

1. Place a 25 ml of vinegar and a thermometer in a small glass

beaker

2. Record the temperature

3. Add 10 g of baking soda and observe any changes in

temperature

4. Place a 25 ml of hydrogen peroxide and a thermometer in a

small glass beaker

5. Record the temperature

6. Add 10 g of yeast and observe any changes in temperature

Energy & Chemical Reactions

Endothermic Exothermic

Energy

Few reactions

Requires energy

Reactants have less

energy than products

Majority of reactions

Releases energy

Products have less

energy than

reactants

Breaking

bonds requires

energy

Activation

energy is part

of the reaction

Types of Chemical Reactions

Synthesis Reactions

Combination

Exothermic

Simple to Complex

2H2 + O2 2H2O

Decomposition Reactions

Separation

Endothermic

Complex to Simple

2H2O 2H2 + O2

Replacement Reactions

Elements trade places

Endo or Exo Thermic

i.e. Cl + NaBr Br + NaCl

Combustion Reactions

Synthesis Reaction

Reactant: O2 and some

compound

Product: H2O and CO2

i.e. Burning wood

Acids, Bases, and pH

Base – Anything that produces OH- (hydroxide ions) in water

Acid – Anything that produces H3O+ (hydronium ions) in water

<7 = Acid

7 = Neutral

>7 = Base

pH – Logarithmic measure of H+ ions

Measuring Acids and Bases

1 Mole H+

ions/liter

10-7 Mole H+

ions/liter10-15 Mole H+

ions/liter

Acids BasesNeutral

0 7 14

What’s a Mole

6.02 x 1023

pH

Within organisms, pH must be carefully maintained or death will

result. In order to prevent pH imbalances, buffers are produced to

moderate changes to acids and bases in the body.

The pH of Beans

Lab Activity #5:

Place 10 beans in a 100-ml beaker. Each bean will represent a H+ ion

and the beaker will represent a solution with a pH of 7 (neutral). Now

make a beaker with 1 bean and a beaker with 100 beans. The 1 bean

solution is a pH of 8 (basic) while the 100 beans are a pH of 6

(acidic).

Use the beans to help you answer the questions in your lab packet.

Measuring pH

Lab Activity #6: Acids and Bases

Special paper called litmus paper can be used to estimate the pH of different

substances. Predict the pH (acid or base) of the following substances. Then

test the substances using the litmus paper provided.

Tap Water Soda Water Starch Solution

Vinegar Milk Apple Juice

Cranberry Juice Coffee Tea

Lab Activity #7: Measuring pH

Better results can be obtained using a pH meter. Predict the pH (1-14) of

the following substances. Then test the substances using the pH meter

provided.

Tap Water Soda Water Starch Solution

Vinegar Milk Apple Juice

Cranberry Juice Coffee Tea