Lesson 15: For Loops with Bee

Overview

Featuring Bee, this lesson focuses on `for` loops and using an incrementing variable to solve more complicated puzzles. Students will begin by reviewing loops from previous lessons, then they'll walk through an introduction to `for` loops so they can more effectively solve complicated problems.

Purpose

Today's concept, `for` loops, are a very important topic in computer science. Not only are they widely used, the process of learning `for` loops enhances the learning of other important concepts (such as variables and parameters.) Students will have plenty of practice critically thinking through problems by determining the starting, ending, and stepping values for each `for` loop. This concept uses plenty of math as well, so feel free to pair it with a math lesson for an even deeper learning experience.

Objectives

Students will be able to:

• Determine starting value, stopping value, and stepping value for a `for` loop.
• Recognize when to use a `for` loop and when to use other loops such as `repeat` and `while` loops.

Preparation

• Play through the puzzles to find any potential problem areas for your class.
• Make sure every student has a journal.

Heads Up! Please make a copy of any documents you plan to share with students.

Vocabulary

• For Loop - Loops that have a predetermined beginning, end, and increment (step interval).

Teaching Guide

Warm Up (15 min)

Introduction

Remind students of the work they did in "For Loop Fun". Open a discussion about what they learned, why they think it might be useful, and if they had any fun. Here are some discussion starters.

• What did you learn in "For Loop Fun"?
• What are the three main components of a `for` loop?
• starting value, step interval, ending value
• Why do you think a `for` loop might be helpful in programming?
• Many students might not know an answer to this. Let them hypothesize, but don't dwell on this question for too long.
• Did you have fun learning about `for` loops? Why or why not?
• Are you excited to use `for` loops in online puzzles?

Bridging Activity - For Loops (15 min)

This activity will help bring the unplugged concepts from "For Loop Fun" into the online world that the students are moving into. Choose one of the following to do with your class:

Unplugged Activity Using Paper Blocks

Split up the students of your class into pairs. Ideally have the pairs be the same from when your class did "For Loop Fun". Print out a `for` loop from Unplugged Blocks (Courses C-F) - Manipulatives for each pair of students. Pass out one die to each pair. Have the partners take turns rolling the die to obtain the following values:

• One roll for the starting value
• Four rolls for the ending value
• One roll for the step value

Have each pair fill in the `for` loop with the appropriate values in the correct spot.

Using a basic number line, like the one used in "For Loop Fun", have the students mark the beginning, ending, and middle values that this `for` loop will touch. When everyone is done, see who got the most points by totaling the starting, middle, and ending numbers of each pair.

Previewing Online Puzzles as a Class

Display a puzzle from the lesson. We recommend puzzle #4 because it displays a potential solution and asks the user to evaluate it.

Using a number line similar to the ones used in "For Loop Fun", mark the start and ending values of the given `for` loop (if you aren't using puzzle #4, you will need to come up with a potential solution first). With the class's help, circle the values between the start and end that the `for` loop will touch. If you are working on puzzle #4, ask the class what they think the answer is to the question, given what they found with the number line.

Main Activity (30 min)

Online Puzzles

Some students may have a hard time differentiating between `repeat` loops and `for` loops. We recommend having scratch paper out for students to make guesses on values like the start, stop, and step. Implementing pair programming amongst the class might also be helpful for your students.

Wrap Up (15 min)

Journaling

Having students write about what they learned, why it’s useful, and how they feel about it can help solidify any knowledge they obtained today and build a review sheet for them to look to in the future.

Journal Prompts:

• What was today’s lesson about?
• How did you feel during today’s lesson?
• How is a `for` loop different from a `repeat` loop?
• Why do you think `for` loops could be useful?
• Practice
• 1
• 2
• (click tabs to see student view)
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Student Instructions

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Student Instructions

Write the code to help the bee collect all of the nectar.

You will need lots of blocks for this challenge, but we'll learn an easier way in the next puzzle.

• For Loops and Repeat Blocks
• 3
• (click tabs to see student view)
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Student Instructions

• Prediction
• 4
• (click tabs to see student view)
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Student Instructions

Ah! The use of `for` loops makes this puzzle a lot easier!

Read the code below. What will happen when you click "Run"?

The bee will move forward and collect all of the nectar from every flower.

The bee will move forward and collect all of the nectar from every flower, except for one.

The bee will move forward and collect one nectar from each flower.

I don't know.

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Student Instructions

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Student Instructions

You can also use a `for` loop to count down.

Try gathering this nectar by counting down from 5 to 1 by 1.

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Student Instructions

The last number in your `for` loop is called the "increment". Each time the loop is run, the counter variable changes by the value of the increment.

Try collecting these flowers using an increment of 2.

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Student Instructions

You've got this!

What should your increment be to collect 3, 6, 9, 12, 15 nectar?

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Student Instructions

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Student Instructions

Now, let's combine the `counter` variable with a `math` block!

How can you use the `counter` variable to navigate this garden with the fewest number of blocks possible?

• Challenge
• 11
• (click tabs to see student view)
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Student Instructions

Challenge: Take what you've learned about `for` loops and try to solve this problem.

Remember: You may have to run through solutions multiple times before you figure out all of the steps.

• Practice
• 12
• (click tabs to see student view)
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Student Instructions

If your loop is counting down, the increment is subtracted from your counter variable each time through.

What should your increment be to collect 15, then 12, then 9, 6, 3 nectar?

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Student Instructions

You can use this `for loop` to collect all of the nectar. Un-bee-lievable!

There are a few actions that you will want to `repeat 'counter' times`.

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Student Instructions

Solve this puzzle with the fewest number of blocks possible.

Standards Alignment

CSTA K-12 Computer Science Standards (2017)

AP - Algorithms & Programming
• 1B-AP-09 - Create programs that use variables to store and modify data.
• 1B-AP-11 - Decompose (break down) problems into smaller, manageable subproblems to facilitate the program development process.