Year 9 End-of-Year Science Revision

Comprehensive practice flashcards covering Year 9 Science topics including Physics (Forces, Waves, Energy), Biology (Genetics, Health, Differentiation), and Chemistry (Periodic Table, Mixtures).

What is the difference between a scalar and a vector quantity?

Scalar quantities only have a magnitude (size), such as speed, distance, mass, energy, power, time, and temperature. Vector quantities have both magnitude and direction, such as velocity, displacement, acceleration, force, weight, and momentum.

How is acceleration related to force and mass according to Newton’s 2nd Law?

Acceleration increases if the resultant force on an object increases, and acceleration decreases if the mass of the object increases. Friction/Force is calculated as $\text{Force} (N) = \text{mass} (kg) \times \text{acceleration} (m/s^2)$. ($F = m \times a$)

State Newton’s 3rd Law of Motion.

Whenever two objects interact, the forces they exert on each other are equal in size and opposite in direction. For every action, there is an equal and opposite reaction.

What is the formula for calculating Weight?

$\text{Weight} (N) = \text{Mass} (kg) \times \text{gravitational field strength} (N/kg)$. For instance, on Earth, gravity measures $9.8\,N/kg$ (or $10\,N/kg$ for simpler calculations).

How is Density defined and calculated?

Density is mass per unit volume. It is calculated using the formula $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$. Standard units are $kg/m^3$ or $g/cm^3$.

Describe the method to find the density of an irregular-shaped object.

1. Find the mass of the solid using a balance. 2. Fill a Eureka can with water until it overflows. 3. Place a measuring cylinder under the spout, add the irregular object, and collect and measure the volume of the displaced runoff. 4. Calculate density by dividing mass by volume.

What is the formula for Pressure?

$\text{Pressure} = \frac{\text{Force}}{\text{Area}}$, where Force is in Newtons ($N$) and Area is in meters squared ($m^2$). The outcome is measured in Pascals ($Pa$), where $1\,N/m^2 = 1\,Pa$.

What determines if an object will float or sink in water?

The object's density compared to water ($1\,g/cm^3$). If the density is less than 1, the object floats; if it is more than 1, it sinks.

What are the three stages of the cell cycle (Mitosis)?

1. Growth phase: Cell grows, DNA replicates, and organelles like ribosomes and mitochondria increase. 2. Mitosis: Chromosomes line up in the middle and are pulled to opposite ends; two nuclear membranes form. 3. Cytokinesis: Cytoplasm and cell membrane divide to form two genetically identical daughter cells.

What is a stem cell and how are human stem cells categorized?

Stem cells are undifferentiated cells that can differentiate to form specialized cells. Human stem cells come from Adult stem cells (e.g., bone marrow, can differentiate into some cells) or Embryonic stem cells (can turn into any type of specialized cell).

How does the nervous system transmit information across a synapse?

A synapse is a small gap between two neurones. When an electrical impulse reaches the end of the first neurone, a chemical is released. This chemical diffuses across the synapse and attaches to the second neurone, triggering another electrical impulse.

Define an Isotope.

Atoms of the same element that have the same number of protons but a different number of neutrons.

How is the Relative Atomic Mass ($A_r$) calculated for an element with isotopes?

It is an average value taking into account the abundance of isotopes. Calculated as: $A_r = \frac{\sum (\text{isotope mass} \times \text{abundance})}{\sum \text{total abundance}}$. For example, Chlorine ($35.5$) and Lithium ($6.92$).

Contrast the Plum Pudding Model with the Nuclear Model of the atom.

The Plum Pudding model (Thomson) suggested the atom is a ball of positive charge with negative electrons embedded in it. The Nuclear model (Rutherford) suggested electrons orbit a nucleus, while Bohr refined this to show electrons orbit at set energy levels (shells).

How did Mendeleev develop the Periodic Table?

He organized elements by increasing atomic mass and grouped them by properties. He left gaps for undiscovered elements and switched the order of some elements to ensure chemically similar elements fell into the same columns.

What factors affect the rate of diffusion?

1. Temperature (higher kinetic energy increases speed). 2. Concentration difference (greater difference increases speed). 3. Surface area (larger area increases speed). 4. Diffusion distance (shorter distance increases speed).

Compare the structures of Arteries, Veins, and Capillaries.

Arteries have thick muscular walls and a small lumen to carry blood at high pressure away from the heart. Veins have thin walls, a large lumen, and valves to prevent backflow as they carry blood to the heart. Capillaries are one cell thick to allow for short diffusion distances.

What are the products of anaerobic respiration in muscles and in yeast?

In muscles, glucose produces lactic acid. In plants and yeast cells (fermentation), glucose produces ethanol and carbon dioxide.

Define Communicable disease and name the four types of pathogens.

A communicable disease is one that can be spread from person to person by a pathogen. Pathogens include Bacteria, Viruses, Protists, and Fungi.

How do vaccines work to provide immunity?

A small amount of dead or inactive pathogen is injected. White blood cells detect the antigens and produce antibodies. Memory white blood cells are created so that if the live pathogen re-enters, antibodies are mass-produced quickly to prevent re-infection.

What are the rules for identifying energy stores using the 'GEEKSLUNCH' acronym?

Gravitational potential, Elastic potential, Electrostatic, Kinetic, Sound, Light, Nuclear, Chemical, and Heat (Thermal).

What is the Law of Conservation of Energy?

Energy cannot be created or destroyed; it can only be transferred from one store to another.

Differentiate between renewable and non-renewable energy resources.

Renewable resources (e.g., solar, wind, geothermal, bio-fuels, hydroelectric) can be replaced as they are used and will not run out. Non-renewable resources (e.g., fossil fuels, nuclear) are not replenished quickly and will run out.

How is the $R_f$ value calculated in chromatography?

$R_f = \frac{\text{distance moved by substance}}{\text{distance moved by solvent}}$. The value is always between 0 and 1.

Explain the difference between genotype and phenotype.

Genotype is the combination of alleles an individual has (e.g., $BB$ or $Bb$). Phenotype is the physical characteristic expressed (e.g., black fur).

Contrast homozygous and heterozygous alleles.

Homozygous means the alleles for a gene are the same (e.g., $BB$ or $bb$). Heterozygous means the alleles for a gene are different (e.g., $Bb$).

Describe the difference between abiotic and biotic factors in an ecosystem.

Abiotic factors are non-living (e.g., light intensity, temperature, soil pH, moisture). Biotic factors are living (e.g., food availability, new predators, pathogens, outcompeting species).

Compare Transverse and Longitudinal waves.

Transverse waves oscillate perpendicular to the direction of energy transfer (e.g., light, water ripples). Longitudinal waves oscillate parallel to the direction of energy transfer and consist of compressions and rarefactions (e.g., sound waves).

What is the wave speed formula?

$\text{Wave speed} (m/s) = \text{Frequency} (Hz) \times \text{Wavelength} (m)$. ($v = f \times \lambda$)

Explain refraction using the 'TAGAGA' rule.

Refraction occurs when light changes speed between substances. 'TAG' stands for 'Towards (Normal) when moving from Air to Glass'. 'AGA' stands for 'Away (from Normal) when moving from Glass to Air'.