Playing with Playdoh Overview Campers will use recycled aluminum foil to create an alum that can act as a coagulant in playdoh. The alum will be prepared from a chemical reaction from the mixture of the aluminum with sodium hydroxide. The products will be filtered, then reacted with sulfuric acid. Once the alum is prepared, it will be added to a few household ingredients to make a fun batch of playdoh!

Topic (s) Chemistry Grade Level 7-9 Cost (per student) $0.70 Time (preparation and activity) 1.5hr Complexity Hard Ontario Curriculum Links

Understanding Matter and Energy: Grade 7 – Pure Substances and Mixtures

Big Ideas: Pure substances and mixtures have an impact on society and the environment.

Specific Expectations Follow established safety procedures for handling chemicals and apparatus (e.g., wash hands after handling chemicals, take note of universal warning symbols) Investigate processes (e.g., filtration, distillation, settling, magnetism) used for separating different mixtures

Chemistry: Grade 9 – Atoms, Elements, and Compounds

Big Ideas: Investigate, through inquiry, the physical and chemical properties of common elements and compounds

Specific Expectations Assess the usefulness of and/or the hazards associated with common elements or compounds in terms of their physical and chemical properties

Chemistry: Grade 10 – Chemical Reactions

Big Ideas: Analyse a variety of safety and environmental issues associated with chemical reactions, including the ways in which chemical reactions can be applied to address environmental challenges

Page 1 of 6 ESQ Activity Write-Up 2009 Playing with Playdoh Specific Expectations: Analyse, on the basis of research, various safety and environmental issues associated with chemical reactions and their reactants and/or product(s)

Theory & Background Information Recycling Aluminum Aluminum is the third most common element and the most abundant metal on the Earth’s crust. Partly for this reason, it is widely used by industrialized societies. However, its production from raw materials is highly energy intensive. Since aluminum is not oxidized easily, an aluminum can could remain for more than 100 years along the side of the road. Nearly 100 years ago, scientists believed that each person disposed of roughly 3 pounds of garbage every day. In today’s society, it is estimated that each person produces around 5 pounds of garbage per day. It is easy to see why it is so important to recycle this important metal. When aluminum cans are prepared from recycled material, only 5% of the energy is used compared to preparing them from original raw material. It should be noted that the process of recycling aluminum we will be doing today is not the same as the industrialized one – as it is too expensive on the large scale. It is just a representation of the recycling of aluminum.

Chemistry of the Experiment Several chemical reactions will take place during this activity. A chemical reaction is the process of creating a new product from some set of reactants. Chemical reactions are irreversible, while physical reactions can easily be reversed. Signs of a chemical reaction include: a colour change, a new scent, a phase change (ex. gas bubbles or a precipitate), and a release of heat. (Campers need not understand the following set of reactions, but a brief summary is given for leaders) Solid aluminium is first dissolved in potassium hydroxide, according to the following balanced chemical reaction (which is a redox reaction – the Al is oxidized and the H reduced): 2 Al(s) + 2 KOH(aq) + 6 H2O(liq) → 2 KAl(OH)4(aq) + 3 H2(g) The solution should now be colourless. An acid-base reaction is performed next, with the addition of sulfuric acid. 2 KAl(OH)4(aq) + H2SO4(aq) → 2 Al(OH)3(s) + 2 H2O(liq) + K2SO4(aq) The acid donates protons to the base (ion of aluminum hydroxide) and forms a thick white precipitate of aluminum hydroxide. When more sulfuric acid is added, the aluminum hydroxide precipitate dissolves, according to the following chemical reaction: 2 Al(OH)3(s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 6 H2O(liq) The solution now contains aluminium and potassium ions, which are crystallized out in the form of aluminium potassium hydrate (KAl(SO4)2•12 H2O) then filtered. The aluminium potassium hydrate is a form of alum. The solution must be cooled because the alum is soluble in water at room temperature. The final chemical equation shows the formation of the alum: Al2(SO4)3(aq) + K2SO4(aq) + 24 H2O(liq) → 2 KAl(SO4)2•12 H2O

Page 2 of 6 ESQ Activity Write-Up 2009 Playing with Playdoh A vacuum filtration apparatus removes all alum from solution. The crystals are washed with an alcohol solution (because water would dissolve the crystals). Alcohol is also more volatile than water, so the crystals dry faster.

Materials Per Camper Safety Materials Gloves Lab coat Safety goggles

Per Group Preparation of Alum 10mL of 6M H2SO4 20-30cm strip aluminum foil Ice bath dish (or large beaker) 250mL beaker Ice 35mL 2M KOH Filtering flask (500mL or so) Glass stirring rod Tubing Thermometer Buchner funnel Hot plate Small filter paper (to fit inside Glass funnel funnel) 11cm filter paper Retort stand 150mL beaker Clamps Wash bottle of water 20mL ethanol Methyl red (10 drops)

Making Playdoh 400mL beaker Water Flour Salt Food colouring Cooking oil Prepared alum Oven mitts

Procedure Preparations Obtain all materials as listed, and ensure all safety features and materials are present Set up the filtration apparatus on the lab bench: o Clamp the filtering flask to the retort stand

Page 3 of 6 ESQ Activity Write-Up 2009 Playing with Playdoh o Attach one end of the tubing to the arm of the filtering flask and the other end to the suction o Place the Buchner funnel with the small filter paper on top of the filtering flask o Ensure that the filtering flask is stable Introduction 1. Ask campers if they know what the most common metal in the earth’s crust is. Explain that it is aluminum, and it is also the third most abundant element (from the periodic table) in the Earth’s crust. Show where metal elements are on the periodic table. 82 of the 106 known elements are metals. a. Ask campers for some characteristics of metals (lustrous, malleable, conductors, opaque, high density, solid at room temperature (except Hg)). 2. Ask campers to guess what mass of garbage the average North American produced one hundred years ago (about 3 pounds) and the amount that we produce today (about 5 pounds each per day). a. Ask campers for ways to reduce their personal garbage output. (Reduce, reuse, recycle.) b. Explain that today, we will be recycling aluminum in tin foil to make alum which can act as a coagulant to make playdoh. By recycling aluminium (such as pop cans), 95% of the energy used to make a pop can from scratch can be saved. i. To recycle our aluminum, we will be using chemical reactions. Explain that each chemical reaction starts with reactants which create new products. ii. Ask the campers if they know any signs of a chemical (irreversible) reaction – heat, phase change, colour change etc. 3. Split camp up into 3 large groups. Ensure that everyone has the proper safety materials (lab coat, goggles, gloves). Each leader will run the experiment with lots of help from the campers. Activity 1. Obtain a large piece of aluminium foil and get one camper to weigh out 0.6-0.9g of it. 2. Get another camper (or two) to cut into small pieces while placing them in a 250mL beaker. 3. LEADER: In a fume hood, add 35mL 2M KOH to the beaker; stir with glass stirring rod (keep beaker in fume hood for duration of reaction). 4. Cool mixture to room temperature (if aluminium has not dissolved, heat over hot plate at low temperature and campers may stir until it is fully dissolved; cool again to room temperature)

Page 4 of 6 ESQ Activity Write-Up 2009 Playing with Playdoh 5. LEADER: fold filter paper to fluted style – fold three times in half then fold into thirds. Filter solution using glass funnel and 11cm filter paper; filter into 150ml beaker (could also use 250mL). 6. Use wash bottle to rinse original beaker with a small amount of water and filter 7. Ask one camper to add 10 drops methyl red indicator to filtered solution (yellow in basic and red in acidic solutions). Make sure the campers notice the colour of solution. Remind them about the properties of an acid-base indicator learned earlier in the week. 8. LEADER: Wearing gloves, measure 10mL of 6M H2SO4 in a graduated cylinder; add small portions slowly to the solution while stirring vigorously (note: only add enough H2SO4 until white lumps of Al(OH)3 appear – not all 10mL needs to be added). 9. Heat solution on hot plate at medium setting, while camper is stirring vigorously until the solution becomes clear; LEADER: add small portions of H2SO4 if white lumps are hard to dissolve. 10. Cool beaker to room temperature, while a camper can lightly stir occasionally. 11. Ask one camper to place the beaker in an ice bath to cool the beaker further. This induces the formation of crystals (scratch bottom of beaker with glass stirring rod if no crystals form after 5min, or borrow a small piece of crystal from another group and place in your beaker). 12. Ask one camper to wet the small filter paper (which fits inside Buchner funnel in suction filtration apparatus) with small portion of ethanol. 13. Filter crystallized solution with suction filtration apparatus (each camper may cover to top of the Buchner funnel with gloved hand to speed up filtration). 14. Ask one camper to wash beaker with 10-15mL ethanol and filter this as well. 15. Ask one camper to dry crystals by pushing down on crystals in Buchner funnel with another small filter paper (if necessary). 16. LEADER: Release suction filtration by first removing hose from side arm flask; then turn off water. 17. Ask one camper to measure 150mL water in a 400mL beaker, then place it on the hot plate to boil. 18. Get campers to measure and mix 125mL flour, 60mL salt and 3 medium sized scoops of prepared alum in a 600mL beaker. 19. Ask campers to add 10mL cooking oil, 120mL boiling water (using oven mitts), and 3 drops food colouring; campers can take turns mixing well and kneading until smooth. 20. Store Playdoh in plastic bag in the fridge and it should last several weeks.

Activity Accommodations and Extensions As an extension, the chemistry of the experiment can be explained (from the Introduction) Since the leaders are the ones mainly doing the experiment and campers are only helping, accommodations are easy to make – don’t let campers do anything they are not capable of

Page 5 of 6 ESQ Activity Write-Up 2009 Playing with Playdoh o The chemistry of the experiment can be excluded and the basic science of the experiment can be explained (what a reaction is etc)

Safety Considerations Addition of 2M KOH creates a violent reaction: o the beaker should be handled by a leader in the fume hood until reaction is complete and solution has cooled to a reasonable temperature o leader should wear gloves, proper eye protection, and a lab coat along with all campers Addition of 6M H2SO4 is hazardous because it is very concentrated and corrosive o Only leaders should handle the H2SO4, and should do so while still wearing all the protective equipment and under the fume hood Leaders should set up the suction filtration apparatus, to ensure that no glassware is broken and that it is set up properly Glassware will be extremely hot after boiling water – wear oven mitts to prevent any burns

Resources http://www.owlnet.rice.edu/~chem122/Lab122/Al/ http://employees.oneonta.edu/kotzjc/LAB/Alum_Expt.pdf

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