"When you pulled the steel wool apart, you found that the mass was unchanged. When you heated the steel wool, you found that the mass changed. Explain."

A little short on specifics but I suppose you separated the steel wool by pulling (a physical process which doesn't change the mass) but heat it (I suppose it caught on fire) and this caused oxidation so it changed mass because oxygen was added.

The mass was unchanged when the steel wool was pulled apart because it has the same number of properties split in two. The mass changed when the steel wool was burnt because when the fire heated up the steel wool, oxygen got caught inside the openings of the wool and closed it.

The mas was changed when burnt because the fire heated the wool which allowed oxygen to get trapped. We see this as a chemical reaction because it changed colors and texture.

When you pulled the steel wool apart, you noticed that the mass stayed the same. This is because the mass of an object is determined by the total amount of matter it contains. When you separate the steel wool into smaller pieces, you are not removing or adding any matter, just redistributing it. Therefore, the total mass of the steel wool remains unchanged.

However, when you heated the steel wool, you observed a change in its mass. This is due to a process called oxidation. When metals like steel are heated in the presence of oxygen, a chemical reaction occurs, resulting in the formation of a metal oxide. In the case of steel wool, this process causes the iron in the steel to react with oxygen from the air, forming iron oxide.

The formation of iron oxide is responsible for the change in mass. Iron oxide has a different molecular structure and composition than the original steel wool. During the oxidation process, oxygen atoms combine with iron atoms, resulting in an increase in the overall mass of the steel wool. Therefore, when you measure the mass of the steel wool after heating, it will be greater than its original mass.

It's important to note that in a closed system, the total mass of the steel wool and the surrounding air should remain the same. While the steel wool gains mass due to the formation of iron oxide, there may be a corresponding decrease in the mass of the air molecules that interact with the steel wool. However, these changes in the masses of individual components do not affect the total mass of the system.

When you pull the steel wool apart there wasn`t changed the mass

the mass changed because he put the matches on the steel wood he burn the steel wood is end or slow