Observations - Monroe Career & Technical Institute
Transcript of Observations - Monroe Career & Technical Institute
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