Phases of the Moon: Why It Looks Different Every Night

Objective. Students will name the eight phases of the Moon in order, explain that the changing appearance is caused by which side is lit by the Sun, and distinguish 'waxing' (illuminated portion increasing) from 'waning' (illuminated portion decreasing).

Overview

Most fifth graders have noticed the Moon changes shape but assume the Moon itself is changing — clouds in front, or the Moon shrinking and growing. This lesson untangles that misconception by anchoring the appearance change to a single fact: the Moon is always half-lit by the Sun, and we see different fractions of the lit half depending on where the Moon is in its orbit. Students model phases with a styrofoam ball and a flashlight, name them in order, and use the words waxing and waning correctly by exit ticket.

Materials

Styrofoam ball on a stick (one per student) (28) scaffolded
Flashlight (one per pair, bright enough to cast a clear shadow) (14) scaffolded
Phase-of-the-Moon order strip (printed, blank for student labeling) (28) scaffolded
Anchor poster of the eight phases (printed, large) (1) scaffolded
Exit ticket: 4 unlabeled phase images (28) scaffolded

Demonstration

One bright flashlight at the front of the room (the Sun) and a student holding a styrofoam ball at arm's length. The student slowly rotates in place while keeping the ball pointed at the flashlight. From the student's perspective, the lit fraction of the ball matches the eight phases in order. AI-generated — review

Materials: bright flashlight, styrofoam ball on a stick, darkened room

Teacher tip: Dimming classroom lights makes the lit/unlit boundary on the ball much sharper. If you have a black backdrop, set the demo up against it for contrast.

Lesson Steps

(5 min) Teacher: Show a time-lapse of the Moon over a month. Ask: 'What is changing — the Moon, or the way we see it?' Take 3-4 student answers without correcting yet.
Students: Watch the time-lapse. Share predictions about what is causing the Moon to look different each night. AI-generated — review
(10 min) Teacher: Teach the core idea: the Moon is always half-lit by the Sun. We see different fractions of that lit half because the Moon orbits Earth. Demonstrate with a flashlight and a ball at the front of the room.
Students: Watch the demonstration. Answer the check question: 'Is the Moon ever fully dark on its own?' (Answer: only the side facing away from the Sun.) AI-generated — review
(18 min) Teacher: Pair students. Give each pair a flashlight and ball-on-stick. Walk them through the eight phases in order, pausing at each so they can see the lit fraction change. Introduce 'waxing' and 'waning' at first quarter and third quarter respectively.
Students: Model each phase with the ball and flashlight. Label the phase strip in order. Discuss with partner whether the Moon is currently waxing or waning. AI-generated — review
(7 min) Teacher: Distribute the exit ticket: four unlabeled phase images. Students name each and mark waxing or waning. Collect.
Students: Complete the exit ticket independently. AI-generated — review
(5 min) Teacher: Quick share-out: ask which phase is happening tonight (look it up live). Send students out with the homework: observe and sketch the Moon for three nights this week.
Students: Note tonight's expected phase. Take home the observation log. AI-generated — review

Assessment (exit ticket, 7 min)

Q1. Name the phase between New Moon and First Quarter. scaffolded
Expected: Waxing crescent.
Rubric: Full credit for 'waxing crescent.' Half credit for 'crescent' alone.
Q2. True or false: a waxing Moon means the lit part we see is getting smaller each night. scaffolded
Expected: False — that describes waning.
Rubric: Award full credit only if student identifies the statement as describing waning rather than waxing.

Teacher Notes

If you can, time this lesson to the week of a first-quarter or last-quarter Moon — students seeing 'tonight's' phase in the sky after class is the strongest hook back to the content. Some students will conflate phases with eclipses; note in step 2 that an eclipse is rare and different. The high-energy step is the ball-and-flashlight demo (step 3) — pre-set noise expectations and use a simple chime to call students back.

Discussion Prompts

(deepen understanding) Why does the same Moon look different from one week to the next, even though it isn't changing shape? AI-generated — review
(deepen understanding) If you saw a 'C-shaped' Moon last night, would you expect to see a fuller Moon or a thinner Moon next week? How can you tell? AI-generated — review
(extend beyond lesson) Astronauts on the Moon would see Earth go through phases too. What do you think Earth would look like from the Moon during our 'full moon'? AI-generated — review

Vocabulary

phase scaffolded: The shape of the lit part of the Moon as we see it from Earth.
Example: Tonight's phase is a waxing crescent.
waxing scaffolded: When the lit portion of the Moon we can see is getting bigger night after night.
Example: The Moon is waxing on its way from new to full.
waning scaffolded: When the lit portion of the Moon we can see is getting smaller night after night.
Example: After full moon, the Moon is waning.
new moon scaffolded: The phase where the side of the Moon facing Earth is entirely in shadow.
full moon scaffolded: The phase where the side of the Moon facing Earth is fully lit by the Sun.

Common Misconceptions

Misconception: The Moon changes shape, getting bigger and smaller each month.
Correction: The Moon's shape is constant — only the part lit by the Sun and visible from Earth changes.
How to address: Use the ball-and-flashlight demo. Walk a student around the room and ask: 'Is the ball changing shape, or is your view of the lit side changing?'
Misconception: Clouds or Earth's shadow cause the phases.
Correction: Phases are caused by the Moon's orbit around Earth, which changes the angle from which we see the Moon's lit half. Earth's shadow causes a lunar eclipse, which is rare and different from the regular monthly cycle.
How to address: Show a diagram of Earth and Moon with the Sun off-screen. Trace the Moon around its orbit and point out that Earth's shadow only crosses the Moon during eclipses.

Differentiation

Struggling: Pair with a partner who has already grasped the orbit demo. Provide a printed phase-name word bank for the exit ticket. Allow drawing the lit fraction instead of writing the phase name.

Advanced: Ask: 'Why is there roughly 29.5 days between full moons but the Moon's orbit around Earth is 27.3 days?' (Earth has moved in its own orbit; the Moon has to catch up.)

Multilingual: Pre-teach 'phase,' 'waxing,' 'waning,' 'orbit,' and 'illuminate' with cognates and visual labels on the anchor poster.

Accommodations for students with disabilities

Supports for IEP/504 accommodations tied to this lesson. Pair with the student’s existing plan.

Visual: Anchor poster + ball/flashlight demo gives a visual reference at every step. For students with low vision, have them feel the ball during the demo to map lit vs. shadow tactilely (warm side faces the flashlight).
Auditory: Repeat the 'half-lit always' core idea verbally three times: at intro, mid-demo, and exit ticket. Caption the time-lapse video.
Motor / physical: For students who cannot easily walk the orbit, partner them with a peer and have them rotate the ball in their hands while the partner moves the flashlight.
Cognitive / attention: Use the order strip as a visual scaffold for the exit ticket; allow it as a reference if needed.
Behavioral / emotional: Step 3 is the high-energy phase. Pre-set noise expectations and use a simple chime to call students back.