Chemistry 2020

A copper wire was cut into pieces and dropped into a test tube contained acid. Bubbles formed immediately, the liquid in the test tube turned green and the pieces of wire were no longer visible. Which most likely happened to the pieces of copper wire?

• The copper wire was chemically changed when it was cut and placed in the acid.

• The copper wire was physically changed when it was cut and placed in the acid

• The copper wire was physically changed when it was cut and chemically changed when it was placed in the acid

• The copper wire was chemically changed when it was cut and physically changed when it was placed in the acid

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

A student lights the wick of a candle and the candle burns for several minutes. The student makes the following observations:

- Observation 1 :The white candle wick turns black as it burns.

-Observation 2: The solid candle wax near the flame transforms into a liquid. Which choice best compares these two observations?

• Observation 1 describes a physical change and observation 2 describes a chemical change

• Observation 1 describes a chemical change and observation 2 describes a physical change

• Each observation describes a physical change

• Each observation describes a chemical change

Tags

NGSS.MS-PS1-2

A scientist pours two liquids into a flask and swirls the flask to combine the liquids. The scientist then places the flask on a laboratory workbench. After a few seconds the liquids separate into layers. How are the contents of the flask classified?

• as an element

• as a compound

• as a heterogeneous mixture

• a homogeneous mixture

Earth’s air is made up of molecules of different gases that are not joined chemically. Which term best describes air?

• as an element

• a compound

• an alloy

• a mixture

What is the difference between a heterogeneous mixture and a homogenous mixture?

• A homogeneous mixture can only be solid and a heterogeneous mixture only be liquid

• In a heterogeneous mixture you can not see the parts however in a homogenous mixture you can

• A heterogeneous mixture is a physical combination however a homogeneous mixture is a chemical combination

• You can see the parts in a heterogeneous mixture however you can not see the parts in a homogeneous mixture

Which provides the best evidence that a chemical reaction has occurred?

• A color change

• Change in state

• Gas formation

• Change in mass

Tags

NGSS.MS-PS1-2

Which is an example of a homogeneous mixture?

• Salad

• Snow globe

• Suspension

• Saltwater

A solid powder is composed of molecules containing silver (Ag), nitrogen (N), and oxygen (O) atoms. All of the molecules are identical. How is the substance best classified?

• Element

• Compound

• Homogeneous Mixture

• Heterogeneous Mixture

Tags

NGSS.MS-PS1-1

A scientist tests a water sample that was collected from a river. The results of the test are described below:

-The water is clear

-The water contains dissolved calcium

How should this water sample be classified?

• Homogeneous Mixture

• Element

• Compound

• Heterogeneous Mixture

A piece of metal is composed of atoms. Each atom in the metal contains 29 protons. How is the metal classified?

• as a compound

• as an element

• as a mixture

• as a solution

Tags

NGSS.MS-PS1-1