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Essential Science for Teachers: Physical Science

Rising and Sinking Interactive Activity: 5-Question Survey

5-Question Survey: Rising and Sinking

The series of questions presented in this activity will help you find out your ideas or your students’ ideas about matter. As highlighted in this video series, when we articulate our misconceptions, we are taking the first step to rectifying them.

Surveying is one of many educational strategies that teachers can use to elicit ideas. Even a brief survey, such as the one presented next, can provide a learning opportunity for students and teachers alike. Students can reveal their misconceptions for the first time as well as open their minds to accepting scientific points of view. Teachers can form a basis for making instructional decisions, whether to validate students’ correct yet unsure ideas, confront student misconceptions, reinforce ideas that are forming, or complement ideas that are accurate but only partial explanations.

When viewing the answers to each of the survey questions, you will also see how others answered the questions.

Before you complete the survey, please identify who you are (pick just one):

I am a teacher. I instruct:
 Grades K-2
 Grades 3-6
 Grades 7-12
 College students


I am a student. I attend:
 Grades K-2
 Grades 3-6
 Grades 7-12
 College


I am a member of the general public


Survey Question 1

You have two, identical, large pans completely filled with water. Into one of these pans you place a small solid block of pinewood. You observe that the block floats. Into the other pan, you place an identically sized and shaped block, but one of solid aluminum. You observe that the block sinks:

The amount of water displaced (pushed out of the pan) is:

 A. greater for the wood.
 B. greater for the aluminum.
C. the same for both.


Survey Question 2

The water displaced by the block of wood in Question 1 has:

 A. a weight equal to the block’s weight.
 B. a volume equal to the block’s volume.
 C. a weight and volume equal to the block’s weight and volume.
D. a weight and volume different from the block’s weight and volume.


Survey Question 3

The water displaced by the block of aluminum in Question 1 has:

 A. a weight equal to the block’s weight.
 B. a volume equal to the block’s volume.
 C. a weight and volume equal to the block’s weight and volume.
D. a weight and volume different from the block’s weight and volume.


Survey Question 4

A container filled to the brim with only water, and an identical container filled to the brim with water in which a block of wood is floating, are each weighed:

Which of the following is true?

 A. The container with only the water would weigh more.
 B. The container with the water and the block of wood would weigh more.
C. Both containers would weigh the same amount.


Survey Question 5

A glass contains water with ice cubes floating in it. The glass is not completely filled. As the ice cubes melt, the water level in the glass:

 A. will go down.
 B. will go up.
C. will not change.


Now that you’ve completed the survey, make sure to read the closer looks, if you haven’t already, to learn more about these topics.

Answer 1

The answer is B: greater for the aluminum. The amount of water displaced by the aluminum block is greater because the volume of the entire aluminum block is displacing water, while only the part of the wooden block that is submerged, which has less volume than the entire block, is displacing water.

Answer 2

The answer is A: a weight equal to the block’s weight.. The water displaced by the wood block has a weight equal to the block’s weight. When an object rises and floats, the weight of the water displaced is equal to the weight of the object.

Answer 3

The answer is B: a volume equal to the block’s volume. The water displaced by the aluminum block has a volume equal to the block’s volume. However, because it sank, the weight of the water it displaces is less than the weight of the block.

Answer 4

The answer is C: Both containers would weigh the same amount. Both containers will weigh the same amount. Because the wood block floats in the water, the weight of water that it displaces is equal to its own weight. So, by putting the floating block in the water, there is a neither a gain or loss of weight.

Answer 5

The answer is C: the water level will not change. Because they are floating, the ice cubes displace a weight of water equal to their own. They also displace a volume of water equal to their submerged portions. When the ice cubes melt, their total volume as liquid water is exactly equal to the volume of their submerged portions as ice cubes. Therefore, they displace no more or less water than they did before.

Another way to say this is that when the ice cubes melt, they sink until they experience a buoyant force equal to their weight; then they stop sinking. This is sometimes called neutral buoyancy, because the melted ice cubes are neither floating nor sinking. At this point they have still displaced a weight of water equal to their weight, but a smaller volume, because water contracts when it melts. Hence, the overall volume of the water plus the melted ice cubes does not increase.

Series Directory

Essential Science for Teachers: Physical Science

Credits

Produced by Harvard-Smithsonian Center for Astrophysics. 2004.
  • Closed Captioning
  • ISBN: 1-57680-749-5

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