MY PBL PROJECT

INTRODUCTION

When water is added to calcium oxide, the amount of heat produced is enough to fry an egg. This is an ideal demonstration when discussing exothermic reactions and heats of reaction, but it is also a fun attention-getter to use anytime. Calcium oxide, lump, is a special formulation that has a lower surface area of calcium oxide and thus reduces the amount of calcium hydroxide present before adding the water. Fresh calcium oxide lump should be hard pebbles that will crack and become soft when exposed to water. The shelf life for calcium oxide is poor—always use fresh calcium oxide for best results. 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

DRIVING QUESTION

What so special about cooking an egg with calcium oxide? Why is it important to add water to the calcium oxide? Does the reaction changes in anyway if water is not add it?

ANSWER 1- Well it shows the reaction of the calcium oxide with water.

ANSWER 2- so that the calcium oxide can react

ANSWER3- Yes! since nothing happens the egg doesn't cook

MATERIALS

• • • Calcium oxide lump 200 g

• Pie pans

• small aluminum,

• Spatula

• Cooking oil or Pam cooking spray

• Wash bottle for water

• Eggs

• Oven mitt or hot pad

PROCEDURE

1. Place about 200 g of calcium oxide lumps in one of the aluminum pans. The amount depends on the size of the lumps. The calcium oxide should form a single, tightly-packed layer on the bottom of the pan.

2. Add 50–100 mL of water to the calcium oxide . Using a wash bottle will distribute the water more evenly.

3. Add a small amount of cooking oil or Pam to the second pan and then place the pan directly on top of the calcium oxide.

4. When the second pan and cooking oil are hot, break open a small egg into the top pan.

5. The egg is ready!

Scientific Principles

This experiment serves to demonstrate the exothermic chemical reaction between water (H20) and calcium oxide (CaO).

When water is added to calcium oxide lumps (quicklime), an exothermic reaction takes place. The heat produced is enough to fry an egg.

Quicklime or burnt-lime is a white, caustic, alkaline crystalline solid at room temperature. It is made by the thermal decomposition of calcium carbonate in a lime kiln. Calcination occurs at temperatures in excess of 825 °C liberating carbon dioxide gas in the process. When cooled, the quicklime will spontaneously react with CO2 and moisture from the air until, after enough time, it is completely converted back to calcium carbonate. That's the reason why it is the main component in cement, plaster and other construction materials.

In this exothermic reaction water was added to calcium oxide (CaO) to produce the hydrate calcium hydroxide [Ca(OH)2] and a large amount of heat (approx. temperature 150 °C) which can cook an egg in a few minutes.

CaO(s) + H2O → Ca(OH)2(s) + heat

Investigation Part

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. Calcium hydroxide is used to treat acidic soils, soften water, and prepare many 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).

CaO(s) + H2O(l) → Ca(OH)2(s) + heat ΔH = ΔHf (products) → ΔHf (reactants) 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

CAN WE USE IT IN OUR DAILY LIFE ?

We can't use this in our daily life since calcium oxide it's dangerous for cooking. Even in the instructions says that do not eat cooking an egg with calcium oxide. Because of vigorous reaction of quicklime with water, quicklime causes severe irritation when inhaled or placed in contact with moist skin or eyes. Inhalation may cause coughing, sneezing, labored breathing. It may then evolve into burns with perforation of the nasal septum, abdominal pain, nausea and vomiting. Although quicklime is not considered a fire hazard, its reaction with water can release enough heat to ignite combustible materials.Although the dangers we do use calcium oxide for many things we used daily like cement calcium oxide is a key ingredient for the process of making cement. Also petroleum industry it works by water detection pastes contain a mix of calcium oxide and phenolphthalein. Should this paste come into contact with water in a fuel storage tank, the CaO reacts with the water to form calcium hydroxide. Calcium hydroxide has a high enough pH to turn the phenolphthalein a vivid purplish-pink color, thus indicating the presence of water. Even in paper ,calcium oxide is used to regenerate sodium hydroxide from sodium carbonate in the chemical recovery at Kraft pulp mills.

Safety Precautions

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

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