Question

evolution of the atomic model
which of the following is the best explanation for the evolution of the atomic model?
a. advancements in technology enabled scientists to infer more details about atomic structure.
b. the atoms themselves have evolved from simple to more complex over the past 200 years.
c. scientists stopped basing models on experimental evidence.
d. scientists attended better universities and therefore gained more knowledge.

1. will and mallory found an unknown substance in the laboratory and performed several tests on it. they summarized their observations in the table shown below. which observation is classified incorrectly?

observation	physical property	chemical property
2. the substance boils at 87°c.	x	x
3. the substance turns orange when acid is added to it.		x
4. the substance floats on top of water.	x

a. observation #1
b. observation #2
c. observation #3
d. observation #4

1. molly and tony ran some tests on an unknown solid in the laboratory. they determined that the solid had a melting point of 181°c and a density of 0.53 g/ml. they also discovered that the solid conducted electricity and bubbled when placed in an acid. which one of their following observations indicates a chemical change?

a. the solid had a melting point of 181°c.
b. the solid had a melting point of 181°c.
c. the solid had a density of 0.53 g/ml.
d. the solid bubbled when placed in acid.
what is the correct molecular formula for the compound represented by the following model?

Explanation:

1. For the question about the evolution of the atomic model, advancements in technology allowing for more detailed inferences about atomic structure is the best explanation as it has been a key driver in the development of atomic models over time.
2. For the observation - classification question, boiling point is a physical property, not a chemical property, so observation #2 is classified incorrectly.
3. For the chemical - change question, a chemical change is indicated by the formation of bubbles when a solid is placed in acid as it implies a reaction to form a gas, while melting point, density, and electrical conductivity are physical properties.

Answer:

1. A. Advancements in technology enabled scientists to infer more details about atomic structure.
2. B. Observation #2
3. D. The solid bubbled when placed in acid.