Laboratory #2: Indicators of Chemical Change



Name Period Date

Mrs. Jimenez APS

Lab – Indicators of Chemical Change/Reaction

(Obtain online and type up for final assignment)

Introduction

1) What is the difference between a physical change and a chemical change?

2) List the indicators of chemical change that fit into the following categories…

a) New gas formed:

b) Energy released:

c) New solid or liquid formed:

3) What is the definition of a precipitate?

Methods

1 – Obtain a microchemistry plate. Put it on top of a piece of notebook paper so that there is a white bottom for better viewing. Leave some paper on sides and top for labeling purposes.

2 – Being careful not to contaminate any solutions, perform each combination of solutions listed in Table 1 below. When combining, be sure to put 3 drops of column 1 chemical in first and then add 3 drops of column 2 chemical ONLY AFTER you have made observations of chemical 1 alone and chemical 2 alone, especially with respect to color. Use the LARGER microplate holes. Attempt to label each microplate hole (using the notebook paper) so you can go back and make later observations, knowing what is in there!

*** You are sharing the solutions so please only use one set of chemicals at a time and then put them back on the cart or pass them to another group who needs them. Don’t keep them all at your station. You may take a pipette back to your station, but then be sure to later leave pipettes only with their matching solution to avoid contamination.

2b) Obtain a small slice of potato and place it into one of the microplate holes. Drop 3 drops of iodine in another of the microplate holes just so you can make observations of its color. Then place 3 drops of iodine on your potato slice one at a time and observe changes to the iodine/potato if any.

3 – Make sure you have observations of chemical 1 alone and chemical 2 alone and then be sure to include immediate observations of what happens once mixed immediately PLUS whatever happens 2 minutes or more after the combination.

4 – Fill out tables completely with observations and later analysis.

Results

Table #1 – Observations of Initial Chemicals and Combinations

Chemical 1 Initial Chemical 2 Initial Observed

Observations Observations Indicator of

Chemical Change

|Calcium Chloride (6) | |Sodium Carbonate (2) | | |

|Sodium Bicarbonate (1) | |Acetic Acid (3) | | |

|Potassium Chromate (4) | |Copper Sulfate (7) | | |

|Potato | |Iodine (6) | | |

For table #2 below, for indicators of chemical change column, fill in with new color, new odor, fizzing, light release, sound release, heat release, or precipitate formed. (You can choose more than one if more than one were present!) In the last column, give the reason why it is an indicator of a chemical change by noting the category of the indicator as new gas, energy release, or new solid/liquid.

Table #2 – Analysis of Indicators of Chemical Change

Combined Chemicals Indicator(s) of Chemical Change Category of Indicator

|Calcium Chloride + | | |

|Sodium Carbonate | | |

|Sodium Bicarbonate + | | |

|Acetic Acid | | |

|Potassium Dichromate + | | |

|Copper Sulfate | | |

|Potato + | | |

|Iodine | | |

Analysis and Research Questions – Take it further!

1) What is a physical property vs. a chemical property of matter?

2) It is said that a physical change is easily reversibly. Use this idea to explain why dissolving salt (NaCl) into water to make a homogenous mixture (known as a solution) is a physical change and how you would reverse it.

3) Explain why burning paper is a chemical change and what the indicators are that it is a chemical vs. a physical change.

4) When a mixture is created, its parts have been PHYSICALLY combined not chemically. Research the following methods for separating mixtures that have been combined physically and explain briefly how they work.

Filtration:

Distillation:

References

List any references that you used to answer the above questions in APA format. It is not necessary to cite in text above as long as all references are properly listed here below.

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