Session 3 — Costumes, Looks & Sound

Duration: 60 min · Format: live online

Session goal: by the end, students can make a sprite talk, change size and colour, animate by flipping between costumes, and play a sound — using the purple Looks blocks and the pink Sound blocks.

Soft skill focus — Creativity

Today's human skill: Creativity. Costumes, colours, size and sound are the paint box for bringing a character to life — no two students' sprites have to look or sound the same.

• Build it in class: during "bring your sprite to life," resist showing one "right" answer. Invite students to give their sprite a personality — its own words to say, its own colour, its own sound — and celebrate the weird and wonderful ones out loud ("I love that yours whispers and shrinks!").
• Reflection (wrap-up): ask "What did you do to make your sprite different from everyone else's?"

Before class — prep

• Open Scratch in a tab (signed in if you can, so you can save) and be ready to screen-share the editor.
• Have the story scenes / costumes diagram below open to share.
• Pick a sprite with two costumes ahead of time (the cat has costume1 and costume2) and open the Costumes tab so you can show it fast.
• If any student can't run Scratch, have the low-tech fallback (flip-book costumes) ready — see Teaching notes.

Hook

Do a quick "flip-book" trick. On a sticky note or two drawings, show a stick figure with arms down, then arms up. Flip between them fast: "Look — it's waving! But it's just two pictures swapped quickly."

Then reveal: "That's exactly how cartoons and games work — and how your sprite will walk today. You'll also make it talk, grow, shrink, change colour and play a sound. Let's open the purple Looks blocks."

Teach — Looks blocks: say, size & colour

Share this diagram and point out that swapping costumes is what makes a sprite look alive:

Explain: the Looks blocks are all purple — they change how a sprite looks and what it says. Build these live on your shared screen.

Build this together:

1. From Events (yellow), drag when green flag clicked.

2. From Looks (purple), snap say [Hello!] for 2 seconds. Press the flag — a speech bubble pops up. Swap it for think [Hmm…] for 2 seconds and run again — now it's a thought bubble.

3. Add change size by 10 and run a few times — the sprite grows. Then try change size by -10 to shrink it. Show set size to 100 % to snap it back to normal.

4. Add change color effect by 25 and press the flag several times — the sprite cycles through colours. Show clear graphic effects to reset it.

when green flag clicked
say "Hello!" for 2 seconds
change size by 20
change color effect by 25

Show show and hide. From Looks, hide makes the sprite vanish; show brings it back. Great for making a character appear or disappear in a story.

⚠ Watch for the invisible sprite: if a student's sprite disappears and won't come back, they probably ran a hide (or set size to a tiny number). Fix it with a show block and set size to 100 %. A sprite you can't see is usually hidden, not deleted.

Ask: "Which block makes a thought bubble instead of a speech bubble?" (Answer: think.)

Teach — Costumes = animation + Sound blocks

The big idea: switching costumes quickly = animation. Open the Costumes tab (top-left) and show that the cat has two costumes — costume1 and costume2 — with the legs in different positions.

Build this together:

1. Start with when green flag clicked.

2. From Looks, add next costume inside a repeat so it flips back and forth. Add a tiny wait so we can see it:

when green flag clicked
forever
next costume
wait 0.2 seconds

Press the flag — the cat's legs move: it's walking on the spot! Explain: next costume just flips to the next picture; doing it fast, over and over, is animation. (Don't worry about forever — that's Session 4; it means "keep doing this.")

3. Show switch costume to [costume1] — this jumps to one exact costume by name, instead of just the next one. Useful when you want a specific pose.

Now add sound. Open the Sound palette — these blocks are pink. Build:

1. From Sound, add play sound Meow until done — the program waits for the whole sound to finish before moving on.

2. Compare with start sound Meow — this starts the sound and keeps going straight away (no waiting).

3. Show change volume by -10 and set volume to 100 % to make sounds quieter or louder.

Explain the key difference: play sound … until done waits for the sound; start sound … doesn't wait and lets the next block run right away.

Ask: "You want the cat to meow and keep walking at the same time — which sound block?" (Answer: start sound — it doesn't wait.)

Activity — Bring your sprite to life

Students make a sprite talk, animate and make a sound. Demo the first step, then let them go and circulate.

1. Open a new project at Scratch.
2. Talk: build when green flag clicked → say "Hi, I'm [name]!" for 2 seconds → think "What should I do?" for 2 seconds.
3. Animate: add forever → next costume → wait 0.2 seconds so the sprite looks like it's moving. Try different wait numbers — faster or slower.
4. Change looks: add change size by 20 and change color effect by 25. Run it a few times.
5. Add sound: from the Sound palette, add start sound Meow (or choose another sound from the sound library).
6. Make it yours: change the words, the costume speed, the size and the colour until your sprite feels alive.

Circulate and ask: "Show me the block that makes it walk. What's the difference between your say and your think?"

Debrief: ask 2–3 students to share their screen and run their sprite for the class.

Check for understanding

Ask these aloud or in the chat. Answer key (for you):

1. What makes a sprite look animated — like it's walking? → Switching costumes quickly (e.g. next costume over and over). Fast picture-swapping = animation.
2. What's the difference between say and think? → say makes a speech bubble; think makes a thought bubble. Both show your words above the sprite.
3. What's the difference between play sound … until done and start sound …? → play sound … until done waits for the sound to finish before the next block runs; start sound … doesn't wait — the next block runs right away.

Wrap-up + homework

• Ask one student to explain, in one sentence, why switching costumes quickly makes a sprite look alive.
• Homework — Make it alive: make your sprite say something, switch costumes to walk, and play a sound, then press the green flag. Screenshot it for your portfolio.

Teaching notes

• Correct this misconception: "next costume moves the sprite." No — it only changes the picture, not the position. The sprite looks like it's walking but stays in one spot unless you also add a Motion block (move/glide). Animation (Looks) and movement (Motion) are two different jobs; real walking uses both together.
• Fast finishers (extension): have them combine this session with Session 2 — a sprite that moves across the stage and switches costumes so it actually walks: forever → move 10 steps → next costume → wait 0.1 seconds → if on edge, bounce. Ask them to add a say that changes with a second costume.
• Low-tech fallback: no devices? Make a two-frame flip-book. Each student draws a character twice on two cards — same character, slightly different pose (arms up / arms down). Flip between them fast and watch it "move." Then discuss: adding a third and fourth pose makes it smoother. That is costume animation.

Vocabulary

Resources

• Scratch editor — where students build (free, in the browser).
• Scratch Ideas page — official tutorials, including "Animate a Character" and "Make Music".
• Scratch Starter Guide (PDF) — a one-page getting-started sheet.

Practice set

Extra tasks to explore Looks and Sound. Work them easy → hard, at lab time or for homework. Answers follow each arrow.

1. Colour clue. You want your sprite to grow. Which palette and colour do you look for? → Looks — purple.

2. Bubble type. Which block gives a thought bubble: say or think? → think.

3. Grow or shrink. Which makes the sprite smaller: change size by 20 or change size by -20? → change size by -20 — a negative number shrinks it.

4. Predict. The script is when green flag clicked → forever → next costume → wait 0.2 seconds. What does the sprite look like? → It looks animated — it flips between costumes, like walking or wiggling on the spot.

5. Make it (build task). Build a script so the sprite says "Watch me!", then plays a sound, then changes colour. → when green flag clicked → say "Watch me!" for 2 seconds → start sound Meow → change color effect by 25.

6. Fix it (harder). A student's sprite has vanished and won't come back, even after pressing the green flag. What two blocks bring it back? → show (it was hidden) and set size to 100 % (in case it was shrunk to nothing).

Going deeper (optional)

Optional — for a class that's animating a sprite and wants to know how real animation works.

Frames per second. Cartoons and games flash many pictures every second — often 24 or more — and your eye blends them into smooth motion. In Scratch, each costume is one frame, and the wait block controls the speed: a smaller wait means more flips per second and smoother movement. Have students experiment with wait 0.05 vs wait 0.5 and describe the difference.

Effects are temporary tricks. change color effect and change size don't repaint the costume — they put a filter over it, like sunglasses. That's why clear graphic effects and set size to 100 % snap everything back instantly. Understanding that effects sit on top of the real costume helps students reset a project that's gone weird.

Common mistakes & fixes

• Mistake: Expecting next costume to move the sprite across the stage. → Fix: it only changes the picture; add a Motion block (move/glide) for real movement.
• Mistake: The sprite disappears and won't come back. → Fix: it was probably hide-den or shrunk — add show and set size to 100 %.
• Mistake: Costumes flip so fast you can't see them (no wait). → Fix: add a wait 0.2 seconds between switches to slow the animation down.
• Mistake: A sound "won't play." → Fix: check it was added from the Sound tab first, and that the volume isn't set to 0; try play sound … until done.
• Mistake: The next block runs before a sound finishes and cuts it off. → Fix: use play sound … until done when you need the whole sound before moving on.

Next session

Session 4 — Events & Loops: students learn the two ideas every program needs — an event that starts code (green flag, key press, sprite click) and a loop that repeats it (forever, repeat 10). Together they make the "game loop" that powers every game.