Jupiter2U School
Chapter 02

Hot & Cold, Light & Shadow

Kindergarten
At a glance
Core ideaHeat always flows from hot to cold, and light travels in straight lines.
Key termShadow — the dark shape left where an object blocks the light.
You can…Explain why an ice cube melts in your warm hand.
Watch outCold never "moves" — only heat does; the Moon makes no light of its own.
Theory

Hot, cold, and how light makes shadows

Touch a cup of warm milk — it feels hot. Touch an ice cube — it feels cold. Heat always moves from hot things to cold things, never the other way. That's why an ice cube melts in your warm hand, and why hot soup slowly cools down on the table.

Light travels in straight lines. When something blocks the light — like your hand, or a tree — it makes a dark shape behind it called a shadow. No light can get past the object, so the ground behind it stays dark.

Where does light come from?

The Sun, a lamp, and a flashlight all make their own light. The Moon does not — it only looks bright because it reflects the Sun's light, like a mirror.

Explanation

Why your shadow changes shape

Stand outside in the morning and your shadow is long. Stand at lunchtime and it's short. That's because the Sun is low in the sky in the morning (so light comes in at a slant, casting a long shadow) and high overhead at noon (so the shadow shrinks underneath you).

Ice melts because your hand is warmer than the ice. Heat flows out of your warm hand into the cold ice until the ice turns to water. The ice isn't "sucking out the cold" — cold doesn't move, only heat does, from hot to cold.

Try noticing. On a cloudy day, shadows almost disappear — clouds spread the sunlight out in every direction instead of letting it travel in one straight beam.
Practical

Try it — shadow puppets and warm-or-cold sort

  1. In a dark room, shine a flashlight at a wall. Hold your hand between the flashlight and the wall.
  2. Move your hand closer to the flashlight — watch the shadow get bigger. Move it away — watch the shadow shrink.
  3. Make a shape with your fingers (like a "bird") and see its shadow on the wall.
  4. Now collect a few safe household objects (a spoon from the fridge, a cup of warm water, a pillow, an ice cube). Touch each one and sort them into "hot," "cold," and "neither."
Q&A
Does the Moon make its own light?

No! The Moon reflects light from the Sun, like a big mirror in the sky.

Why does an ice cube melt in your hand?

Your hand is warmer than the ice, so heat flows from your hand into the ice until it melts.

What happens to a shadow if you move closer to the flashlight?

It gets bigger! Being closer to the light makes shadows stretch larger.

Can light bend around a corner to make no shadow?

No — light travels in straight lines, so if something blocks its path, a shadow forms. Light can't sneak around corners on its own.

Concept mind map

How the ideas connect

Every key idea in this chapter, branching from the core concept — use it to see the whole picture at a glance.

Hot thingsCold thingsLight travelsShadows formBlocking lightSun positionHot & Cold, Light & Shadow
Infographic

The key facts, visualised

Hot
Feels warm, like the Sun or soup
Cold
Feels chilly, like ice or snow
Light
Comes from the Sun, lamps and fire
Shadow
A dark shape where light is blocked
Solved examples

Worked problems, step by step

Follow each solution line by line, then try to reproduce it on paper before moving on.

Example 1Why does your body make a shadow on a sunny day?

  1. The Sun shines light at you
  2. Your body blocks some light
  3. The blocked spot stays dark

Example 2Ice cream and hot cocoa: which is hot, which is cold?

  1. Ice cream feels chilly
  2. Cocoa feels warm
Practice problem set

Now you try

Work each one out first, then tap to reveal the worked answer.

1Is a snowball hot or cold?
A snowball is cold because it is made of frozen water.
2What do you need to make a shadow?
You need light and something to block it.
3Why is your shadow long in the early morning?
The Sun is low, so it casts a long shadow.
4Name two things that give off light.
The Sun and a lamp both give off light.
5Is a cup of tea from the kettle hot or cold?
It is hot because the kettle warmed the water.
6Can you see your shadow in a dark room with no light?
No, you need light to make a shadow.