CHEMISTRY LAB 2.2 -- Chemical Reactions

Types of Reactions: Lab

PURPOSE:To observe and analyze different types of chemical reactions.

INTRODUCTION:

Chemical reactions involve the breaking of bonds and forming of new bonds. They are the hallmark of chemistry—where elements are chemically combined in order to achieve stable compounds. In this activity, students will observe a synthesis reaction and then perform single and double replacement reactions.

  • In a synthesis reaction, two or more simpler substances combine to make a more complex substance.
  • In a single replacement reaction a free element replaces a less active element in another compound, releasing the less active element.
  • In a double replacement reaction one ionic compound is added to another ionic compound. The anions of one compound react with the cations of the other. The result of this reaction can be a precipitate, water or a gas. A precipitate is a solid substance formed during a reaction. In a double replacement reaction, the anion of one compound and the cation of the other compound react to form a substance that is insoluble in the liquid (won’t dissolve in the liquid). This solid is denser than the solution and therefore separates by settling to the bottom.

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PASTE THE SECTION BELOW INTO YOUR NOTEBOOK

MATERIALS:

Solid Fe, S, Cu, NaHCO3

Aqueous solutions of CuSO4, HC2H3O, AgNO3, Na2CO3,

-mineral wool plugs

-pyrex test tube

-test tube stand and clamp

-bunsen burner

-scale

-weigh paper/boats

-scoopulas

-eyedroppers

Demo Procedure—Synthesis Reaction

  1. Watch your teacher combine iron filings and sulfur.

In data table 1, record observations.

Lab Procedure—Single Replacement Reactions:

***Note: After each reaction you must fill in the table in the post-lab analysis section and answer the questions BEFORE continuing to the next step.***

  1. Copper and silver nitrate: Place one piece copperon the plastic sheet. Add 1 M AgNO4 solution until it just covers it(Caution: silver nitrate can turn your skin black when exposed to sunlight). Wait several minutes. Observe the reaction carefully and record all of your observations in the data table below.

Lab Procedure—Double Replacement Reactions: making chalk

***Note: After each reaction you must fill in the table in the post-lab analysis section and answer the questions BEFORE continuing to the next step.***

  1. Calcium chloride and sodium carbonate.Add a pipet full of CaCl2 to the petri dish . Add a pipet full of Na2CO3 to the petri dish.
  2. Sodium bicarbonate and acetic acid: Place a microspatula full of sodium bicarbonate (NaHCO3) on the plastic sheet. Add 5 drops of acetic acid (white vinegar). Record your observations.

DATA AND OBSERVATIONS:

COPY DATA TABLES BELOW INTO YOUR NOTEBOOK

Table 1: Iron and sulfur—Synthesis reaction

Observations:
1. Iron and sulfur
Reaction / Observations
4. Calcium chloride and sodium carbonate
5. Sodium bicarbonate and acetic acid

Table 2: Single Replacement Reactions

Reaction / Observations
2. Copper and silver nitrate
3. Zinc and sodium chloride

Table 3: Double Replacement Reactions

ANALYSIS QUESTIONS:

Directions: Answer the following questions in your lab notebook based on your results.

Synthesis Reaction:

  1. Fe(s) + S(s)  FeS(s)
  • Explain how this is an example of a synthesis reaction:

Single Replacement Reactions:

  1. Cu(s) + AgNO3(aq) Cu(NO3)2(aq) + Ag(s)
  • What happened to the color of the solution?
  • What does the silver look like?
  1. Zn(s) + 2NaCl(aq)  2Na(s) + ZnCl2(aq)
  2. How did this “reaction” appear to differ from the other reactions?

Double Replacement Reactions:

  1. CaCl2(aq) + Na2CO3(aq)→ NaCl (aq) + CaCO3 (s)
  2. What is the nameof the precipitate?

-Why do you not see the other product?

  1. NaHCO3(s) + HC2H3O(aq)  NaC2H3O(aq) + H2CO3(aq) then

H2CO3(aq)  H2O(l) + CO2(g)

  • How did you determine that a reaction took place?

CONCLUSION:

Directions: In your lab notebooks, write a one-paragraph conclusion that summarizes your results and findings. Then explain the importance of chemical reactions. Next, explain how chemical reactions could be applied toreal-world situations. Finally, discuss what could have been done differently to improve results or elaborate on your findings

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Name:______Period: ______

Date Completed: ______Minutes Earned: ______

CHEMISTRY LAB 2.2

Identifying Chemical Reactions

GRADING RUBRIC

Data, Observation, Data Analysis / All data is properly recorded and includes details from each test.
All data tables are set up in a logical, easy-to-read manner. / All data is properly recorded and includes details from each test
Tablesare set up but not entirely easy to follow. / Most data is properly recorded. Some details might be missing.
Tables are set up but not entirely easy to follow. / Data is incomplete.
Data table is not present.
Analysis Questions / All answers are correct.
All answers are thoroughly explained and supported by the experimental data. / 4-5 answers are correct.
Most answers are thoroughly explained and supported by the experimental data. / 2-3 answers are correct.
Most answers are thoroughly explained and supported by the experimental data. / Less than 2 answers are correct.
Conclusion / Answers the purpose of the lab
Summarizes observations clearly.
Connects this lab to real-world applications.
Connects to how this procedure could have been improved or elaborated upon. / Answers the purpose of the lab
Summarizes observations clearly.
Explains connection to real-world applications. / Answers the purpose of the lab
Summarizes observations clearly. / Answers the purpose of the lab

OVERALL LAB: ______/12 ==scaled to ______/3.5

Teacher Demo: Turning Iron into Copper

Science Concept: Iron and copper elements exchange places with each other in a water solution.

Materials:

Test-tube

Rubber stopper

Blue copper sulfate solution (0.1M)

Black iron filings

10 mL graduated cylinder

Directions:

1. Measure 10 mL of the blue copper sulfate solution (0.1 M).

2. Measure out about 4.0 grams of black iron filings.

3. Pour the blue copper sulfate solution into the test tube.

4. Add the black iron filings.

5. Put the stopper in the test tube and shake vigorously.

Introduction:

Did you ever think it would be possible to transform a golf club into shiny copper pennies? Well, lets give this demonstration a shot.

Explanation:

The iron atoms are initially present in the element form. The copper sulfate is the blue solution containing copper ions and sulfate ions, the copper ions gives the solution the blue color. The iron atoms give electrons to make the copper (+2) ions. The iron atoms have now changed into iron (+3) ions. This then produces a solution of iron sulfate, which is the green solution. The copper metal is now in the element form, the reddish-brown copper element in the test tube, is forced out of the solution and coats the iron filings. This is an exothermic reaction, which gives off heat.

Fe metal + Cu+2 ions--> Cu metal + Fe+2 ions (Cu is the red copper metal after the reaction)

Safety:

This is not a harmful reaction, but take the usual precautions.

Disposal:

First carefully pour of the solution into the sink, keeping the solids in the test tube. The solids of copper metal and iron filings must be disposed of in the garbage, not down the sink.

Iron and sulfur reaction

Demonstration and Class practical

This demonstration or class experiment shows theexothermic reactionof twoelements,ironandsulfur, to form thecompound, iron sulfide. The two solids are mixed and heated in a test-tube (or ignition tube). The reaction can be used to illustrateelements, mixturesandcompounds.

Lesson organisation

This reaction can be carried out as a demonstration or class experiment in awell-ventilatedlaboratory provided that the instructions provided here are strictly adhered to.

The reaction can be carried out in borosilicate glass test-tubes as a demonstration or in smaller (ignition) tubes by students. The reaction provides an opportunity to show that the properties of a compound are different from its constituent elements.

The reaction mustnotbe carried out on tin lids in the open laboratory as is suggested in some sources. The sulfur may boil or burn releasing sulfur dioxide which is a TOXICand CORROSIVEgas and may trigger an asthmatic attack.

Chemicals

Iron powder (potential IRRITANT)

Sulfur – finely powdered roll or flowers

Refer to Health & Safety and Technical notes section below for additional information.

Eye protection

Balance (1 or 2 d.p.)

For the demonstration the teacher will need:

Test-tube made from borosilicate glass (e.g. Pyrex)

Bunsen burner

Heat resistant mat

Clamp stand and clamp

Spatulas, 2

Small bar magnet

Watch glass

Filter paper, 2 pieces (or use 2 weighing boats)

Mineral wool (or mineral fibre)

For the class practical each group of students will need:

Prepared ignition tube (Note 1)

Bunsen burner

Heat resistant mat

Test-tube tongs

Read our standard health & safety guidance

Wear eye protection throughout and ensure that the lab is well-ventilated.

Iron powder, Fe(s), (potential IRRITANT) – this can cause severe irritationin eyes because the iron oxidises rapidly in the saline environment - see CLEAPSS Hazcard. Iron powder is preferred to iron filings. If fine sulfur powder is mixed with iron filings, it is difficult to obtain a consistent mix, because the two solids can separate.

Sulfur, S(s) - seeCLEAPSS Hazcard. Roll sulfur or flowers of sulfur should be finely powdered using a pestle and mortar.

Sulfur dioxide, SO2(g),(TOXIC) is formed if the sulfur catches fire - seeCLEAPSS Hazcard.

1Ignition tubes (75 mm x 10 mm test-tubes) should be filled to no more than one-quarter full with the iron – sulfur powder mix (see Procedure notea). 0.2 g of the mixture is sufficient for the effect to be seen. Place a small plug of mineral wool in the mouth of each ignition tube. After the experiment, the iron(II) sulfide is low hazard and can be discarded into the refuse.

Demonstration aPrepare a mixture containing iron powder and sulfur powder in the ratio 7:4 by mass. Do this by weighing out 7 g of iron powder and 4 g of finely powdered sulfur onto separate pieces of filter paper (or use weighing boats). Mix the two powders by pouring repeatedly from one piece of paper to the other until a homogeneous mixture (by appearance) is obtained.

bNote the appearance of the pure elements and the mixture. Demonstrate that iron can be separated from the mixture by physical means. Do this by wrapping the end of a small bar magnet in a paper tissue or cling film, and dipping it into a teaspoon-sized heap of the mixture on a watch glass. The iron will be attracted, but the sulfur remains on the watch glass.

cPlace about 2 g of the mixture into a borosilicate test-tube.

dInsert a plug of mineral wool (mineral fibre) into the mouth of the test-tube. Clamp the test-tube as shown in the diagram.

eHeat the powder mixture at the base of the test-tube – gently at first and then more strongly (use a blue flame throughout). Heat until an orange glow is seen inside the test-tube. Immediately stop heating. Let the students see that the glow continues and moves steadily through the mixture.

fAllow the tube to cool down. At this point the students could carry out their own small-scale version of the reaction.

gOnce cool, it is possible to break open the test-tube to show the appearance of the product, iron(II) sulfide. The test-tube can be broken open using a pestle and mortar. It is advisable to wear protective gloves.

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