Year 9 Science Exam Review

Comprehensive practice flashcards covering Scientific Investigation, Chemistry, Biology, Reproduction, Energy, Carbon Cycle, Waves, Disease, and Space Exploration for Year 9 Science.

In experimental design, what do the terms IV, DV, and CV stand for and represent?

IV (Independent Variable) is what is being changed, DV (Dependent Variable) is what is measured, and CV (Controlled Variable) represents variables that can impact the DV but are kept the same throughout.

What is an extraneous variable (EV), and why is it important to address in an experiment?

An EV is a variable that will or has a likelihood to impact the DV other than the IV; turning EVs into CVs is important to ensure a fair experiment.

What is the distinction between accuracy and precision in scientific data?

Accuracy refers to how close a measured result is to the real result, whereas precision refers to how close repeated results are to each other.

How do internal validity and external validity differ?

Internal validity refers to how well variables are controlled and the IV is measured, while external validity refers to how results can be generalised or applied to real-world settings.

What three elements must be stated when formulating a scientific conclusion?

A conclusion must state the IV, the DV, and the observed trend.

What are the charges and relative masses of protons, neutrons, and electrons?

Protons have a positive charge ($+$), neutrons have no charge, and electrons have a negative charge ($-$) and very little mass.

How are atomic number and mass number determined for an atom?

Atomic number equals the number of protons, while mass number equals protons plus neutrons ($\text{Protons} + \text{Neutrons}$).

What are isotopes?

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

What is radioactivity, and what are radioisotopes?

Radioactivity is the process where unstable nuclei fall apart through nuclear decay; isotopes that undergo decay are called radioisotopes.

What are the physical natures of alpha, beta, and gamma radiation?

Alpha radiation is a fast-moving helium nucleus; beta radiation is a highly energised electron or positron with no mass; gamma radiation is a very high energy photon of electromagnetic radiation.

How does reactivity change as you move down groups in the periodic table for metals versus non-metals?

As you move down a group, metal reactivity increases and non-metal reactivity decreases.

How does the octet rule dictate whether an atom will lose or gain electrons to form an ion?

Atoms change to fill their valence shell: atoms with 3 or fewer valence electrons lose electrons to form an ion, atoms with 5 or more gain electrons, and atoms with 4 could go either way.

What type of attraction holds ionic compounds together, and what is their net charge?

They are held together by electrostatic attraction between oppositely charged ions (cations and anions), resulting in an overall neutral charge.

How are variable charge cations named in ionic compounds, such as $Sn^{2+}$ and $Sn^{4+}$?

The cation name includes Roman numerals to indicate the charge: $Sn^{2+}$ is Tin (II) and $Sn^{4+}$ is Tin (IV).

What structural and physical properties characterize ionic compounds?

They form a crystal lattice, are solid at room temperature, are brittle, and have high melting points.

What is the structural hierarchy of biological organization in multicellular organisms?

$$\text{Cells} \rightarrow \text{Tissues} \rightarrow \text{Organs} \rightarrow \text{Organ systems} \rightarrow \text{Organisms}$$

What biological structure is depicted in this diagram, and what are its key labelled components?

A neuron (nerve cell), comprising dendrites, cell body with nucleus, axon, myelin sheath, Schwann cells, nodes of Ranvier, and axon terminals.

What is the sequence of signal transmission through a neuron and across a synapse?

Message received at dendrites $\rightarrow$ passes through cell body $\rightarrow$ travels down axon to axon terminals $\rightarrow$ release of neurotransmitters across the synaptic gap $\rightarrow$ binding to receptors on the next dendrite.

What is the neural pathway of a spinal reflex arc?

$$\text{Stimulus} \rightarrow \text{Sensory neuron} \rightarrow \text{Spinal Interneuron} \rightarrow \text{Motor neuron} \rightarrow \text{Muscle}$$

What are the specific roles of sensory neurons, interneurons, and motor neurons?

Sensory neurons receive and carry sensory information; interneurons transmit and relay information solely within the CNS; motor neurons carry messages from the brain and spinal cord to skeletal muscles.

How do hormones travel through the body and act on their target cells?

Hormones are chemical messengers secreted by glands that travel through the bloodstream and bind to target cells using a lock-and-key mechanism.

What roles do the hypothalamus and pituitary gland play in the endocrine system?

The hypothalamus connects the brain to the hormonal system and releases hormones to control the pituitary gland; the pituitary gland is the master gland that regulates many other endocrine glands.

How do insulin and glucagon work together to maintain blood glucose homeostasis?

Produced by the pancreas, insulin lowers blood glucose by promoting its uptake, while glucagon raises blood glucose by stimulating its release from storage in the liver.

What is the function of a negative feedback loop in homeostasis?

A negative feedback loop counteracts any deviation in a variable to return the body back to its stable starting set point.

How do sexual and asexual reproduction differ in terms of parents and offspring?

Sexual reproduction involves two parents whose gametes unite to form unique offspring; asexual reproduction involves a single parent producing an identical genetic clone.

What are binary fission, budding, and fragmentation in asexual reproduction?

Binary fission is a parent cell splitting into two clones; budding is when a small bud develops and breaks off into a clone; fragmentation is when a broken piece of an organism develops into a complete organism.

What are the components of the male (stamen) and female (pistil) parts of a flower?

The stamen consists of the anther and filament; the pistil consists of the stigma, style, ovary, and ovules.

How do r-selected species differ from K-selected species regarding offspring and parental care?

r-species produce high numbers of offspring with low parental care, fast growth, and small bodies; K-species produce low numbers of offspring with high parental care, slow growth, and large bodies.

In human female reproduction, where does fertilisation take place and where does the embryo develop?

Fertilisation occurs in the fallopian tube, while the embryo and foetus develop inside the uterus.

What is the formula used to calculate energy efficiency?

$$\text{Efficiency (\%)} = \frac{\text{Useful Output Energy}}{\text{Total Input Energy}} \times 100$$

How is mechanical work defined and calculated mathematically?

Work is the measure of energy transfer when an object is moved a distance by an external force; calculated as $\text{Work} = \text{Force} \times \text{Distance}$.

What are the chemical equations for photosynthesis and aerobic cellular respiration?

Photosynthesis: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$; Respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}$.

What is a carbon sink, and what are three examples?

A carbon sink is a natural or artificial reservoir that absorbs more $CO_2$ than it produces, such as soil, forests, or the ocean.

How do oceanic lithosphere and continental lithosphere differ?

Oceanic lithosphere contains the uppermost layers of the mantle with a thin yet heavy crust, whereas continental lithosphere has a thick yet light crust.

How do particles oscillate in longitudinal waves compared to transverse waves?

In longitudinal waves, particles oscillate parallel to the direction of energy transfer (forming compressions and rarefactions); in transverse waves, the disturbance is perpendicular to the wave's direction of travel.

In sound waves, how are pitch and volume related to wave characteristics?

Pitch corresponds to wave frequency, and volume corresponds to wave amplitude.

What is the order of electromagnetic waves from longest to shortest wavelength?

Radio waves $\rightarrow$ Microwaves $\rightarrow$ Infrared $\rightarrow$ Visible light $\rightarrow$ UV $\rightarrow$ X-rays $\rightarrow$ Gamma rays.

Which major types of pathogens are cellular, and which are non-cellular?

Bacteria, fungi, and parasites are cellular pathogens; viruses are non-cellular pathogens.

How do the body's first and second lines of defence combat pathogens?

The first line uses physical barriers (skin, nose hairs, tears); the second line uses non-specific phagocytosis by macrophages and neutrophils, accompanied by swelling and fever.

What are the roles of B cells and cytotoxic T cells in the third line of defence?

B cells produce antibodies that bind to pathogen antigens via a lock-and-key mechanism; cytotoxic T cells identify and destroy infected host cells displaying foreign antigens.

How are an outbreak, an epidemic, and a pandemic distinguished?

An outbreak is a sudden increase in infection in a local population; an epidemic is more widespread across a region; a pandemic spreads cross-continentally.

How does Newton's Third Law govern rocket launch and propulsion?

Rocket engines expel exhaust gases downwards at high speed, creating an equal and opposite upward reaction force (thrust) that overcomes gravity and weight.

What four approaches are used to build better rockets?

Improved propellant, multistage rockets, additive manufacturing, and recovery and reuse.

What are the orbital periods and altitude characteristics of LEO, MEO, and GEO satellites?

LEO is $<100\,\text{km}$ with an orbital period of $128\,\text{minutes}$ or less; MEO has a period of $>128\,\text{minutes}$ and $<1\,\text{day}$; GEO has an orbital period of $23\,\text{h}\;56\,\text{min}$, matching Earth's rotation.