4.4 Physical and Chemical Changes

Multiple Choice

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor?

• H--O Bonds break as H--H and H--O bonds form

• Hydrogen bonds between H2O molecules are broken

• Covalent bonds between H2O molecules are broken

• Ionic bonds between H+ ions and OH- ions are broken

• Covalent bonds between H+ ions and H2O molecules become more effective

Multiple Choice

A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

• The mass of the sample decreased, so physical changes occurred as the metal first melted and then boiled out of the crucible.

• The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

• There was nothing for the metal to react with, so only a physical change could have occurred.

• The sample was only heated, so neither a physical nor a chemical change occurred.

Multiple Choice

A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?

• The solution does not change color after stirring.

• The KCl crystals are no longer visible after mixing with water.

• There is a temperature change in the solution during the dissolving process.

• After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

Multiple Choice

The table above summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and X were mixed?

• Measuring the melting point of the mixture of water and X

• Adding another substance to the mixture of water and X to see whether a solid forms

• Measuring and comparing the masses of the water, X, and the mixture of water and X

• Measuring the electrical conductivities of X and the mixture of water and X

Possible Quiz Questions?!?

Multiple Choice

When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O₂(g) is

Responses

• 6

• 7

• 12

• 14

Multiple Choice

A student placed a piece of Zn(s) in a beaker containing CuSO₄(aq). After 45 minutes, the student observed a brown solid at the bottom of the beaker and that the solution had turned from blue to colorless. Which of the following balanced equations best represents only the species that react and the species that are produced in the reaction?

• 2 Zn (s) + CuSO₄ (aq) --> Zn₂SO₄ (aq) + Cu (s)

• Zn (s) + CuSO₄ (aq) --> ZnSO₄ (aq) + Cu (s)

• Zn (s) + Cu²⁺(aq) --> Zn²⁺ (aq) + Cu (s)

• Zn (s) + Cu²⁺ (aq) --> Zn⁺(aq) + Cu (s)

Multiple Choice

A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure?

• A cube of metal was changed into a flat sheet of metal.

• When two liquids at room temperature were combined in a beaker, the beaker became hot.

• When two clear liquids were combined, the resulting mixture was cloudy.

• When a colorless liquid was added to a blue liquid, the resulting solution was yellow.

Multiple Choice

When the equation above is balanced and the coefficients are reduced to lowest whole-number terms, what is the coefficient of H₂O(l) ?

• 1

• 2

• 3

• 4

Multiple Choice

A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

• The mass of the sample decreased, so physical changes occurred as the metal first melted and then boiled out of the crucible.

• The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

• There was nothing for the metal to react with, so only a physical change could have occurred.

• The sample was only heated, so neither a physical nor a chemical change occurred.