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Upper Elementary

Computer Science

Introduction to Conditionals

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Objective

  1. Students will be able to explain what a conditional is in programming.
  2. Students will be able to create a program that uses if/then blocks in Scratch.

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Conditional: A command that tells a program how to make a decision if something is true or false

Vocabulary

?

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Boolean: A value that can only be true or false

Vocabulary

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Review

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How do you decide whether to wear a jacket to school?

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How do you decide whether to wear a jacket to school?

  • Is it cold outside?
  • Is it rainy?
  • Is it cold in the classroom?

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How do you decide whether to wear a jacket to school?

You make a decision based on if conditions are true. If it’s cold, you wear a jacket. If it’s not, you don’t.

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Conditionals in Programming

In programming, we use conditionals to help computers make decisions. A conditional is based on a condition that is either true or false.

Is it cold?

Yes/True

No/False

A value that can only be true or false is called a boolean.

wear jacket

don’t wear jacket

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Here’s an activity to practice conditionals in everyday life.

We use conditionals to make decisions all the time.

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Let’s make some decisions with conditionals!

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Complete the sentence:

If it’s raining, __________.

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Complete the sentence:

If it’s hot outside, __________.

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Complete the sentence:

If my room is messy,

__________.

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Using conditionals in Scratch.

Find the "if/then" block in the Control section.

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Using conditionals in Scratch.

The condition goes in the diamond space.

Use the blue Sensing blocks to check the condition.

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Using conditionals in Scratch.

If the condition is true, the blocks inside the "if/then" block will run.

Is the sprite touching this specific color?

Yes/True: Say “I like purple.”

No/False: Do nothing.

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Using conditionals in Scratch.

Important note: the computer only checks the condition once.

What do we use if we want to repeat a command multiple times?

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Using conditionals in Scratch.

Adding a “forever” loop around the conditional will keep the code running inside of it until the program stops.

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We will make a beach scene program with conditionals!

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Guided Practice

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Program the cat sprite to move.

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Add an “if/then” conditional.

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Add a “touching color” block.

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Add a “say” block to show when the condition is true.

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Test your program.

  • Is your code working as expected?

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  • What changes could be made to your code?

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Add a “forever” loop.

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Program the cat to say “Let’s Play” if touching the Karel sprite.

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Independent Practice

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Add more to the beach scene.

  • Add a new sprite to the scene.
  • Add a conditional for the cat sprite to do something if touching the new sprite.
  • Add a conditional that has the cat sprite do something if it touches another color in the beach scene.

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Extensions

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If you have more time…

  • Add more sprites to the scene.
  • Add a conditional for the new sprite to do something if touching other sprites.
  • Add a conditional that has the new sprite do something if it touches another color in the beach scene.

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Showcase!

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Reflection

Can you give an example of a conditional from our lesson?

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Can you think of other situations in your daily life where you use if/then logic?