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Unit 1 Lesson 3 Substances & Their Properties Lesson ReviewMain Ideas

Read each item. Then select the letter next to the best answer.

1. Alkanes are a group of molecules made entirely from carbon and hydrogen atoms. They have many uses;butane (C4H10) is used in gas stoves and octane (C8H18) is used in car gasoline. A scientist is interested inseeing if the properties of alkanes depend on their size. She experimentally determines the boiling points forthe first eight alkanes, as shown in the graph provided below.

Which of the following conclusions is best supported by the data in the provided graph?

A. The more carbon atoms in an alkane, the lower its boiling pointB. The more carbon atoms in an alkane, the higher its boiling pointC. The number of carbon atoms in an alkane does not affect its boiling pointD. There is not enough information in the provided graph to make a conclusion

2. A pharmacist is preparing aspirin, which is made of acetylsalicylic acid molecules, for a patient who recentlysuffered a heart attack. However, he mistakenly mixes up the labels on various pill bottles and can no longertell which bottle contains aspirin. He decides to set up an experiment to determine which bottle containsaspirin.

Which of the following properties should he test for in his experiment?

A. Color, because aspirin pills are white.B. Mass, because aspirin pills have a specific mass.C. Shape, because aspirin pills have a unique shape.D. Melting point, because aspirin pills melt at a specific temperature.

Think Like a Scientist

Read about each scientific investigation. Then answer the questions that follow the investigation by selectingthe letter next to the best answer.

Investigation A

Two students are interested in seeing how the solubility of sugar and salt in water can be affected by thetemperature of the water. For their experiment, each student measures six 100 milliliter samples of water atthe following temperatures: 0℃, 20℃, 40℃, 60℃, 80℃, and 100℃. The first student measures how manygrams of sugar can be dissolved in his six samples of water, while the second student measures how manygrams of salt can be dissolved in her six samples of water. They then plotted their data on the graph shownbelow.

3. A student on vacation has the opportunity to visit a historic copper mine that is rich in “native copper,” or purecopper found in nature. He takes a piece of native copper from the mine and observes that although it looksvery different, native copper behaves very similarly to the copper wire that he used in a laboratory experimentfor his science class. For example, they both melted at the same temperature.

Which statement best explains why native copper and copper wire behave similarly even though they lookdifferent?

A. They are the same substance, so they have the same composition and properties.B. They are the same substance, but they have different composition and properties.C. They are different substances, but they have similar composition and properties.D. They are different substances, so they have different composition and properties.

4. Based on the provided graph, how does the solubility of sugar and salt change as the temperature of waterincreases?

A. The solubility of both increase, but sugar’s solubility increases more than salt’s.B. The solubility of both increase, but salt’s solubility increases more than sugar’s.C. The solubility of sugar increases, whereas the solubility of salt decreases.D. The solubility of salt increases, whereas the solubility of sugar decreases.

5. Dry clay and sugar have similar densities. However, two layers form when dry clay and water are mixed,whereas only one layer is observed when sugar and water are mixed. Which statement best explains whyclay and water form two different layers?

A. Clay particles are soluble in water.B. Clay particles are not soluble in water.C. Clay and water have similar densities.D. Clay and water have different densities.

6. Based on the provided graph, approximately how many grams of sugar and salt can be dissolved in 100milliliters of water at 20℃?A. 40 grams of sugar, 40 grams of saltB. 200 grams of sugar, 200 grams of saltC. 40 grams of sugar, 200 grams of saltD. 200 grams of sugar, 40 grams of salt

7. To make lemonade, a student adds sugar to a mixture of lemon juice and water. She notices that initially, allof the sugar dissolves immediately. She then notices that after adding several spoons of sugar, the sugarstops dissolving. She tries stirring the mixture, but the sugar still will not dissolve. Her grandmother fixes theproblem by adding more water to the mixture, which causes the sugar to continue dissolving again.

Based on these observations, which of the following most likely increased the amount of sugar particles thatdissolved?

A. Stirring the mixtureB. Not stirring the mixtureC. Adding waterD. Removing water

8. While decorating for a family party, a student decides to put floating candles in the backyard fountain.Interested in why the candles can float in the first place, she decides to look at molecular models for candlewax and water.

Which of the following best explains why the candles can float on water?

A. Wax molecules are spaced far apart, making the candles denser than water.B. Wax molecules are packed close together, making the candles denser than water.C. Wax molecules are spaced far apart, making the candles less dense than water.D. Wax molecules are packed close together, making the candles less dense than water.

9. The students have a friend at a different school who they ask to confirm their results by repeating theirexperiment. He repeats their experiment at his own school by using their procedures. However, he issurprised to find that all of his values are higher than the values reported by his friends at the other school.

Which of the following best describes what the third student can do to obtain results that are more consistentwith the data obtained by his friends?

A. Repeat the experiment exactly like beforeB. Repeat the experiment but use less water for each sampleC. Repeat the experiment but use different temperatures for each sampleD. Repeat the experiment but use his friends’ equipment instead of his school’s

Expressing Science Practices, Concepts, and Ideas

Read the directions for each item carefully before constructing your response.

10. The Crime Scene Unit (CSU) at a local police department has been doing an ongoing investigation on arecent burglary. At the scene of the crime, they found an unknown powdery substance covering varioussurfaces. They take several samples back to their laboratory to analyze them and see if they will help in theirinvestigation.

As a junior member of the CSU, you have given the task of writing a report on the various tests andexperiments that will be conducted on the powdery substance in order to determine its identity. Your two-paragraph report should include:• an explanation of what substances are, and the various types of properties that different substances canhave• a description of at least two different properties that could be used to identify the powdery substance, andwhy they can be used

The report should be appropriate for a formal audience, and must include a topic statement, transitionphases, and the science vocabulary from the word bank.

WORD BANKBoiling point Density Flammability Mass Melting point Mixture PropertySolubilitySubstanceVolume

11. Salt water, rubbing alcohol, and vegetable oil are three common liquids. A student wants to determine theirrelative densities, and so performs a series of experiments. The student’s findings are in the table below.

Using the information in the table, write two paragraphs:• In the first paragraph, explain what density is and why it is important to know or what it can be used for.Your explanation should include both atomic and macroscopic-level descriptions about density.• In the second paragraph, make a claim about how the densities of the three liquids compare to each other.Provide evidence from the student’s observations and reasoning to support your claim.