The Chef

Demonstration Kit

Introduction

Liven up your lesson plan on chemical reactions with this fun demonstration of chemical and culinary wizardry. Would you believe the amount of heat released when calcium oxide reacts with water is enough to fry an egg? This demonstration provides an ideal introduction to chemical reactions, synthesis reactions and heats of reaction.

Concepts

  • Exothermic reactions
  • Heat of reaction
  • Synthesis (combination) reaction
  • Hess’s law

Materials

Calcium oxide, CaO, 100 g*
Water, distilled
Chef’s hat*
Cooking oil or Pam® cooking spray
Egg, small (medium or large eggs do not work as well)
Graduated cylinder, 100-mL
Oven mitt or hot pad
Pie pans, small aluminum, 2*
Spatula*
Thermometer, digital (optional)
Wash bottle
Weighing dish, large
*Materials included in kit. 

Safety Precautions

Calcium oxide is a corrosive solid and a severe body tissue irritant. Avoid all body tissue contact. Reaction of calcium oxide and water will produce large amounts of heat—skin burns are possible. A lump of calcium oxide may disintegrate violently and splatter when water is added. This should be a teacher demonstration only. Do not allow students to perform this procedure. Food-grade items that are brought into the lab are considered laboratory chemicals and should not be consumed. Do not eat the egg after it is cooked. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information. 

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The solid calcium hydroxide produced in the demonstration may be neutralized with hydrochloric acid and flushed down the drain with excess water according to Flinn Suggested Disposal Method 10.

Procedure

  1. Measure 100 g of calcium oxide into a large weighing dish.
  2. Place one of the aluminum pie pans onto a heat-resistant surface or pad. Using a graduated cylinder, measure and add 40 mL of distilled water to the pan.
  3. Spray the second aluminum pan with cooking spray or add a small amount of cooking oil to the pan.
  4. Quickly but carefully add the calcium oxide to the water in the first aluminum pan. Distribute the calcium oxide evenly across the pan to get efficient contact between the solid calcium oxide and water. Caution: Splattering may occur.
  5. Immediately place the second aluminum pan directly on top of the calcium oxide.
  6. Wait about one minute—steam should be evident emanating from the bottom pan, and the cooking oil or spray may begin to sizzle.
  7. Quickly break a small egg into the top pan. Caution: The pan will be hot. Wear a heat-resistant glove or use an oven mitt to hold the top pan with one hand while gently using the spatula to check the egg with the other hand.
  8. Cook the egg to order! Continue cooking for several minutes—the egg white will continue to cook after the steam has subsided. (The egg white will “fry” but the yolk will remain runny.)
  9. (Optional) Insert a digital thermometer probe directly underneath the top pie pan. Measure and record the temperature. (The temperature will reach a maximum of 110–120 °C.)

Student Worksheet PDF

13922_Student1.pdf

Teacher Tips

  • This kit contains 700 g of CaO, enough to perform the demonstration at least seven times. The chef’s hat, aluminum pans, and spatula are reusable. Order more calcium oxide from Flinn Scientific to repeat this demonstration.
  • The shelf life for calcium oxide is poor—always use fresh calcium oxide for best results.
  • Always use an oven mitt or hot pad to hold the pans when cooking the egg. Place the aluminum pans on a heat-resistant surface—the bottom pan will get very hot. This reaction generates a lot of heat; use proper care handling the pans. Steam burns are very dangerous.
  • Try “scrambling” the egg before adding it to the pan. Use only small or medium eggs.

Correlation to Next Generation Science Standards (NGSS)†

Science & Engineering Practices

Using mathematics and computational thinking

Disciplinary Core Ideas

MS-PS3.B: Conservation of Energy and Energy Transfer
MS-PS3.A: Definitions of Energy
MS-PS1.B: Chemical Reactions
HS-PS3.B: Conservation of Energy and Energy Transfer
HS-PS3.D: Energy in Chemical Processes

Crosscutting Concepts

Energy and matter

Performance Expectations

MS-PS2-5: Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact
HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

Answers to Questions

  1. Write a balanced chemical equation for the reaction of calcium oxide and water to produce calcium hydroxide.Hint: If the solubility of calcium hydroxide in water is only 1.6 g/L, what is the state of the major product?

    CaO(s) + H2O(l) → Ca(OH)2(s) + heat

  2. Use Hess’s Law to express the heat of reaction for this equation in terms of the heats of formation of the reactants and products.

    ΔH = ΔHf (products) – ΔHf (reactants)

    ΔH = ΔHf [Ca(OH)2(s)] – {ΔHf[CaO(s)] + ΔHf [H2O(l)]}

  3. Use the following information to calculate the heat of reaction.
    {13922_Answers_Table_1}

    ΔH = ΔHf[Ca(OH)2(s)] – {ΔHf[CaO(s)] + ΔHf[H2O(l)]}

    ΔH = – 986.1 kJ/mol – (– 635.1 kJ/mol – 285.8 kJ/mol)

    ΔH = – 65.2 kJ/mol

  4. Assuming 100 g of calcium oxide was used in this demonstration and it was completely converted into calcium hydroxide, how much heat was produced?
{13922_Answers_Equation_3}

Discussion

Calcium oxide is also known as lime or quicklime and is used to make plaster, mortar, bricks, and many other construction materials. Calcium oxide is produced by heating limestone (calcium carbonate) in air. However, calcium oxide readily absorbs and reacts with carbon dioxide and water to form calcium carbonate (CaCO3) and calcium hydroxide [Ca(OH)2], respectively. When water is added to calcium oxide, an exothermic reaction occurs, producing calcium hydroxide and a large amount of heat. The combination of calcium oxide and water to produce calcium hydroxide is an example of a synthesis or combination reaction. Calcium hydroxide is used to treat acidic soils, soften water and prepare building materials such as plaster, mortar, and bricks. The solubility of calcium hydroxide in water is very low, about 1.6 g/L. The product of the reaction of CaO and H2O is thus Ca(OH)2(s), not Ca(OH)2(aq) (Equation 1).

{13922_Discussion_Equation_1}
The heat of reaction can be calculated using Hess’s law (Equation 2).
{13922_Discussion_Equation_2}

ΔH = ΔHf[Ca(OH)2(s)] – {ΔHf[CaO(s)] + ΔHf[H2O(l)]}

ΔH = –986.1 kJ/mole – [–635.1 kJ/mole + (–285.8 kJ/mole)] = –65.2 kJ/mole

References

Special thanks to DeWayne Lieneman, retired chemistry teacher, Glenbard South High School, Glen Ellyn, Illinois, for providing Flinn Scientific with the instructions for this activity.

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†Next Generation Science Standards and NGSS are registered trademarks of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.