Year 8 Science: Density

Science lesson presentation with a hook, a worked example and an exit ticket

This is a 50 minute Year 8 lesson on density built the way an explicit teaching lesson runs: a hook, the intentions, the terms, a model, a worked example, practice with real data, two checks and an exit ticket. The slide order is the lesson plan, so a teacher can swap density for any topic and keep the structure.

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YEAR 8

SCIENCE · LESSON 4 OF 6 · 50 MINUTES

Density:

Why Ships Float

The lesson where heavy things float and light things sink.

Ms Arden

Year 8 Science, Room 12

HOOK · MODEL · PRACTICE

Slide 1 · cover · A playful cover that still names the unit, the lesson number and the time.

The hook

A ship made of 3,000 tonnes of steel floats. A 3 gram grain of sand sinks. By the end of this lesson you can explain why in one sentence.

THINK ABOUT IT

Floats

Steel ships, ice cubes and cooking oil all float on water.

Sinks

Sand grains, iron nails and marbles all sink in water.

The rule

It is not about heavy or light. It is about something else.

02

Slide 2 · intro · The hook is a contradiction, and the exit ticket will ask it again at the end.

LEARNING INTENTIONS

What today is for

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

State the density formula and the units it is measured in.

Calculate density from mass and volume for a solid or liquid.

Measure the volume of an irregular object by displacement.

Predict whether a material floats or sinks from its density.

Complete the data table and check answers against the class chart.

Explain the ship and the sand grain using the particle model.

03

Slide 3 · content · Learning intentions and success criteria, so students can judge their own exit ticket.

Key terms

Six terms the worksheet uses. Say them out loud once each.

Mass

How much matter an object contains, measured in grams or kilograms. Not the same as weight.

Volume

How much space an object takes up, measured in cm³ or mL. One cm³ equals one mL.

Density

Mass packed into each unit of space. The property that decides floating and sinking.

The formula

Density = mass ÷ volume, giving grams per cm³. Rearrange it to find any missing value.

Displacement

Measuring volume by the water an object pushes aside when submerged.

Buoyancy

The upward push of a fluid. It wins when the object is less dense than the fluid.

04

Slide 4 · content · The vocabulary settled before the practice, formula included as a term.

Why density differs

Start at the core: the same idea explains every material on the worksheet.

Particles
Arrangement
Density
Float or sink

FROM THE CORE OUT

1
PARTICLES

Every material is made of particles with their own mass.

2
ARRANGEMENT

How tightly those particles pack differs by material.

3
DENSITY

Tight packing of heavy particles means high density.

4
FLOAT OR SINK

Less dense than water floats; denser than water sinks.

05

Slide 5 · diagram · The particle model in four rings: particles at the core explain the floating at the surface.

Worked example

A metal block from the tray. Follow on the board, then the table is yours.

01

Measure mass

The block reads 54 g on the balance. Write it down with the unit.

02

Measure volume

Water rises from 80 mL to 100 mL when the block goes in: volume 20 cm³.

03

Divide

Density = 54 ÷ 20 = 2.7 g/cm³.

04

Compare

2.7 g/cm³ matches aluminium on the reference chart, and it is denser than water, so it sinks.

06

Slide 6 · process · The worked example, done slowly on the board while this stays up as the map.

YOUR TURN

Fill the last column

Material
Mass (g)
Volume (cm³)
Density (g/cm³)
Cork
12
50
?
Ice
92
100
?
Water
100
100
?
Cooking oil
46
50
?
Iron
236
30
?
Class results from the practical, rounded to one decimal place.

07

Slide 7 · metrics · The activity table with the density column left as question marks: that column is the lesson.

Answers

Anything under 1.0 g/cm³ floats in water. Check your column against the bars.

Cork
Ice
Cooking oil
Water
Iron
02468
Density (g/cm³)

08

Slide 8 · metrics · The answers revealed as bars, with the float line at 1.0 stated in the description.

CHECK 1

Which of these will float in water?

1

An oak block, density 0.7 g/cm³

2

A steel bolt, density 7.8 g/cm³

3

A glass marble, density 2.5 g/cm³

4

A copper coin, density 8.9 g/cm³

Answer: A. Anything with density under 1.0 g/cm³ floats in water.

09

Slide 9 · quiz · Check one tests the prediction intention with four densities to choose from.

CHECK 2

Ice is less dense than liquid water, which is why ice cubes float in your drink.

True

False

True. Water expands as it freezes, so ice is about 8% less dense than the water around it.

10

Slide 10 · quiz · Check two tests the ice anomaly, the fact students argue about most.

Exit ticket

Explain the ship and the sand grain in one sentence, on paper.

Calculate: a 138 g stone displaces 60 mL. Density? Float or sink?

Predict: honey is 1.4 g/cm³. What happens to an ice cube in honey?

Papers in the tray by the door before the bell.

Next lesson: buoyancy, and why submarines get to choose.

11

Slide 11 · takeaway · The exit ticket asks the hook again, which is how the lesson proves it taught something.

The structure

What each slide is doing, so you can reuse the order even with different content.

Slide 1cover
A playful cover that still names the unit, the lesson number and the time.
Slide 2intro
The hook is a contradiction, and the exit ticket will ask it again at the end.
Slide 3content
Learning intentions and success criteria, so students can judge their own exit ticket.
Slide 4content
The vocabulary settled before the practice, formula included as a term.
Slide 5diagram
The particle model in four rings: particles at the core explain the floating at the surface.
Slide 6process
The worked example, done slowly on the board while this stays up as the map.
Slide 7metrics
The activity table with the density column left as question marks: that column is the lesson.
Slide 8metrics
The answers revealed as bars, with the float line at 1.0 stated in the description.
Slide 9quiz
Check one tests the prediction intention with four densities to choose from.
Slide 10quiz
Check two tests the ice anomaly, the fact students argue about most.
Slide 11takeaway
The exit ticket asks the hook again, which is how the lesson proves it taught something.

How to adapt this deck

A humanities lesson keeps every beat and swaps the data table for a source analysis grid; the blank column becomes the inference column and the reveal becomes a modelled reading. A double period runs the same deck with a second practice cycle inserted after the first check, not a longer lecture at the front. For primary school, cut the key terms to three, make the hook physical, a bucket and five objects beats any slide, and keep the exit ticket to one question. Grade 8 readers outside Australia can read Year 8 as the same age band. Across every version the check slide is the one that cannot be cut. A lesson without a mid point check is a lecture with slides, and the whole point of the reveal and practice cycle is that the teacher finds out who is lost while there is still time in the period to do something about it.

What makes this deck work

The hook is a contradiction the exit ticket answers

Slide two asks why 3,000 tonnes of steel floats while 3 grams of sand sinks, and slide eleven makes explaining it the first exit ticket question. Opening and closing on the same puzzle gives the lesson a visible arc, and gives the teacher a clean read on who actually got there.

The table leaves the answer column blank

Slide seven lists cork, ice, water, oil and iron with mass and volume filled and density as question marks, and the next slide reveals the answers as bars with the float line named at 1.0. The blank column is the practice; the reveal chart is the feedback, thirty seconds later.

Two checks map to the two intentions

The multiple choice tests prediction from density, with four options and the answer in the hint line, and the true or false tests the ice anomaly. One check per learning intention, placed after practice, is the explicit teaching pattern, and the deck makes it visible enough to reuse for any topic.

Questions people ask

How do I structure a lesson presentation?

Hook, intentions, vocabulary, model, worked example, practice, check, exit ticket. That is the slide order here, and it mirrors the explicit teaching sequence: show, do together, do alone, check. Swap the density content for any topic and the eleven slide skeleton holds.

How many slides for a 50 minute lesson?

Ten to twelve, because the middle of the lesson is students working, not watching. This deck holds two slides, the data table and the answers, on screen for almost twenty minutes of activity. More slides than that usually means the deck is doing the talking the teacher should be.

Should the answers be in the deck?

Yes, on their own slide after the practice, the way the density bars follow the blank table. Instant feedback beats marking the sheet overnight. The quiz layouts keep their answers in a hint line the class cannot see, so the reveal stays under the teacher’s control.

How do I use the quiz slides in class?

Put the question up, take hands or mini whiteboards, then reveal. The multiple choice slide holds four options in a grid and the true or false slide holds one statement, and both carry the answer as presenter facing hint text, so the room commits before the reveal.

Can students open the deck on their phones?

Yes. A share link opens read only on mobile and always shows the latest saved version, so absent students see exactly the lesson that ran. The speaker notes pane does not exist below 1024 pixels, so notes stay private from a phone audience by construction.

Can I export the lesson for the school’s PowerPoint?

Yes. The editable PPTX export keeps the data table as a native table and the bar chart as a native chart on paid plans, so a colleague can change the materials or the numbers in PowerPoint. The free PDF export prints one clean page per slide for handouts.

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