Grade 7 Science and Technology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Independent variable

The single factor an investigator deliberately changes in an experiment so that its effect on the measured outcome can be observed.

Control group

The comparison group in an experiment that receives no treatment or a standard treatment, showing what would happen without the tested factor.

Accuracy versus precision

Accuracy is how close a measurement is to the true value; precision is how close repeated measurements are to one another.

Hypothesis

A testable, falsifiable prediction about the relationship between variables, stated before data collection and judged against the results.

Density

Mass per unit volume of a substance, calculated as mass divided by volume, commonly expressed in grams per cubic centimetre.

Chemical change

A change in which new substances form with different properties, often shown by colour change, gas, precipitate, or temperature change.

Distillation

A separation method that boils a liquid mixture and condenses the vapour, separating substances with different boiling points.

Conservation of mass

In a closed system, the total mass of reactants equals the total mass of products because atoms are rearranged, not created or destroyed.

pH scale

A scale from 0 to 14 measuring acidity: below 7 is acidic, 7 is neutral, and above 7 is basic or alkaline.

Inertia

The tendency of an object to resist changes in its motion, so it stays at rest or moves uniformly unless a net force acts.

Newton's second law

The net force on an object equals its mass multiplied by its acceleration, so acceleration grows with force and shrinks with mass.

Kinetic energy

The energy an object has because of its motion, calculated as one half times mass times velocity squared.

Power

The rate at which work is done or energy is transferred, calculated as work divided by time and measured in watts.

Cell theory

The principle that all living things are made of cells, cells are the basic unit of life, and new cells come from existing cells.

Mitochondria

Organelles that release usable energy from glucose through respiration; cells with high energy demands, such as muscle cells, contain many.

Alveoli

Tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out, greatly increasing surface area.

Villi

Finger-like projections lining the small intestine that increase surface area for absorbing digested nutrients into the blood.

Carrying capacity

The maximum population size an ecosystem can sustain over time given available food, water, shelter, and other limiting resources.

Food web

A diagram of interconnected food chains showing how energy moves among many producers, consumers, and decomposers in an ecosystem.

Decomposers

Organisms such as fungi and bacteria that break down dead organisms and waste, releasing nutrients back into the soil for reuse.

Biodiversity

The variety of life at genetic, species, and ecosystem levels; higher biodiversity generally makes ecosystems more resilient to change.

Mutualism

A symbiotic relationship in which both species benefit, such as flowers supplying nectar while insects carry pollen between plants.

Seasons

Annual changes in sunlight angle and day length caused by Earth's tilted axis as it revolves around the Sun, not by distance from the Sun.

Moon phases

The changing visible shape of the Moon caused by the shifting angle between Earth, Moon, and Sun during a cycle of about 29.5 days.

Igneous rock

Rock formed when molten magma or lava cools and solidifies; slow cooling underground produces large crystals, fast cooling produces small ones.

Water cycle

The continuous movement of water through evaporation, transpiration, condensation, precipitation, runoff, and collection, powered mainly by the Sun.

Weather versus climate

Weather is the short-term state of the atmosphere; climate is the long-term average pattern of temperature and precipitation in a region.

Prototype

An early working model of a design, built and tested to reveal problems before committing resources to full production.

Design constraints

Limits on a solution such as budget, available materials, time, size, safety rules, and environmental impact that the design must respect.

Trade-off

A compromise in which improving one feature of a design, such as strength, makes another feature, such as weight or cost, worse.

Renewable resource

A natural resource such as sunlight, wind, or biomass that is replenished by natural processes within a human lifetime.

Peer review

Independent expert evaluation of a study's methods and conclusions before publication, helping filter errors and unsupported claims.