Chemical Change and Observation Lab

1586 Words Sep 24th, 2012 7 Pages
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
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What are chemical changes? Give some examples.

Chemical change results in one or more substances of entirely different composition. Chemical change requires a chemical reaction.

• Burning a log of wood

• Mixing an acid with a base, producing water and a salt.

• Photosynthesis

• Oxidation examples: rust or tarnishing

• Combustion

• Rotting of fruit

• Cooking rice

• Explosion of fireworks

• Lighting a match

• Chewing/digesting food

• Burning gas in a stove

• Oxidizing food for energy

• Roasting a marshmallow

5. What evidences of physical changes have you seen in this experiment?

The tearing of the paper towel into strips; The absorption of the liquid into the paper towel strips (experiment k).

6. What evidences of chemical changes have you seen?

Change in color once chemicals were combined (experiments b,c,d,e,f,g,h,j,l); Precipitate formation (experiments g,j,l), and formation of gas bubbles (experiment a).

7. Write balanced chemical reactions for reactions a,f,g, and j above.

a. NaHCO3+HClNaCl+H2O+CO2

f. NaOCl+KINaCl+KIO3

g. 2KI+Pb(NO3)2PbI2+2KNO3

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