Baking Soda Weight Loss

Introduction

Baking soda is not only great for cooking; it is also a useful chemical for science projects. You have probably heard about and maybe even used the baking soda/vinegar reaction to make volcanos erupt, shoot bottle rockets up in the air, or to detect acids and bases. However, there are many more chemical reactions that you can explore with the help of baking soda. One of them is called a decomposition reaction, which makes baking soda lose weight! Want to find out how it works? Then try this activity!

Background

Chemicals can undergo many different reactions such as synthesis reactions that create new substances, or combustion reactions in which a substance usually reacts with oxygen and generates energy in the form of heat. Another reaction type is the decomposition reaction, which is the opposite of a synthesis reaction. When a chemical substance decomposes, it breaks down to form two or more separate compounds. Most chemical compounds are pretty stable and do not decompose spontaneously. You have to put in a lot of energy to break their chemical bonds. However, when chemicals are exposed to enough energy, which can be in the form of heat, radiation, electricity or light, they will decompose.   

Decomposition reactions are the reason why some chemicals or prescription medicines are stored in dark glass bottles. Often times, you do not want a chemical to decompose, as it will change its chemical nature. The dark glass reduces the amount of light that reaches the chemical or medicine, and therefore, prevents light-induced decomposition of the chemical.

Baking soda, or sodium bicarbonate (NaHCO₃), is a chemical that can undergo a decomposition reaction when heated. At temperatures above 80°C (176°F), sodium bicarbonate starts to break down into three compounds, forming sodium carbonate (Na₂CO₃), water (H₂O) and carbon dioxide (CO₂). You use this reaction every time you cook and bake. The produced carbon dioxide gas makes baked goods rise! The higher the temperature of the sodium bicarbonate, the faster it will decompose. Only sodium carbonate will remain as a solid product. Both carbon dioxide and water are gaseous, which means that they will disappear into the surrounding air. You can actually measure this loss—get some baking soda and find out how, in this activity!  

Materials

Preparation

Procedure

Observations and Results

Did you see your baking soda lose weight? You should have—at least for the higher temperature at 400°F. For the lower temperature, your baking soda mass after heating was probably the same (or almost the same) as before you put it in the oven. Baking soda starts to decompose at temperatures around 176°F (80°C). However, at these temperatures, the decomposition will be relatively slow. Fifteen minutes in the oven at 200°F is not enough time to significantly decompose the baking soda.

When you increase the temperature to 400°F, the decomposition reaction will happen much faster. Fifteen minutes is enough time to decompose the baking soda into sodium carbonate, water, and carbon dioxide. The gaseous products (water and carbon dioxide) will escape into the air, which is why your resulting product should be significantly lighter than what you put into the oven.

The appearance of the baking soda will not change at both temperatures. Although you make a new product—sodium carbonate—from baking soda during the decomposition reaction, it will still look the same. Both substances are a white powder.

Cleanup

More to Explore

• Thermal decomposition, from BBC Bitesize
• Chemistry for Kids, Chemical Reactions, from Ducksters Education Site
• Equation for the Decomposition of Sodium Bicarbonate or Baking Soda, from ThoughtCo

Credits