Rust in a sealed flask

In the picture

1. 1Tight stopper: the flask is a closed system, so no matter can get in or out
2. 2Grey steel wool and air: the reactants, iron and oxygen
3. 3Rust-brown steel wool: the product, iron oxide (rust)
4. 4Pointer in the same place: the total mass has not changed

Examples

• A sealed bottle with vinegar and baking soda weighs the same before and after it fizzes.
• A log burning in the open seems to lose mass, because the smoke and gases escape into the air.

Quiz: Rust in a sealed flask (Age 13)

1. 1

   Steel wool rusts inside a sealed flask. How does the total mass after the reaction compare to the total mass before?

   • It is greater, because rust is a new, heavier substance
   • It is the same, because nothing got in or out
   • It is smaller, because some of the iron was used up
2. 2

   Why does the flask need to be tightly sealed to show that mass is conserved?

   • To keep the steel wool clean and dry
   • So that no matter can get in or out
   • To make the reaction happen faster
3. 3

   What happens to the atoms during a chemical reaction?

   • New ones are created to build the new substance
   • They are rearranged, but none are created or destroyed
   • Some are destroyed when the old substances disappear

The answers, each with its explanation, are in the app. This quiz is free there while the lesson is in the free week.