State if a chemical change has occurred. Give a reason for answer. A student mixes 2 unknown solutions together & notices a cloudiness forming.Also Solid purple iodine crytrals are heated...

State if a chemical change has occurred. Give a reason for answer. A student mixes 2 unknown solutions together & notices a cloudiness forming.

Also

Solid purple iodine crytrals are heated slightly & a purple cloud of iodine gas is observed.

When nitric acid is poured onto limestone, bubbling is seen.

Two colourless solutions at room temperature are mixed. After a minute, the temperature of the mixture is 60 degrees Celsius.

 

1 Answer | Add Yours

nessus's profile pic

nessus | High School Teacher | (Level 2) Adjunct Educator

Posted on

1st: A typical high school expt would be to mix two salt solutions. The cloudiness is a PRECIPITATE (a new compound) so this is a chemical change.

2nd: The iodine has SUBLIMED, it has turned from solid into a gas without being liquid first. If you cool the iodine gas it will RESUBLIME back into solid iodine. This is a PHYSICAL change where no new substance is formed.

3rd: The nitric acid is reacting with calcium carbonate to make calcium nitrate, carbon dioxide, and water. New substances are formed - a chemical change.

4th: You would need to know what is being mixed here. It is possible for heat to be made if a chemical or  physical change has happened.

We’ve answered 318,919 questions. We can answer yours, too.

Ask a question