Astudent performs the following experiment.
step 1: she pours a colorless solution into a beaker that contains another colorless liquid. yellow particles appear in the liquid.
step 2: she lets the yellow particles settle in the beaker and then separates the colorless liquid by decantation.
what has most likely occurred in the beaker?

Two different changes have occurred in the beaker. The description of the step 1 suggests that most likely a chemical change has occured while the description of the step 2 correspond to a physical change.

Explanation:

When the mixture of two liquid colorless substances results in the appearance of solid particles you first thing in the appareance of a new substance. If this is the case, it means that the original substances reacted chemically to form a new product, so this is a chemical change.

On the other hand, the second step describes just a physical change as it has been just that the yellow particles settled and then a physical separation by decantation. Decantation does not change the chemical properties of the particles settled, they are jsut separeated from the liquid. During this step both the yellow particles and the liquid in the beaker keep their chemical properties, so this is just a physical change.

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"