Sink or Float: Discovering Displacement!

Science Grades 2nd Grade 3:53 Video
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Lesson Description

Learn why heavy ships float using the concept of displacement! Join Jessi and the Giant Squid to explore how objects push water aside and how that affects whether they sink or float.

Video Resource

Why Do Ships Float?

SciShow Kids

Duration: 3:53
Watch on YouTube

Key Concepts

  • Displacement: When an object pushes water aside.
  • Buoyancy: The ability of an object to float.
  • Density: How much something weighs compared to how much space it takes up.

Learning Objectives

  • Students will be able to define displacement in their own words.
  • Students will be able to explain why some objects float while others sink, relating it to displacement.
  • Students will be able to predict whether an object will sink or float based on its shape and how much water it displaces.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students if they've ever wondered why big ships can float. Introduce the SciShow Kids video 'Why Do Ships Float?' and explain they will learn about displacement.
  • Video Viewing (5 mins)
    Play the SciShow Kids video 'Why Do Ships Float?' (https://www.youtube.com/watch?v=CvWrkxzCiaY). Encourage students to pay attention to the definitions of displacement and how it relates to floating.
  • Discussion (5 mins)
    After the video, facilitate a class discussion about what they learned. Ask them to explain what displacement means and how it helps ships float.
  • Sink or Float Experiment (15 mins)
    Conduct a simple sink or float experiment. Provide a tub of water and a collection of small objects (e.g., rock, cork, small ball, paper clip, small piece of aluminum foil). Have each student predict whether each object will sink or float BEFORE testing. After testing, discuss the results and why some objects floated while others sank. Emphasize the relationship between the object's shape and its ability to displace water.
  • Shape Challenge (10 mins)
    Give each student a small piece of aluminum foil. Have them crumple it into a ball and test if it sinks or floats. Then, have them reshape the foil into a boat shape and test again. Discuss why the boat shape allows the foil to float (more surface area displacing more water).
  • Wrap-up (5 mins)
    Review the key concepts of displacement and buoyancy. Ask students to give real-world examples of things that float and explain why they float using what they've learned.

Interactive Exercises

  • Sink or Float Prediction
    Students predict whether various objects will sink or float before testing, then compare their predictions with the actual results.
  • Aluminum Foil Boat Challenge
    Students reshape a piece of aluminum foil to make it float, demonstrating how shape affects displacement.

Discussion Questions

  • What does it mean to displace something?
  • Why do some things float, and some things sink?
  • How does the shape of an object affect whether it floats or sinks?
  • Can you think of other things that float because they are shaped to displace water?

Skills Developed

  • Observation
  • Prediction
  • Critical Thinking
  • Problem-solving

Multiple Choice Questions

Question 1:

What is it called when an object pushes water aside?

Correct Answer: Displacement

Question 2:

If something is heavy, will it always sink?

Correct Answer: No

Question 3:

What part of a ship helps it float?

Correct Answer: Its shape

Question 4:

What is the name of the squid in the video?

Correct Answer: Squidstravaganza

Question 5:

A boat is wide and has empty space inside. What does this help it do?

Correct Answer: Float better

Question 6:

What happens when you get into a bathtub full of water?

Correct Answer: The water spills out.

Question 7:

What does Jessi use to demonstrate displacement in the bathtub?

Correct Answer: A toy boat

Question 8:

According to the video, where does the Giant Squid live?

Correct Answer: In the ocean

Question 9:

What does it mean if something is buoyant?

Correct Answer: It can float

Question 10:

What is inside a ship that helps it to float?

Correct Answer: Empty Space

Fill in the Blank Questions

Question 1:

When something pushes water aside, it's called ______.

Correct Answer: displacement

Question 2:

A ship can float because it is designed to _______ a lot of water.

Correct Answer: displace

Question 3:

The shape of an object can help it to _______ in water.

Correct Answer: float

Question 4:

Ships have lots of _______ space inside to help them float.

Correct Answer: empty

Question 5:

Heavy things can float if they ________ enough water.

Correct Answer: displace

Question 6:

Jessi likes to clean herself by soaking in a ________.

Correct Answer: bathtub

Question 7:

The amount of water that spills out when you put something in is equal to the amount of _________ the thing takes up.

Correct Answer: space

Question 8:

The Giant Squid was grumpy because a noisy __________ was floating over him.

Correct Answer: cruise ship

Question 9:

Things that can float can be called __________.

Correct Answer: buoyant

Question 10:

Ships are _______, so they can push aside a lot of water.

Correct Answer: wide

Educational Standards

2.PS1.1:[Standard] Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties. 2.PS1.2:[Standard] Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for the intended purpose.*

Teaching Materials

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