The scientific method
Scientists answer questions by testing ideas. Follow the same steps they do:
- Ask a question you can test.
- Predict what you think will happen (a hypothesis).
- Test with a fair experiment, changing only one thing.
- Record what you observe and measure.
- Explain what the results show, then share them.
Living things
Living things grow, need energy, respond to their surroundings and reproduce.
Plants
Use sunlight, water and carbon dioxide to make food. This process is photosynthesis.
Animals
Eat other living things. Groups include mammals, birds, reptiles, amphibians, fish and insects.
Fungi
Mushrooms and molds break down dead material and return nutrients to the soil.
Food chain
Sun → grass → rabbit → fox. Energy flows from producers (plants) to consumers (animals), and decomposers recycle what is left.
Life cycle of a butterfly
Egg, caterpillar (larva), chrysalis (pupa), adult butterfly. This is complete metamorphosis.
Matter and energy
Matter is anything that has mass and takes up space. It usually exists in three states.
| State | Shape | Particles |
|---|---|---|
| Solid | Fixed shape | Packed tightly, vibrating in place |
| Liquid | Takes shape of its container | Close together, able to slide |
| Gas | Fills the whole container | Far apart, moving fast |
Adding heat melts ice into water and boils water into steam. Removing heat reverses it.
Forms of energy
Light, heat, sound, motion and electricity are all forms of energy. Energy can change form but is never used up.
Forces and motion
A force is a push or a pull. Forces can start, stop or change the direction of motion.
- Gravity pulls objects toward Earth.
- Friction slows things that rub together.
- Magnetism attracts iron and steel.
Earth and space
| Planet | Fact |
|---|---|
| Mercury | Closest to the Sun |
| Venus | Hottest planet |
| Earth | Only known planet with life |
| Mars | Red from iron-rich dust |
| Jupiter | Largest planet |
| Saturn | Famous bright rings |
| Uranus | Tilted on its side |
| Neptune | Farthest from the Sun |
Why we have day, night and seasons
Earth spins once about every 24 hours, giving us day and night. Its tilt as it orbits the Sun for a year causes the seasons.
The water cycle
Evaporation lifts water into the air, condensation forms clouds, precipitation brings rain or snow, and collection gathers water in rivers, lakes and oceans.
The human body
Pumps blood around the body.
Bring in oxygen and release carbon dioxide.
Controls thoughts, movement and senses.
Supports and protects the body. Adults have 206 bones.
Try at home
Rainbow in a glass
Fill a glass with water, set it in sunlight on a table, and put a sheet of white paper beside it. Light bends as it passes through the water and splits into colors.
Sink or float
Collect a coin, a cork, a grape and a paperclip. Predict which float, then test. Record your results in a table.
Baking soda volcano
Put 2 tablespoons of baking soda in a cup, then pour in vinegar. The reaction makes carbon dioxide gas bubbles. Do this outside or in a sink with an adult.