8.5 E Chemical Formulas, Equations, and Reactions

For a laboratory investigation some students put a strip of shiny metal into a beaker of blue solution and then stored the beaker on a shelf overnight. The next morning, the students recorded observations about the metal and the solution in the box below.

• No, because the metal strip was still visible

• Yes, because a new material of a different color formed on part of the metal strip

• No, because the solution stayed blue

• Yes, because the volume of the blue solution stayed the same

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

As part of an investigation, students combined substances in a beaker to observe chemical reactions. They performed two procedures. They measured the mass of each substance before and after each reaction. The table shows their observations.

Assuming the students did not make any careless errors, what likely explains these changes in mass?

• Procedure 1: All the reactants were liquids that evaporated. Procedure 2: A gas was formed as one product, and it escaped into the air.

• Procedure 1: One of the reactants was converted to thermal energy. Procedure 2: All the products were liquids.

• Procedure 1: The reactants were liquids with different densities. Procedure 2: The reactants were combined into only one product.

• Procedure 1: One of the products was a gas that escaped into the air. Procedure 2: A gas from the air reacted with one of the other reactants.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Four boxes are sliding with constant speed before each box experiences an unbalanced force of 8 N. Which box would experience the greatest acceleration when the unbalanced force is applied?

• The box with a mass of 2 kg

• The box with a mass of 4 kg

• The box with a mass of 6 kg

• The box with a mass of 8 kg

Tags

NGSS.MS-PS2-2

The photograph shows mountains in the Andes range in South America.

Which statement describes the geologic process that is most likely responsible for the formation of these mountains?

• They are along a transform plate boundary that is no longer active, so erosion is creating deep valleys.

• They are along a transform plate boundary in which plates are currently moving side by side, causing earthquakes and faults.

• They are along a plate boundary in which plates are currently converging, causing uplift and steep slopes.

• They are along a plate boundary in which plates diverged in the distant past, allowing new rock to build up.

Tags

NGSS.MS-ESS2-2

A chemical reaction in which calcium carbonate, CaCO3, is decomposed results in the production of two simpler compounds.

What mass of calcium carbonate, to the nearest hundredth of a gram, is decomposed in this reaction?

• 97.49

• 49.97

• 42.00

• .42

Tags

NGSS.MS-PS1-5

Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural resources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below.

Which of these provides evidence that a chemical reaction occurs?

• A gas is present.

• The total number of atoms remain unchanged.

• The state of matter remains the same.

• A brown gas is produced.

Tags

NGSS.MS-PS1-2

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes.

• Oxygen is present.

• A new substance is produced.

• Coal is made up of more than one element.

Tags

NGSS.MS-PS1-2

All of the following equations are correctly balanced except -

• .

• .

• .

• .

Tags

NGSS.MS-PS1-5

For an investigation a student poured a blue solution of CuSO4 into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes.

The student inferred that a chemical reaction occured. What evidence supports this inference?

• A dark solid formed on the zinc metal.

• The zinc metal remained silver-colored and shiny.

• The CuSO4 solution turned blue when the zinc metal was added.

• None of these.

Tags

NGSS.MS-PS1-2

Some students in a chemistry lab conducted an investigation in which they added four different solid substances to separate beakers of water. They stirred the mixtures for one minute and then recorded their observations in the table below.

Which substance most likely caused a new substance to be formed when mixed with water?

• Substance 1

• Substance 2

• Substance 3

• Substance 4

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5