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Lesson 4: Sequencing in Scratch

Estimated time: 15-20 minutes | Scratch Activity

What You Will Learn

By the end of this lesson, your child will be able to:

Snap Scratch blocks together in the right order to make things happen
Make a sprite tell a short story using "say" and "wait" blocks
Make a sprite move and turn to draw a shape
Understand that Scratch reads blocks from top to bottom, just like a recipe

Scratch Blocks Are Steps

You have been practicing step-by-step thinking with recipes, directions, and flowcharts. Now it is time to use those same skills on the computer! In Scratch, each colored block is one step. You snap blocks together in a stack, and Scratch runs them from top to bottom -- just like reading a list of instructions.

Sequence -- In coding, a sequence is a set of instructions that run in order, one after the other, from top to bottom. Scratch runs the top block first, then the next one, then the next, all the way to the bottom.

Getting to Scratch

Open Scratch in your web browser by going to scratch.mit.edu and clicking "Create." You do not need an account to start coding, but creating a free account lets you save your projects.

You will see the Scratch cat (the sprite) on the right side of the screen. The colored blocks are on the left. You drag blocks into the middle area and snap them together to build your program.

Project 1: Make the Cat Tell a Story

Let us make the Scratch cat tell a short story. We will use blocks from the "Looks" category (purple blocks) and the "Control" category (yellow blocks).

Scratch Blocks to Use

Build this stack of blocks by dragging them from the left panel:

when green flag clicked
say [Hello! My name is Scratch Cat.] for (2) seconds
say [I love to dance and play!] for (2) seconds
say [Want to see me move?] for (2) seconds
move (100) steps
say [Ta-da!] for (2) seconds

How to build it:

Click the "Events" category (dark yellow). Drag "when green flag clicked" to the middle area.
Click "Looks" (purple). Drag "say [Hello!] for (2) seconds" and snap it under the green flag block. Change the text to "Hello! My name is Scratch Cat."
Drag another "say" block and snap it below. Change the text to "I love to dance and play!"
Add another "say" block: "Want to see me move?"
Click "Motion" (blue). Drag "move (10) steps" and snap it below. Change 10 to 100.
Add one more "say" block: "Ta-da!"

Click the green flag above the stage to watch your story play!

Talk About It

After running the project, ask your child: "What would happen if we moved the 'move 100 steps' block to the very top, before the 'say' blocks?" Let them try it and see! The cat would move first and then talk. The order of the blocks changes what happens, just like the order of steps in a recipe changes the result.

Project 2: Draw a Square

Now let us use step-by-step thinking to make the cat draw a square. A square has four sides, so we need to tell the cat to move forward and turn four times.

Scratch Blocks to Use

First, add the Pen extension: click the blue "Add Extension" button at the bottom-left of Scratch, then click "Pen."

when green flag clicked
erase all
pen down
move (100) steps
turn right (90) degrees
move (100) steps
turn right (90) degrees
move (100) steps
turn right (90) degrees
move (100) steps
turn right (90) degrees
pen up

How it works:

"pen down" means the cat leaves a trail as it moves (like putting a marker on paper)
"move 100 steps" draws one side of the square
"turn right 90 degrees" makes the cat turn a corner
We repeat the move-and-turn four times for four sides
"pen up" means stop drawing

Try It: Change the Shape

After drawing a square, challenge your child:

Make a bigger square: Change 100 steps to 150 steps.
Make a triangle: Use only 3 sides and change the turn to 120 degrees.
Make a rectangle: Alternate between moving 100 steps and 50 steps.

Each change shows how adjusting the steps changes the result. This is the power of step-by-step thinking!

Project 3: Simple Animation

Animation is just a series of small changes that happen one after another. You can make the Scratch cat look like it is walking by switching between two costumes.

Scratch Blocks to Use

when green flag clicked
switch costume to [costume1]
move (10) steps
wait (0.3) seconds
switch costume to [costume2]
move (10) steps
wait (0.3) seconds
switch costume to [costume1]
move (10) steps
wait (0.3) seconds
switch costume to [costume2]
move (10) steps

The cat switches between its two built-in costumes (one with legs apart, one with legs together) while moving forward. This makes it look like the cat is walking!

Talk About It

Ask your child: "Do you see a pattern in these blocks?" They should notice that "switch costume, move, wait" repeats over and over. In Module 5, you will learn about loops, which let you repeat steps without copying them again and again. For now, it is great that they can spot the pattern!

The Big Idea: Order Matters in Code

Everything you have learned in this module comes together here:

Decomposition: You broke the story, the square, and the animation into small steps
Sequencing: You put the blocks in the right order -- top to bottom
Clear instructions: Each Scratch block does exactly one thing, like each step in your instructions
Flowcharts: A Scratch block stack is like a flowchart -- it shows steps connected in order

When you snap blocks together in Scratch, you are writing code. And writing code is just writing very clear, very specific, step-by-step instructions. You already know how to do that!

Bonus Challenge: Create Your Own Story

Your Challenge

Make the Scratch cat (or a different sprite) tell a 4-line joke or short story. Here is a plan:

Think of something for the sprite to say (a joke, a fun fact, or a little story).
Break it into 4 lines.
Use "say for 2 seconds" blocks for each line, snapped together in order.
Add a "move" or "switch costume" block somewhere to make it more interesting.
Click the green flag and watch!

There is no wrong answer here. The point is to practice putting blocks in order to make something fun happen.

Check Your Understanding

1. In Scratch, which block does the computer run first?

Answer: The computer runs the block at the top of the stack first, then moves down to the next block, and so on. It reads from top to bottom, just like we read a list.

2. What does the "pen down" block do?

Answer: "Pen down" makes the sprite leave a trail (draw a line) as it moves. It is like putting a marker on paper. "Pen up" makes it stop drawing.

3. How is a stack of Scratch blocks like a recipe?

Answer: Both are a set of steps in a specific order. A recipe tells you to do things one step at a time from top to bottom. A Scratch stack does the same thing -- each block is one step, and they run in order from the top block to the bottom block.

Key Takeaways

Scratch runs blocks from top to bottom, one at a time, just like reading a list
You can make a sprite tell a story using "say" and "wait" blocks in sequence
You can make a sprite draw shapes using "move" and "turn" blocks with the pen
Changing the order of blocks changes what happens, just like reordering recipe steps
A stack of Scratch blocks is really just a set of clear, ordered instructions -- and you already know how to write those!

What is Next?

Practice Activities

Try more decomposition challenges, instruction-writing tasks, and Scratch sequencing activities.

Practice Activities

Module Quiz

Ready to test what you know? Take the Module 3 quiz!

Take the Quiz

Module 4

In Module 4, you will learn about making decisions -- if/then thinking, yes/no questions, and decision trees!

Go to Module 4