Demonstrating an Exothermic Reaction

See how mixing 2 household items cause heat to be generated

Topics: Chemical Reactions

Age Group: Middle School

Materials:

1. Sodium Hydroxide (also known as caustic soda or Lye) : 5 teaspoons

2. Aluminum foils : 10-15 small strips of aluminum foil

3. Water : 1 cup1 cup of water

4. Test tube with a stopper with a hole in it

5. Thermometer

6. Small balloon

Procedure:

1. Add the Sodium Hydroxide to the test tube and add water till slightly more than half of the test tube is filled.

2. Put the balloon on top of the stopper, so it can collect the Oxygen released

3. Measure the temperature of the test tube using the thermometer and make a note

4. Add the Aluminum foil to the test tube and immediately close the test tube with the stopper

5. You can notice the Aluminum reacting the Sodium Hydroxide and water and the Aluminum dissolving in the water,

6. The balloon will start expanding, with the Hydrogen produced from the reaction along with water vapor, since the water is getting hot

7. Measure the temperature and note the new temperature

Here is a video of this experiment

How It Works:

Aluminum is an amphoteric metal. An amphoteric metal reacts with both acids and bases to create products. There are 5 amphoteric metals, Be (Beryllium), Al(Alumunium),Zn (Zinc), Sn (Tin) and Pb (Lead) .

Aluminum reacts with Sodium Hydroxide and water to form Sodium Aluminate and Hydrogen Gas and this is an exothermic reaction releasing lots of heat.

The reaction is as follows

This kind of reaction where heat is released is called an exothermic reaction. Every Chemical has an associated chemical energy which is the energy required to maintain the bonds between the various atoms of an element or a compound. An exothermic reaction happens because the total energy of the products is less than the total energy of the reactants. A typical exothermic reaction is when you light a gas stove. Natural gas is composed mainly of Methane (CH4). Methane reacts with Oxygen in the atmosphere producing Carbon Dioxide and water vapor and lots of energy in the form of heat.

Endothermic reactions, on the other hand, are those that will absorb heat from the surroundings. One example is the common ice pack that we use for applying to sprained knees. The ice pack is usually comprised of a pouch of Ammonium nitrate kept inside a pouch of water. When we press the ice pack, the pouch inside is crushed, making the Ammonium Nitrate mix with water forming Ammonium and Nitrate ions as shown below

To complete the reaction, it absorbs heat from the surroundings resulting in the ice pack becoming cold to touch.

Another example of an endothermic reaction is Citric acid and Baking soda in water.