Grade 9 Science Vocabulary Flashcards

Flashcards for Grade 9 Science Review

LD50

Lethal Dose 50; the amount of a substance required to kill 50% of a test population, used to measure the acute toxicity of a substance. Measured in mg/kg

Corrosion

The process by which metals are oxidized, leading to their deterioration. A common example is the rusting of iron, where iron reacts with oxygen and water to form iron oxide (Fe2O3).

Law of Electric Charges

States that like charges repel each other, and unlike charges attract each other. This principle underlies all electrical phenomena.

Doppler Effect

The change in wavelength of a wave (light or sound) due to the motion of the source or the observer. A red shift indicates movement away (longer wavelength), while a blue shift indicates movement towards (shorter wavelength).

Space junk

Debris from defunct satellites, rockets, and other spacecraft components orbiting Earth. It poses a significant collision risk to operational spacecraft and satellites.

Structural adaptations

Physical traits that enhance survival and reproduction in a specific environment (e.g., camouflage, beak shape).

Behavioral adaptations

Learned or instinctive actions that improve an organism's survival and reproduction (e.g., migration, hibernation).

Natural selection

The process by which organisms best suited to their environment survive and reproduce at a higher rate than less well-adapted organisms. This leads to evolutionary changes in populations over time.

Mutation

A change in the DNA sequence of an organism. Mutations can be beneficial (leading to new adaptations), harmful (causing diseases), or neutral (having no effect).

pH scale

A scale used to specify the acidity or basicity of an aqueous solution. It ranges from 0 to 14, with values less than 7 indicating acidity, values greater than 7 indicating basicity, and 7 indicating neutrality. pH is defined as pH = -log_{10}[H^+], where [H^+] is the concentration of hydrogen ions.

Acid rain

Rain with a pH less than 5.6, caused by the presence of pollutants such as sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon dioxide (CO_2) in the atmosphere, which react with water to form acids.

Bioaccumulation/biomagnification

The process by which substances, such as pesticides or heavy metals, accumulate in living organisms as they move up the food chain. Top predators are most affected due to the concentration of these substances in their prey.

Law of Conservation of Mass

States that mass is neither created nor destroyed in ordinary chemical reactions. The total mass of the reactants equals the total mass of the products.

Chemical formula

A notation that shows the types of elements and the number of atoms of each element in a molecule (e.g., water is H_2O, indicating two hydrogen atoms and one oxygen atom).

Algal bloom

A rapid increase in the population of algae in an aquatic system, often caused by excessive nutrients like nitrogen or phosphorus from agricultural runoff or pollution. This can lead to oxygen depletion and harm aquatic life.

Biodegradability

The ability of a substance to be broken down by microorganisms into simpler substances. Biodegradability is affected by factors such as temperature which increases the rate of degradation by organisms, and presence of moisture.

Biological diversity

The variety of life in a specific area, encompassing species diversity (number of different species), genetic diversity (variation within species), and ecosystem diversity (variety of habitats and ecological processes).

Niche

The role an organism plays in its environment, including its habitat, what it eats, how it interacts with other organisms, and its behavior.