Year 7 Science Comprehensive Study Guide

Hypothesis: A prediction about how something will work, made before an experiment is conducted.
Conclusion: A statement written at the end of an experiment. It is used to discuss whether the initial hypothesis was correct. If the hypothesis was not correct, this statement should include possible reasons for the discrepancy.
Dependent Variable: The specific variable that is being measured during an experiment.
Independent Variable: The specific variable that is changed or manipulated during an experiment.
Control Variables: The variables that are kept the same throughout an experiment to ensure a fair test.

Unit of Energy: The standard unit for measuring energy is Joules ( $J$ ).
Forms of Energy: * Kinetic Energy: The form of energy possessed by a moving object. * Chemical Energy: The form of energy stored in food, fuels, and batteries. * Electrical Energy: The form of energy carried by moving electrical charges. * Light Energy: The form of energy that is visible to the eye. * Sound Energy: The form of energy emitted by vibrating objects. * Elastic Potential Energy: The form of energy stored in an object that has been stretched or compressed. * Thermal Energy: The form of energy stored by an object that depends on its temperature. * Gravitational Potential Energy: The form of energy that depends on an object's height above the surface of the Earth. * Nuclear Energy: The form of energy stored inside atoms. * Magnetic Energy: The form of energy stored inside magnets.
The Law of Conservation of Energy: Energy cannot be created or destroyed; it can only be transferred from one form into another.
Power: * Definition: Power is the rate of energy transfer, otherwise defined as the amount of energy transferred each second. * Equation: The mathematical relationship linking power, energy transferred, and time is: $\text{power} = \frac{\text{energy transferred}}{\text{time}}$

Atoms: * Definition: A particle made of protons, neutrons, and electrons. * Arrangement of Subatomic Particles: Protons and neutrons are located in the nucleus, while electrons travel around the nucleus in shells.
Arrangement of Particles by State: * Solid: Particles are close together in a regular arrangement. * Liquid: Particles are close together in a random arrangement. * Gas: Particles are far apart in a random arrangement.
Movement of Particles by State: * Solid: Particles vibrate in a fixed position. * Liquid: Particles slide over each other. * Gas: Particles move rapidly in all directions.
Density: * Definition: Density is a measure of how many particles of a substance are contained within a given volume. * Equation: The mathematical relationship for calculating density is: $\text{Density} = \frac{\text{mass}}{\text{volume}}$
Processes of Changing States: * Melting: The process of turning a solid into a liquid. * Boiling: The process of turning a liquid into a gas. * Condensing: The process of turning a gas into a liquid. * Freezing: The process of turning a liquid into a solid.
Diffusion: The movement of particles from an area of higher concentration to an area of lower concentration.
Gas Pressure: Caused by particles colliding with the sides of their container.
Effects of Heating: When a substance is heated up, the particles move faster.

Organism: A living thing.
Cell Organelles and Functions: * Nucleus: The organelle that contains DNA and controls the activities of the cell. * Cell Membrane: The organelle that controls what enters and exits the cell. * Cytoplasm: A gel-like substance where chemical reactions take place. * Mitochondria: The site of respiration, which is the process of energy release. * Ribosome: The site of protein synthesis. * Cell Wall: An organelle that strengthens and supports the cell. It also contains cell sap to keep the cell turgid (firm). * Chloroplast: The site of photosynthesis.
Cell Composition: * Animal Cell (5 Main Organelles): Nucleus, cell membrane, mitochondria, ribosome, and cytoplasm. * Plant Cell Differences: Plant cells contain a cell wall, chloroplasts, and a vacuole, which animal cells do not have.
Specialised Cells: * Animal Examples: Red blood cell, nerve cell, and muscle cell. * Plant Examples: Root hair cell and palisade cell.
Levels of Biological Organisation: * Tissue: A group of similar cells that carry out a specific function. * Organ: A group of different tissues that carry out a specific function. * Organ System: A group of different organs that carry out a specific function.

Gametes: These are sex cells. * Male Sex Cell (Human): Sperm. * Female Sex Cell (Human): Egg. * Plant Gametes: Ovule and pollen.
Sperm Cell Adaptations: The male sex cell features a tail to swim, a high concentration of mitochondria to release energy, and a nucleus containing half the genetic information.
Reproductive Anatomy: * Sperm Production: Sperm cells are made in the testes. * Egg Production: Egg cells are made in the ovaries.
The Menstrual Cycle and Fertilisation: * Control: The menstrual cycle is controlled by hormones. * Ovulation: The process of an egg being released from an ovary. * Fertilisation: This occurs when the nuclei of an egg cell and a sperm cell fuse together.
Contraception: * Types: Condoms, implants, the pill, coil, diaphragm, spermicide, injections, and sterilization. * Additional Benefit of Condoms: They provide protection against sexually transmitted diseases.
Types of Reproduction: * Sexual Reproduction: Requires two parents and involves the use of gametes. * Asexual Reproduction: Needs only one parent and does not involve gametes.