Elementary Education: Science Content Knowledge Flashcards

What is photosynthesis?

Answer: The process by which plants use sunlight, water, and carbon dioxide to produce glucose and oxygen

Photosynthesis is the biological process in which plants (and some other organisms) use light energy to convert CO₂ and water into glucose and oxygen.

Which of Newton's laws states that an object at rest remains at rest unless acted upon by an outside force?

Answer: Newton's First Law (Law of Inertia)

Newton's First Law (Law of Inertia) states that an object will remain in its current state of motion unless acted upon by an unbalanced external force.

What are the three states of matter, and what distinguishes them at the molecular level?

Answer: Solid, liquid, gas; distinguished by particle arrangement, energy, and intermolecular spacing

The three common states of matter differ in how their particles are arranged and how much energy they have: solids (tightly packed, vibrate in place), liquids (close but mobile), gases (far apart, move freely).

What is the difference between a food chain and a food web?

Answer: A food chain shows a single path of energy flow; a food web shows multiple interconnected paths

A food chain is a linear sequence showing one path of energy transfer. A food web shows the complex, interconnected network of multiple overlapping food chains.

What causes the seasons on Earth?

Answer: The tilt of Earth's axis as it orbits the Sun

Earth's axial tilt (about 23.5°) causes the seasons. As Earth orbits the Sun, different hemispheres are tilted toward or away from the Sun, changing sunlight intensity and duration.

Which of the following is an example of a physical change?

Answer: Cutting paper into pieces

Cutting paper changes the shape and size but not the chemical composition — it is a physical change. Burning, rusting, and baking all produce new substances (chemical changes).

What is the role of decomposers in an ecosystem?

Answer: They break down dead organisms and recycle nutrients back into the environment

Decomposers (fungi, bacteria) break down dead organic matter, releasing nutrients back into the soil and environment, completing the nutrient cycle.

What is the difference between a hypothesis and a theory in science?

Answer: A hypothesis is a testable prediction; a theory is a well-substantiated explanation supported by extensive evidence.

A hypothesis is a specific, testable prediction for an experiment. A scientific theory is a well-supported explanation that has withstood repeated testing and is supported by large bodies of evidence.

What is the water cycle, and what are its main stages?

Answer: Evaporation → condensation → precipitation → runoff/infiltration

The water cycle describes the continuous movement of water: evaporation (liquid → vapor), condensation (vapor → droplets/clouds), precipitation (rain/snow), and runoff/infiltration back to oceans and groundwater.

What is the function of mitochondria in a cell?

Answer: To generate energy (ATP) through cellular respiration

Mitochondria are the 'powerhouses of the cell' — they produce ATP (energy) through cellular respiration by breaking down glucose in the presence of oxygen.

What is the electromagnetic spectrum, and how is it ordered?

Answer: From longest wavelength/lowest energy to shortest wavelength/highest energy: radio → infrared → visible → ultraviolet → X-ray → gamma

The electromagnetic spectrum is ordered from longest wavelength/lowest frequency/lowest energy (radio waves) to shortest wavelength/highest frequency/highest energy (gamma rays).

What is the difference between weathering and erosion?

Answer: Weathering breaks down rock in place; erosion is the transportation of weathered material.

Weathering is the breakdown of rock in place (chemical or mechanical). Erosion is the removal and transport of weathered material by water, wind, ice, or gravity.

Which of the following correctly describes the process of natural selection?

Answer: Organisms with traits better suited to their environment tend to survive and reproduce more, passing those traits on.

Natural selection: individuals with heritable traits better suited to their environment are more likely to survive and reproduce, increasing the frequency of those traits over generations.

What is the difference between an element and a compound?

Answer: An element contains only one type of atom; a compound contains two or more types of atoms chemically bonded together.

An element is a pure substance with only one kind of atom (e.g., oxygen, gold). A compound is a substance formed when two or more elements are chemically bonded in fixed ratios (e.g., water = H₂O).

What is the law of conservation of energy?

Answer: Energy cannot be created or destroyed; it can only be transformed from one form to another.

The law of conservation of energy states that the total energy in a closed system remains constant — energy cannot be created or destroyed, only converted between forms.

What is the difference between a renewable and a nonrenewable energy resource?

Answer: Renewable resources are replenished naturally at a rate comparable to use; nonrenewable resources take millions of years to form.

Renewable resources (solar, wind, water, geothermal, biomass) are naturally replenished on human timescales. Nonrenewable resources (coal, oil, natural gas) took millions of years to form and are depleted much faster than they regenerate.

What happens to light when it passes from air into a denser medium such as water?

Answer: It slows down and bends toward the normal (refraction).

When light enters a denser medium, it slows down and bends toward the normal — this is refraction. It causes the apparent bending of objects in water.

What is the function of the nucleus in a cell?

Answer: To contain and protect the cell's DNA, controlling the cell's activities and reproduction

The nucleus is the control center of the cell — it contains the DNA (genetic information) that directs cell activities, protein synthesis, and reproduction.

What is the difference between inherited and acquired traits?

Answer: Inherited traits are passed from parents through genes; acquired traits are developed through experience or environment.

Inherited traits are encoded in DNA and passed from parents to offspring. Acquired traits develop through experience, learning, or environmental influence and are not passed to offspring genetically.

Which layer of Earth is the thickest?

Answer: Mantle

The mantle is Earth's thickest layer, extending about 2,900 km (1,800 miles) from the base of the crust to the outer core.