Science
3rd Grade TEKS — Scientific Practices, Matter, Forces, Earth & Organisms
🔭 Scientific Practices
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Key Concepts
- Observation: using your 5 senses to collect information. Measured data uses numbers and tools. Observed data describes what you see/hear/smell/touch.
- Hypothesis: a testable prediction. "If I water the plant more, then it will grow taller." It can be wrong — that's OK! Science learns from wrong answers too.
- Variable: what you change or measure in an experiment. Change one thing at a time. If you change two things, you can't tell which one caused the result.
- Repeated trials: running an experiment more than once makes results more reliable. One result could be an accident; three matching results are stronger evidence.
- Model limitations: a model is a smaller or simpler version of something real. It can't be exactly the same size, made of the same materials, or act exactly like the real thing.
- Tools: ruler (length) · thermometer (temperature) · balance (mass) · graduated cylinder/beaker (liquid volume) · spring scale (force) · hand lens (magnify) · stopwatch (time).
- Safety: always wear goggles when using chemicals or heat. Never taste unknown substances. Wash hands after experiments.
- Plan and conduct investigations; ask questions and make observations
- Collect, measure, and record data using metric units
- Organize data into tables, charts, and bar graphs
- Analyze data and draw reasonable conclusions from evidence
- Understand that repeated tests increase reliability
- Know the limitations of models (size, materials, properties)
- Practice lab safety: goggles, gloves, proper disposal
⚗️ Matter and Energy
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Key Concepts
- Solid: has a definite (fixed) shape and definite volume. Does NOT change shape on its own. Examples: rock, ice, pencil.
- Liquid: has a definite volume but NO fixed shape — it takes the shape of its container. Examples: water, juice, lava.
- Gas: has NO fixed shape and NO fixed volume — it expands to fill any container. Examples: air, steam, helium in a balloon.
- Heating causes: melting (solid → liquid) and evaporation (liquid → gas).
- Cooling causes: condensation (gas → liquid) and freezing (liquid → solid).
- Physical properties you can measure: temperature · mass (use a balance) · magnetism (test with a magnet) · ability to sink or float (put in water).
- Mixture: two or more substances combined. Examples: gravel + sand, trail mix, metal + plastic clips. The substances can still be separated.
Watch & Learn
Crash Course Kids — What's Matter? (States of Matter)
Crash Course Kids — What's My Property?
- Describe and classify matter as solid, liquid, or gas
- Measure physical properties: temperature, mass, magnetism, sink/float
- Predict changes in state caused by heating or cooling
- Explore mixtures — two or more materials combined
⚡ Force, Motion, and Energy
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Key Concepts
- Force: a push or a pull. Forces change the motion of objects — they can make things start moving, stop moving, speed up, slow down, or change direction.
- Gravity: a force that pulls all objects toward Earth. No matter where you are on Earth, gravity pulls you downward. The bigger the mass, the stronger the gravity.
- More force = more motion. Throwing a ball harder makes it go farther. Pushing a heavier object requires more force than pushing a lighter one.
- Magnetism: like poles repel (N↔N, S↔S push apart) · opposite poles attract (N↔S pull together). Magnets attract iron, nickel, cobalt — not plastic or wood.
- Forms of energy: Mechanical (motion) · Thermal/heat (warmth) · Light (radiant) · Sound (vibrations we hear) · Electrical (flowing through wires).
- Energy example — guitar: plucking the string creates mechanical energy (movement) → the vibrating string creates sound energy (waves in the air).
Watch & Learn
Crash Course Kids — Defining Gravity
Crash Course Kids — Gravity Compilation
- Identify forms of energy: mechanical, light, sound, heat/thermal
- Understand that pushing and pulling changes position and motion
- Observe how gravity pulls objects toward Earth
- Understand magnetism — like poles repel, opposite poles attract
- Greater force = greater change in motion
🌍 Earth and Space
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Key Concepts
- Planets in order from the Sun (mnemonic): My Very Educated Mother Just Served Us Nachos → Mercury · Venus · Earth · Mars · Jupiter · Saturn · Uranus · Neptune.
- Earth's motions: Rotation = spinning on its axis → causes day and night (24 hours). Revolution = orbiting the Sun → causes seasons and the year (365 days).
- Moon: orbits Earth approximately every 28 days. Does NOT produce light — it reflects sunlight.
- The Sun: a star made of hot gases (hydrogen & helium). Provides light and heat energy that drives the water cycle.
- Water cycle: Sun heats water → evaporation (liquid → vapor) → vapor cools → condensation (clouds form) → precipitation (rain/snow falls).
- Soil formation: weathering (wind, water, freeze/thaw breaks rock) + decomposition (dead plants and animals break down) = soil over millions of years.
- Rapid Earth changes: volcanic eruption · earthquake · landslide · flood · hurricane. These can reshape landscapes quickly.
- Landforms: mountain (tall, peaked) · hill (shorter, rounded) · valley (low land between hills/mountains) · plain (large flat area) · plateau (high flat land) · delta (fan-shaped deposit at a river's mouth).
Watch & Learn
Crash Course Kids — The Water Cycle
Crash Course Kids — Landforms, Hey!
Crash Course Kids — Weather vs. Climate
Crash Course Kids — Earth's Orbit Around the Sun
- Know soil forms through weathering of rock + decomposition of organisms
- Identify rapid Earth changes: volcanoes, earthquakes, landslides
- Identify landforms: mountains, hills, valleys, plains
- Measure and record weather: temperature, wind direction, precipitation
- Understand the Sun as a star that powers the water cycle
- Know Earth orbits the Sun and the Moon orbits Earth
- Name the 8 planets in order from the Sun
🌿 Organisms and Environment
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Key Concepts
- Food chain: shows the flow of energy from one organism to the next. Energy flows in ONE direction: Producer → Primary Consumer → Secondary Consumer → Decomposer.
- Producers: plants — they make their own food using sunlight (photosynthesis). Consumers eat other organisms. Decomposers (fungi, worms, bacteria) break down dead things.
- Food web: many overlapping food chains in an ecosystem. Remove one species → the whole web is affected. Example: remove frogs → tadpoles increase, herons decrease.
- Adaptation: a physical trait or behavior that helps an organism survive in its environment. Examples: polar bear (thick fur for cold) · cactus (stores water for desert) · duck (webbed feet for swimming).
- Inherited trait: you are BORN with it — it comes from your parents' genes. Examples: eye color, number of legs, flower color.
- Learned behavior: developed through experience or practice. Examples: dog sitting on command, bird learning a new migration route.
- Life cycles: Butterfly: egg → caterpillar (larva) → chrysalis (pupa) → butterfly (adult). This is complete metamorphosis. Frog: egg → tadpole → froglet → adult frog. Chicken/sea turtle: egg → hatchling → juvenile → adult.
- Environmental change: drought → water-storing plants survive, others die. Flood → fire ants form a raft and float to a new location.
Watch & Learn
Crash Course Kids — Fabulous Food Chains
Crash Course Kids — Home Sweet Habitat
Crash Course Kids — Living Things Change (Adaptations)
Crash Course Kids — The Dirt on Decomposers
- Describe environments and the populations within an ecosystem
- Identify the flow of energy in a food chain
- Predict how changes in a food chain affect the ecosystem
- Distinguish inherited traits from learned behaviors
- Describe life cycles of various organisms
- Explain how adaptations help organisms survive