I am a metal, and at room temperature I am a silver liquid. For a long time I was the shining line inside a thermometer. What element am I?
I pull everything toward the center of the Earth. I am why a dropped ball falls, and on the Moon I am only about one sixth as strong. What am I?
I am the flat green part of a plant, and I work like a kitchen. Sunlight lands on me, and I use it to turn water and air into food. What am I?
I cannot be made and I cannot be destroyed. I can only change form, from motion to heat, or from sunlight to electricity. What am I?
I am your largest organ, and you wear me on the outside. I keep germs out and water in. What am I?
I am rock that was once melted. I form when magma or lava cools and hardens, and granite and basalt are two of my kinds. What kind of rock am I?
My name is built from Greek words for small and look. Put a very small thing under me, and it looks big enough to study. What am I?
I am the water in the air that you cannot see. When there is a lot of me, a hot day feels hotter, because the sweat on your skin is slow to dry. What am I?
I begin deep underground at a point called the focus. The place on the surface right above it is my epicenter. What am I?
In one form I am the soft gray tip of a pencil. In another I am a diamond, one of the hardest things known. What element am I?
These science riddles are what-am-I questions from school science: living things, the human body, Earth and weather, matter and energy, tools and inventions. The line under each answer gives the fact in plain words.
Read the full guide
Easy science riddles for kids, and harder ones
Easy answers are words from the early grades: a leaf, a mammal, a lever, a gas. Medium and Hard ask for the words of a later unit, such as chlorophyll, condensation, inertia or metamorphic rock.
STEM riddles: tools and inventions
Tools and inventions is the technology and engineering part: the six simple machines, a circuit, an electromagnet, a robot, a prototype and the engineer who builds one.
After each answer, ask the table for one more fact about it before you go on.
In class, read one riddle as the opening question of the unit it belongs to.
Questions and answers
What is a fun science riddle?
I am a magnet you can turn off. Wind a wire around an iron nail and send a current through the wire, and I wake up. What am I? An electromagnet.
Are there muscle riddles here?
Yes. The human body set has eight: the biceps, the triceps, the heart, the diaphragm, the largest muscle, the longest, the smallest, and why the word muscle means little mouse. One more is about tendons.
What grade are these science riddles for?
Easy suits about grades 2 to 4, Medium grades 4 to 6 and Hard grade 6 and up, as a rough guide. The levels follow no school standard, so read a set through before you use it in class.
A moth spins a cocoon, and a butterfly does not. I am the hard case a caterpillar turns into while its wings form inside. What am I?Answer: A chrysalis. The pupa of a butterfly is called a chrysalis.
A plant cannot walk, so it sends me. I may ride the wind, float down a stream or stick to the fur of an animal going by. What am I?Answer: A seed. Seeds are spread by wind, by water and by animals.
Count my legs and you get six. Count the parts of my body and you get three. An ant is one of me, and a spider is not. What kind of animal am I?Answer: An insect. Insects have six legs and a body in three parts.
I am a chain with no metal in it. My links are grass, a grasshopper, a frog and a hawk, and each link is eaten by the next. What am I?Answer: A food chain. A food chain shows what eats what, starting from a plant.
I am a fine yellow dust made by flowers. Wind and bees carry me from one flower to another, and without me there would be no seeds. What am I?Answer: Pollen. Pollen has to reach another flower before a plant can make seeds.
I am a skeleton worn on the outside. A crab has me, and so does a beetle, and to grow bigger each of them must climb out of me and make a new one. What am I?Answer: An exoskeleton. An exoskeleton cannot grow, so the animal sheds it.
I am nature's cleanup crew. Fungi and bacteria are my best workers: they break down dead leaves and logs and return them to the soil. What am I?Answer: A decomposer. Decomposers break down dead plants and animals.
I am not an animal. I am an animal's address: a pond for a frog, a desert for a lizard, a forest for an owl. What am I?Answer: A habitat. A habitat is the kind of place where a living thing makes its home.
I am the big change in a young animal's life. Because of me a caterpillar ends up with wings and a tadpole ends up with legs. What am I?Answer: Metamorphosis. Metamorphosis is the change of body form that some animals go through as they grow up.
I am the flat green part of a plant, and I work like a kitchen. Sunlight lands on me, and I use it to turn water and air into food. What am I?Answer: A leaf. Most of a plant's food is made in its leaves, by photosynthesis.
I am the green coloring inside a leaf, and my job is to catch sunlight. When I break down in the fall, the yellows that were behind me all summer show through. What am I?Answer: Chlorophyll. Chlorophyll is the green pigment of leaves, and it hides the yellow pigments until it fades.
I am the part of a plant that never sees the sun. I hold the plant in place and drink water from the soil. What am I?Answer: The roots. Roots anchor a plant and take in water.
I belong to a group with eight legs, no wings and no feelers. Spiders are in my group, and so are scorpions and ticks. What kind of animal am I?Answer: An arachnid. Arachnids have eight legs and no antennae or wings.
I eat plants and nothing else. A cow is one of me, and so are a rabbit and a deer. What kind of eater am I?Answer: A herbivore. A herbivore is an animal that feeds on plants.
I grow from the ground, and I am no plant. I have no leaves and no seeds, and I cannot make food from sunlight. Mushrooms and molds are my kind. What am I?Answer: A fungus. Fungi are a kingdom of their own, apart from plants and animals.
My kind has hair or fur, and our mothers feed their babies milk. A whale is one of us, a bat is one of us, and so are you. What kind of animal am I?Answer: A mammal. Mammals have hair or fur and feed their young on milk.
My kind starts life in the water, breathing through gills, and most of us grow up to live on land. Frogs, toads and salamanders are my family. What kind of animal am I?Answer: An amphibian. Amphibians usually begin as larvae in water and move to land as adults.
We are the feathery red parts on each side of a fish's head. Water flows over us, and we take the oxygen out of it. What are we?Answer: Gills. Gills take dissolved oxygen out of water.
You are built of trillions of me. I got my name in the 1660s, when a thin slice of cork under a microscope looked like rows of tiny rooms. What am I?Answer: A cell. The cell was named by Robert Hooke, who saw the walls of dead cells in cork.
The human body 20
Bend your elbow and make a fist, and I bulge on the front of your upper arm. My name means two heads. What muscle am I?Answer: The biceps. The biceps has two heads and bends the elbow.
I am a dome of muscle under your lungs. When I pull down, you breathe in, and when I jump on my own, you hiccup. What am I?Answer: The diaphragm. The diaphragm is the main muscle of breathing, and a hiccup is its sudden twitch.
I am a helmet you were born with. I am made of bone, I have two openings at the front for your eyes, and I guard your brain. What am I?Answer: Your skull. The skull protects the brain.
I am a muscle with four rooms inside me. The two on top take blood in, and the two below push it out again. What am I?Answer: Your heart. The heart is a muscular organ with four chambers: two atria that receive blood and two ventricles that send it out.
I am a stack of 33 small bones running down your back, and a thick cord of nerves is threaded through the middle of me. What am I?Answer: Your spine. The spine, or backbone, is made of 33 vertebrae and shields the spinal cord.
I am a tough cord that ties a muscle to a bone. The thickest one of me is at the back of your heel, and it is named for a hero of Greek myth. What am I?Answer: A tendon. The Achilles tendon is the thickest tendon in the body.
I am the hardest thing in your body, and I am not a bone. I am the white coat on the outside of every tooth. What am I?Answer: Tooth enamel. Enamel is the hardest substance in the human body.
I am the largest muscle in your body, and you are probably sitting on me right now. What muscle am I?Answer: The gluteus maximus. The gluteus maximus is the big muscle of the buttock.
I am the longest bone in your body, and one of the strongest. I run from your hip to your knee. What bone am I?Answer: The femur. The femur, or thigh bone, is the longest bone in the body.
I am the longest muscle in your body, a thin ribbon that crosses the front of your thigh from hip to knee. I am named after tailors, who once sat cross-legged to sew. What muscle am I?Answer: The sartorius. Sartorius comes from the Latin word for a tailor.
I am the place where two bones meet. Your elbow is one of me, your knee is another, and I am the reason you can bend. What am I?Answer: A joint. A joint is the connection between two bones.
I am the smallest muscle you have. I sit inside your ear and steady the smallest bone you have. What muscle am I?Answer: The stapedius. The stapedius is the smallest skeletal muscle, and it steadies the stapes.
I am your largest organ, and you wear me on the outside. I keep germs out and water in. What am I?Answer: Your skin. The skin is the largest organ of the body.
I have about 270 pieces when you are born and 206 when you are grown, because some of my pieces join together. What am I?Answer: Your skeleton. A baby has about 270 bones, and some fuse as the child grows.
I sit inside your skull and run everything. Messages reach me and leave me along the nerves. What am I?Answer: Your brain. The brain is the control center of the nervous system.
I sit on the back of your upper arm. The biceps bends your elbow, and I am the muscle that straightens it again. My name means three heads. What muscle am I?Answer: The triceps. The triceps has three heads and straightens the elbow.
My name comes from the Latin for little mouse, because a flexed one of me was thought to look like the back of a mouse. What part of the body am I?Answer: A muscle. The word muscle comes from the Latin musculus, little mouse.
We are 12 pairs of curved bones, and together we make a cage. Nothing is locked inside us but your heart and your lungs. What are we?Answer: Your ribs. The rib cage has 12 pairs of ribs around the heart and lungs.
We are red and far too small to see, and each of us is shaped like a disc pressed in at the middle. We ride around your body carrying oxygen. What are we?Answer: Red blood cells. Red blood cells carry oxygen from the lungs to the rest of the body.
We are two spongy bags in your chest. We fill with air and empty again all day and all night, even while you sleep. What are we?Answer: Your lungs. The lungs are the organs you breathe with.
Earth and weather 20
I am a ball of iron and nickel at the very center of the Earth. I am about as hot as the surface of the Sun, and I stay solid all the same. What am I?Answer: The inner core. The inner core is solid, though it is about as hot as the Sun's surface.
I am a giant spark that jumps between a cloud and the ground. For an instant I heat the air around me to about 54,000 degrees Fahrenheit. What am I?Answer: Lightning. The air around a lightning flash heats to about 30,000 degrees Celsius, which is 54,000 degrees Fahrenheit.
I am a slow thief. Water, wind and ice are my helpers, and grain by grain they carry soil and rock away to somewhere else. What am I?Answer: Erosion. Erosion is the carrying away of soil and rock by water, wind or ice.
I am a thin layer of gas high above your head. I soak up most of the Sun's ultraviolet rays before they reach the ground. What am I?Answer: The ozone layer. The ozone layer absorbs most of the Sun's ultraviolet radiation.
I am a trip with no end. Water goes up from the sea, drifts over the land as cloud, comes down as rain and runs back along the rivers. What am I?Answer: The water cycle. The water cycle is the endless movement of water between sea, sky and land.
I am a wave, or a train of waves, set off by an earthquake under the sea. People once called me a tidal wave, though the tide has nothing to do with me. What am I?Answer: A tsunami. A tsunami is caused by a sudden shift of water, most often from an undersea earthquake.
I am one kind of storm with three names. In the Atlantic I am a hurricane, in the western Pacific a typhoon, and in the Indian Ocean a cyclone. What am I?Answer: A tropical cyclone. Hurricane, typhoon and cyclone are regional names for the same kind of storm.
I am rain that went down instead of away. I fill the cracks and spaces in the rock and soil under your feet, and a well is dug to reach me. What am I?Answer: Groundwater. Groundwater is the water held under the surface in rock and soil.
I am rock made in layers, from sand, mud and shells that settled and were pressed together. Most fossils are found in me. What kind of rock am I?Answer: Sedimentary rock. Sedimentary rock forms from layers of sediment, and it is where most fossils lie.
I am rock that used to be another kind of rock. Heat and pressure deep in the Earth changed me, the way limestone turns into marble. What kind of rock am I?Answer: Metamorphic rock. Metamorphic rock is older rock changed by heat and pressure.
I am rock that was once melted. I form when magma or lava cools and hardens, and granite and basalt are two of my kinds. What kind of rock am I?Answer: Igneous rock. Igneous rock forms when magma or lava cools.
I am the reason a cold glass is wet on the outside on a summer day. Water in the air touches the glass and turns back into drops. What am I?Answer: Condensation. Condensation is water vapor turning back into liquid water.
I am the reason a puddle is gone by the afternoon. Water turns into a gas you cannot see and rises into the air. What am I?Answer: Evaporation. Evaporation is a liquid turning into a gas at its surface.
I am the thickest layer of the Earth: hot rock that lies between the crust above and the core below. What am I?Answer: The mantle. The mantle makes up most of the Earth's volume.
I am the water in the air that you cannot see. When there is a lot of me, a hot day feels hotter, because the sweat on your skin is slow to dry. What am I?Answer: Humidity. Humidity is the amount of water vapor in the air, and high humidity slows the drying of sweat.
I begin deep underground at a point called the focus. The place on the surface right above it is my epicenter. What am I?Answer: An earthquake. The epicenter is the point on the surface straight above the focus.
Lightning heats the air so fast that the air bursts outward. I am the boom and rumble that burst makes. What am I?Answer: Thunder. Thunder is the sound of air expanding suddenly along a lightning bolt.
Rain is me. Snow is me. Sleet and hail are me too. I am the one word for any water that falls from the clouds. What am I?Answer: Precipitation. Rain, snow, sleet and hail are all forms of precipitation.
We are giant slabs of rock that fit together like the pieces of a cracked eggshell. The continents ride on us, and some of us creep along about as fast as a fingernail grows. What are we?Answer: Tectonic plates. The Earth's outer shell is broken into plates that move a few centimeters a year.
Weather is what today is like. I am what the weather of a place is like when you average it over about thirty years. What am I?Answer: Climate. Climate is the long-term pattern of weather, usually averaged over 30 years.
Matter, forces and energy 20
Everything you can touch is built of me, and I am far too small to see. My name comes from a Greek word for a thing that cannot be cut. What am I?Answer: An atom. Atom comes from the Greek atomos, uncuttable.
Heat and electricity pass through me easily. Copper is a very good one of me, and that is why wires are made of it. What am I?Answer: A conductor. A conductor lets electric current flow, and copper is one of the best.
I am a gas lighter than air, so a balloon full of me floats away. I was found in the light of the Sun before anyone found me on Earth, and I am named for the Sun. What gas am I?Answer: Helium. Helium was first seen in sunlight in 1868, and its name comes from helios, the Greek word for the Sun.
I am a metal, and at room temperature I am a silver liquid. For a long time I was the shining line inside a thermometer. What element am I?Answer: Mercury. Mercury is the only metal that is liquid at ordinary temperatures.
I am a vibration. I travel through air, through water and through walls, and I cannot cross empty space at all. What am I?Answer: Sound. Sound needs something to travel through, so it cannot cross a vacuum.
I am about one fifth of the air. Cover a candle with a glass jar, and the flame soon dies for lack of me. What gas am I?Answer: Oxygen. Air is about 21 percent oxygen, and burning needs it.
I am most of the air you are breathing: about 78 parts in every 100. Most people guess that oxygen has that honor. What gas am I?Answer: Nitrogen. Dry air is about 78 percent nitrogen.
I am not a thing that is hot. I am the energy that flows from a warmer thing to a cooler one, such as from the soup to the spoon. What am I?Answer: Heat. Heat is energy passing from a hotter body to a colder one.
I am the reason a stone sinks and a log floats, and the reason oil sits on top of water. I am how much stuff is packed into a space. What am I?Answer: Density. Density is mass divided by volume, and the less dense thing floats.
I am two atoms of hydrogen holding on to one atom of oxygen. A single raindrop holds more of me than you could ever count. What am I?Answer: A water molecule. Water is H2O: two hydrogen atoms and one oxygen atom.
I am why you tip forward when the bus stops. A thing that is moving keeps moving, and a thing at rest stays at rest, until a force steps in. What am I?Answer: Inertia. Inertia is the tendency of a thing to keep doing what it is doing.
I cannot be made and I cannot be destroyed. I can only change form, from motion to heat, or from sunlight to electricity. What am I?Answer: Energy. The law of conservation of energy says energy is neither created nor destroyed.
I have no shape of my own. Pour me into a glass and I am glass-shaped, pour me into a bowl and I am bowl-shaped, and there is just as much of me either way. What state of matter am I?Answer: A liquid. A liquid takes the shape of its container and keeps the same volume.
I keep my own shape wherever you put me. A rock is one of me, an ice cube is one of me, and so is the chair you sit on. What state of matter am I?Answer: A solid. A solid keeps its shape and its volume.
I pull everything toward the center of the Earth. I am why a dropped ball falls, and on the Moon I am only about one sixth as strong. What am I?Answer: Gravity. The pull of gravity at the Moon's surface is about one sixth of the Earth's.
I spread out to fill any container, whatever its size, and you can squeeze me into a smaller one. The air around you is made of me. What state of matter am I?Answer: A gas. A gas has no fixed shape or volume and fills its container.
In one form I am the soft gray tip of a pencil. In another I am a diamond, one of the hardest things known. What element am I?Answer: Carbon. Graphite and diamond are both pure carbon.
Rub a balloon on your hair, and I make the balloon stick to the wall. I am a charge that builds up and sits still until it finds somewhere to go. What am I?Answer: Static electricity. Static electricity is an electric charge that builds up on a surface.
Rub your hands together fast and you can feel me make heat. I am the force that slows a sliding box and lets your shoes grip the floor. What am I?Answer: Friction. Friction is the force that resists one surface sliding over another, and it makes heat.
You breathe me out, and green plants take me in. I am also the fizz in a can of soda. What gas am I?Answer: Carbon dioxide. Carbon dioxide is breathed out by animals, used by plants and put into fizzy drinks.
Tools and inventions 21
I am a guess that can be tested. A scientist writes me down before the experiment, and the experiment shows whether I hold up. What am I?Answer: A hypothesis. A hypothesis is a proposed explanation that an experiment can test.
I am a loop that electricity travels around. Break me at any point, and the light goes out. What am I?Answer: A circuit. Current flows only around a complete, closed circuit.
I am a machine that can be programmed to do a job by myself. My name comes from a Czech word for forced work, and it was first used in a play of 1920. What am I?Answer: A robot. The word robot comes from the Czech robota and was first used in a play.
I am a magnet you can turn off. Wind a wire around an iron nail and send a current through the wire, and I wake up. What am I?Answer: An electromagnet. An electromagnet is magnetic only while current flows through its coil.
I am a ramp wrapped around a rod. Turn me, and my ramp pulls me into the wood. What simple machine am I?Answer: A screw. A screw is an inclined plane wrapped around a cylinder.
I am a ring of small cups on top of a pole. The harder the wind blows, the faster I spin, and that is how the wind's speed is counted. What am I?Answer: An anemometer. A cup anemometer measures wind speed.
I am a stiff bar resting on a pivot. Push down on one end of me, and the other end lifts a load. A seesaw is one of me, and so is a crowbar. What simple machine am I?Answer: A lever. A lever is a beam that turns on a fixed point called a fulcrum.
I am a wheel with a groove in my rim and a rope running over me. Pull down on the rope, and the load on the other end goes up. What simple machine am I?Answer: A pulley. A pulley is a wheel that carries a rope or cable.
I am a wheel with teeth. My teeth fit between the teeth of another wheel like me, and when I turn one way, my neighbor turns the other. What am I?Answer: A gear. Two meshed gears turn in opposite directions.
I am the first working model of a new invention. I am built to be tested, broken and improved before the real ones are made. What am I?Answer: A prototype. A prototype is an early model built to test a design.
I am the plainest machine of all: a flat surface with one end higher than the other. Pushing a heavy box up me is easier than lifting it. What simple machine am I?Answer: An inclined plane. An inclined plane is a ramp, and it lets a smaller push raise a load.
I am two slopes back to back, meeting in a sharp edge. Drive me into a log, and I push it apart. The head of an ax is one of me. What simple machine am I?Answer: A wedge. A wedge turns a push on its blunt end into a split at its sharp end.
I have a north end and a south end. Cut me in half, and you do not get one of each: you get two of me, each with a north and a south. What am I?Answer: A magnet. A magnet always has two poles, and cutting it makes two smaller magnets.
I have a plus end and a minus end. Inside me, chemicals are waiting to be turned into electricity. What am I?Answer: A battery. A battery turns chemical energy into electrical energy.
I make far things look near. In 1610 one of me showed four moons circling Jupiter, which nobody had seen before. What am I?Answer: A telescope. Galileo found the four large moons of Jupiter with a telescope in 1610.
I measure the weight of the air pressing down on me. When my reading drops fast, a storm is likely on its way. What am I?Answer: A barometer. A barometer measures air pressure, and falling pressure often means bad weather.
I sit on a roof and turn sunlight straight into electricity. What am I?Answer: A solar panel. A solar panel turns light into electricity with photovoltaic cells.
I sit still and wait for the ground to move. When the waves of an earthquake pass under me, I record them as a wiggling line. What am I?Answer: A seismometer. A seismometer records the motion of the ground.
I use science and math to design bridges, engines and machines. The name of my job comes from a Latin word for cleverness. Who am I?Answer: An engineer. Engineer comes from the Latin ingenium, cleverness.
My name is built from Greek words for small and look. Put a very small thing under me, and it looks big enough to study. What am I?Answer: A microscope. Microscope comes from the Greek mikros, small, and skopein, to look.
We are a simple machine in two parts that turn together: a big round part and a thin rod through its middle. Turn either one of us, and the other has to turn too. What are we?Answer: A wheel and axle. In a wheel and axle the two parts are joined and turn together.