These 30 science riddles for kids cover states of matter and magnets, space and weather, and the human body and plants. Every riddle has two hints, a hidden answer and a one-line explanation of the science behind it. They suit ages 7 to 12, and you can print them as cards for a science lesson or a quiet moment at home.
Ice, water vapor, air and magnets: riddles about how everyday materials behave.
I am hard and cold, and I am really water. Leave me out in the sun and I turn into a puddle. What am I?
I am the solid form of water.
I float in your drink and melt when it gets warm.
Ice
Why it works: Ice is frozen water, and warmth makes it melt back into liquid.
Did you guess it?
I am all around you. I have no color or taste, and you need me to breathe. What am I?
You cannot see me, but you can feel me when the wind blows.
I fill up a balloon when you blow in.
Air
Why it works: Air is the invisible mixture of gases around us, and it contains the oxygen we breathe.
Did you guess it?
I can pull a paper clip toward me without touching it. I have a north end and a south end. What am I?
I stick to the fridge.
My two ends are called poles.
A magnet
Why it works: Magnets pull on iron and steel objects, and every magnet has a north and a south pole.
Did you guess it?
I am the force that makes your hands warm when you rub them together. I also slow down a sled sliding on the snow. What am I?
I happen whenever two surfaces rub against each other.
I am why shoes with a rough bottom do not slip.
Friction
Why it works: Rubbing surfaces push against each other, which slows movement and turns some of it into heat.
Did you guess it?
I am a bottle with two walls and empty space in between. I keep hot soup hot and cold juice cold. What am I?
You might take me on a picnic or to school.
The empty gap slows heat moving between the inner and outer walls.
A thermos
Why it works: The gap between the walls slows heat moving through, so the drink keeps its temperature.
Did you guess it?
Two magnets sit with their north ends facing each other. What do they do to each other?
Think about what happens when you try to push two like ends together.
Like poles do the opposite of attract.
They push apart
Why it works: Matching poles push apart, while opposite poles pull together.
Did you guess it?
I am water, but you cannot see me. I rise up from a pot of boiling water as a gas. What am I?
I am the gas form of water.
Heat turns water into me.
Water vapor
Why it works: Boiling turns liquid water into an invisible gas called water vapor.
Did you guess it?
What do you call it when sugar stirred into hot tea seems to vanish but you can still taste it?
The sugar breaks into pieces too small to see.
It mixes completely into the liquid.
Dissolving
Why it works: The sugar spreads out as tiny particles through the tea, so you cannot see it but it is still there.
Did you guess it?
I am the reason a puddle disappears on a sunny day, but the water is not gone. It has become a gas. What am I?
Heat from the sun gives water the energy to change.
The liquid water turns into an invisible gas in the air.
Evaporation
Why it works: Sunlight warms the puddle, so its water turns into water vapor faster and rises into the air.
Did you guess it?
I make little water drops appear on the outside of a cold glass on a warm day. What am I?
The drops do not leak from inside the glass.
Water vapor in the air touches something cold.
Condensation
Why it works: Water vapor in the air cools on the cold glass and turns back into liquid drops.
Did you guess it?
The Sun, planets, clouds, storms, volcanoes and the water cycle.
I am a star, and I am the closest one to Earth. I give you light and heat every day. What am I?
You see me in the sky in the daytime.
Earth travels around me once a year.
The Sun
Why it works: The Sun is the star at the center of our solar system and our main source of light and heat.
Did you guess it?
I am a rusty red planet, the fourth from the Sun. Robots with wheels have driven across my dusty surface. What planet am I?
My red color comes from iron rust in my dust.
I am next to Earth, a little farther from the Sun.
Mars
Why it works: Mars looks red because its dust contains rusty iron, and robot rovers have explored it.
Did you guess it?
I hold water drops and tiny bits of ice high in the sky. I can be white and fluffy or dark and gray. What am I?
You look up to see me, and I can bring rain.
Planes fly through me.
A cloud
Why it works: Clouds are made of tiny water droplets and ice crystals floating in the air.
Did you guess it?
I appear when sunshine shines through raindrops. I have many colors in a curved band. What am I?
You usually see me when the sun is out just after a shower.
Red is on the outside of my curve.
A rainbow
Why it works: Raindrops bend and split sunlight into its colors, which makes a curved band of color.
Did you guess it?
I am a mountain with a hole at the top. Hot melted rock can burst out of me. What am I?
I can be quiet for hundreds of years, then erupt.
The melted rock that flows from me is called lava.
A volcano
Why it works: A volcano is an opening in the Earth where hot melted rock called lava can escape.
Did you guess it?
What does the Earth do once every 24 hours that gives us day and night?
The Sun does not need to travel around our planet.
Your part of Earth faces the Sun, then turns away from it.
It spins
Why it works: Earth spins on its axis, so each place faces the Sun for part of the day and away for the rest.
Did you guess it?
I am a planet with big, bright rings made of ice and rock. You can see them with a small telescope. What planet am I?
I am the sixth planet from the Sun.
I am a gas giant famous for my rings.
Saturn
Why it works: Saturn has the biggest and most spectacular rings of any planet, made of chunks of ice and rock.
Did you guess it?
Mercury is closer to the Sun than I am, but I am the hottest planet. A thick blanket of gas traps heat on me. What planet am I?
I am the second planet from the Sun.
My dense atmosphere is mostly carbon dioxide, a gas that traps heat.
Venus
Why it works: Venus is hotter than Mercury because its thick atmosphere traps heat from the Sun.
Did you guess it?
We start at the same moment, but you always see me first and hear my partner later. What am I?
I come with a storm.
My partner is the loud rumble.
Lightning
Why it works: Light travels much faster than sound, so you see the flash before you hear the thunder.
Did you guess it?
Rain falls, rivers flow to the sea, the Sun warms the water, and it rises to make new clouds. What is this never-ending trip called?
It goes round and round, like a circle.
The same water is used over and over, in different forms.
The water cycle
Why it works: Water moves between the sea, the air and the land in a loop called the water cycle.
Did you guess it?
How hearts, lungs, seeds and leaves do their jobs.
I am about the size of your fist, and I never take a day off. I pump blood all around your body. What am I?
You can feel me beat if you put your hand on your chest.
I beat faster when you run.
A heart
Why it works: The heart is a muscle that pumps blood around the body, and you can feel it beat.
Did you guess it?
We are a pair inside your chest. You fill us with air each time you breathe in. What are we?
We are protected by your ribs.
We take oxygen from the air and give it to your blood.
Lungs
Why it works: Lungs fill with air when you breathe in and pass oxygen into your blood.
Did you guess it?
I sit inside your head and control your thoughts, your movements and your memories. What am I?
I am protected by your skull.
I send messages to the rest of your body along nerves.
The brain
Why it works: The brain controls thinking and movement by sending messages through the nerves.
Did you guess it?
I am hard, I am inside you, and I hold you up. Without me you could not stand. What am I?
I am a firm framework beneath your muscles.
My parts join at places such as your knees and elbows.
Your skeleton
Why it works: The skeleton is the frame of bones that supports your body and protects what is inside.
Did you guess it?
Plant me in soil and water me, and I grow into a new plant. Inside my hard coat is a tiny baby plant. What am I?
Beans and sunflowers start as me.
I am small, and I need water to wake up.
A seed
Why it works: A seed holds a baby plant and food, ready to start growing when it gets water.
Did you guess it?
I am the part of a plant that grows under the ground. I hold the plant in place and drink up water. What am I?
You cannot see me unless you dig up the plant.
I look like thin threads spreading through the soil.
The roots
Why it works: Roots anchor a plant in the soil and take in water and minerals.
Did you guess it?
I am the biggest organ on the outside of your body. I cover you from head to toe. What am I?
I keep germs out and sense temperature and touch.
I can have freckles and tiny hairs.
Skin
Why it works: Skin covers the whole body, protects it and lets you feel things.
Did you guess it?
I carry yellow dust from flower to flower, and I make honey. What am I?
I buzz around gardens.
My yellow dust helps flowers make seeds.
A bee
Why it works: Bees carry pollen between flowers, which helps plants make seeds, and honeybees also make honey.
Did you guess it?
I am the tiny unit that makes up living things. Your body contains trillions of me. What am I?
Most of us need a microscope to be seen clearly.
Many of us work together to form tissues and organs.
A cell
Why it works: Cells are the basic units of living things, and the human body contains trillions of them.
Did you guess it?
Plants use sunlight, water and air to make their own food. What is this process called?
It happens mainly in green leaves.
The first part of the word means light.
Photosynthesis
Why it works: In photosynthesis, leaves use light energy to turn water and carbon dioxide into food.
Did you guess it?
No riddles match both filters. Try another age or difficulty.
Read the 'why it works' line aloud after each answer. It is the short science lesson that goes with the riddle.
Pair a riddle with a quick demo: two bar magnets for repel, a cold glass of water for condensation, or a bowl of ice left in the sun.
Use a topic group as a starter for a unit. Try the space riddles before a planets lesson, or the plant riddles before growing seeds.
For ages 7 to 9, read the riddle and give hint one straight away. For ages 10 to 12, hold the hints back and let them argue it out.
Ask children to write one riddle of their own about a science word they learned this week.
They are written for ages 7 to 12. The earlier riddles in each group use everyday words and familiar objects. The later ones use science vocabulary such as evaporation, condensation and photosynthesis.
Yes. Each answer is kept to what is correct at a primary school level, and the one-line explanation says why the clues point to that answer. If a child gives a different answer that fits every clue, count it as right.
Yes. Use one as a starter or exit question, or print the cards and run a team quiz. The explanation lines make quick revision of states of matter, the solar system and body systems.
Split the class into teams, read a riddle, and give each team a minute to agree an answer on a whiteboard. Give a bonus point for a team that explains the science without the hints.
Yes. Use the print option to get riddle cards plus a separate answer key, so children can answer without seeing the solutions.