Identify chemicals based on their uses (recall)

1. Hi! I am a white powder. Doctors use me to support fractured bones.

• Check your answer.

  I am plaster of Paris (${\text{CaSO}}_4.{\displaystyle \frac{1}{2}}{\text{H}}_2\text{O}$‍).

  When mixed with water and applied around the fractured limbs, I become a hard mass and keep the bone joints in a fixed position.

2. Hi! I am a sodium salt. I am added while baking bread and cakes to make them soft and fluffy. If added in more quantity, I make the cake taste bitter.

• Check your answer.

  I am baking soda (${\text{NaHCO}}_3$‍).

  When mixed with water and the flour to make a dough (or a batter), I undergo a chemical reaction and produce carbon dioxide gas. This gas gets trapped into the dough (or a batter) and bubbles out, which causes the cake to rise to make it soft and fluffy.

  I am a base. If added more, I make the cake taste bitter. To neutralize, I mix with tartaric acid. Together, we are called baking powder.

3. Hi! I am a sodium salt. I am present in detergents. I clean all your clothes.

• Check your answer.

  I am washing soda (${\text{Na}}_2{\text{CO}}_3.10{\text{H}}_2\text{O}$‍).

  The sodium carbonate (${\text{Na}}_2{\text{CO}}_3$‍) "softens" water helping other cleaning ingredients lift soil from the fabrics and suspend the soil in the wash water. Now, I bind to the minerals, which makes water hard and allows the detergent to be absorbed into fibers properly to clean clothes.

4. Hi! I am a white powder. I disinfect drinking water. Also, I disinfect swimming pools.

• Check your answer.

  I am bleaching powder (${\text{CaOCl}}_2$‍).

  I release chlorine when mixed with water. This chlorine kills the pathogens like disease-causing bacteria.

5. Hi! I am a sodium salt. When you get acidity, I come to your rescue. I am an antacid.

• Check your answer.

  I am baking soda (${\text{NaHCO}}_3$‍).

  I work as an antacid because I have an alkaline (or basic) pH, which helps to neutralize the acidity in your stomach.

6. Hi! I am a sodium salt. I remove the permanent hardness in water.

• Check your answer.

  I am washing soda (${\text{Na}}_2{\text{CO}}_3.10{\text{H}}_2\text{O}$‍).

  I react with sulphide and chloride salts of magnesium and calcium to form insoluble carbonates, converting hard water to soft water.

7. Hi! I am a white powder. I am used as an oxidizing agent in many chemical industries.

• Check you answer.

  I am bleaching powder (${\text{CaOCl}}_2$‍).

  I react with dilute acids to release chlorine gas, which is a strong oxidizing agent.

8. Hi! I am a white powder. People use me for making toys, decoratives, molds, etc., for making a smooth surface.

• Check your answer.

  I am plaster of Paris (${\text{CaSO}}_4.{\displaystyle \frac{1}{2}}{\text{H}}_2\text{O}$‍).

  When mixed with water, I form a paste. When dried, I become hard into solid structures.

9. Hi! I am a sodium salt. I am present in the fire extinguishers.

• Check your answer.

  I am baking soda (${\text{NaHCO}}_3$‍).

  On heating, I become sodium carbonate releasing water and carbon dioxide.
  ${\text{CO}}_2$‍ is denser than ${\text{O}}_2$‍. So when we spray the carbon dioxide on fire, it sinks under the oxygen, separating the fire from oxygen. No oxygen, no fire!

Summary