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Chemisty: Observations of Chemical Change

Autor:   •  June 18, 2011  •  Essay  •  1,031 Words (5 Pages)  •  3,734 Views

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Lab Report 2

Observations of Chemical Changes

Objectives: (1 of 20 points)

The objectives of this experiment are:

1. To observe some properties of chemical reactions

2. To associate chemical properties with household products

Background Information: (2 of 20 points)

Chemical changes are often accompanied by physical changes. Three that you should not see in this lab are changes in temperature, presence of a flame, and evolution of light, as when as firefly glows. Three physical changes that indicate a chemical change may have occurred (and that may be seen in this lab) are:

1. Color changes

2. Precipitate (formation of a solid)

3. Formation of gas bubbles

Procedure: (1 of 20 points)

No preliminary dilution of my test chemicals were necessary as Lab Paq provided pre-diluted chemicals. Utilizing the 96-well plate, 2 pipet drops of each chemical were added to the wells in the following combinations: a) NaHCO3+HCl b) HCl+Bromthymol blue c) NH3+1 drop Bromthymol blue d) HCl+blue dye e) Blue dye+NaOCl followed by HCl f) NaOCl+KI followed by various test foods g) KI+Pb(NO3)2 h) NaOH+phenolphthalein i) HCl + phenolphthalein j) NaOH+AgNO3 k) AgNO3+NH3 l) NH3+CuSO4. Along the way, observations were made pertaining to the reactions witnessed. This experiment concluded with testing household chemicals and proper disposal of lab chemicals. 

Observations: (10 of 20 points)

CHEMICALS Well # Reaction on white paper Reaction on dark paper

a. NaHCO3 + HCl A1 Bubbling Clear Liquid Bubbling Clear Liquid

b. HCl + BTB B1 Golden Yellow Clear Liquid Amber Clear Liquid

c. NH3 + BTB C1 Royal Blue Clear Liquid Dark Blue Opaque Liquid

d. HCl + blue dye D1 Emerald Green Clear Liquid Dark Green Opaque Liquid

e. NaOCl + blue dye E1 Bright blue that dissolved to yellow Same; just easier to see

then to pale yellow.

f. NaOCl + KI F1 Gold clear Liquid; then Black Dark Gold Clear; then Black

after starch added

g. KI + Pb(NO3)2 G1 Bright yellow “puddy-like” Bright

...

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