Day 14

Instructional Day: 14

Topic Description: This lesson provides an introduction to the concept of variables.

Objectives:

The students will be able to:

• Explain the concept of variables.

• Create examples of variables.

• Explain the concept of iteration.  Create examples of iteration.

Outline of the Lesson:

• Finish Presentations (25 minutes)

• Journal Entry (5 minutes)

• Make Variable Example (15 minutes)

• Enhance Variable Example (10 minutes)

Student Activities:

• Finish Presentations.

• Complete journal entry.

• Participate in a discussion of the Make Variable example.

• Enhance the variable example.

Students will do the following:

1. Use Variables to create a game that awards point for eating health food and subtracts points for eating unhealthy foods. Use this link to see an example of the game: Link to program: https://scratch.mit.edu/projects/46233362/

• Finish Presentations o Have students fill out Peer Grading sheet.

o To help students vote on the best, you may need to do a quick recap of the stories. You may also want to quickly replay some of the better ones.

o Another option is to have students pick the best of each day and do a run off just replaying the top 3 from each day.

• Journal Entry: What does the word variable mean in both mathematical and English terms? o Time the students so they work 3 minutes individually and 2 minutes sharing with their elbow partners.

• Make Variable Example o Give two math examples. x + 3 = 5, 2x = 12

§ Ask: What is the name of the variable here? (Answer: x)

§ Although you have x in both equations, its value varies: it is 2 in one equation and 6 in another.

§ The notion is the same in a program—a variable is a name that represents a value that can be changed. In the math example, the name was x.

o Make the variable example with the students (variable example.sb) having the students help you and build their own at the same time. A possible sequence might be

§ Start by explaining that you want to make a game where you earn points for picking healthy foods and lose points for picking unhealthy ones.

• What do you think the variable will be? If no answer, ask what name will represent a number that will change? (Answer: Points (or Good Nutrition Points in the example))

§ Add the sprites for the banana, cheesie poofs and text that says “Click on food to eat it”. § Ask: What tab do you think you should click on to make a variable? (Answer: Variables.) § Click “make a variable” calling it Good Nutrition Points.

• Clicking the checkbox next to the variable will show or hide it.

§ Ask: If I want to make my points increase by 1 every time I choose the banana, how would I write that script? (See example.)

• Explain that this is an example of iteration.

§ As: How about making the points decrease by one when I click on the cheesie poofs? (See example.)

§ Ask: What do you think should happen when the green flag is clicked? (Answer: reset the points

to 0.)

• Ask: How do you think we should do that? (In example the script for this is under

Sprite4) o Ask: Does it matter which script the “when green flag clicked” is under? (Answer: No.)

• Explain that this is an example of initialization.

• Enhance Variable Example o Have Students enhance the variable example by

§ Adding a food that is worth 2 points when clicked on.

§ Adding a food that is –3 points when clicked on.

Resources:

• Peer Grading