Year 8 Science Full Year Content Notes PDF

Year 8 Science Full Year Content Notes Cells and Specialised Cell Structures -\> **Cells:** A cell is the smallest unit of a living thing. A living thing, whether made of one cell or many cells is called an organism. Thus, cells are the basic building blocks of all organisms. **Cell theory:** 1....

Year 8 Science Full Year Content Notes Cells and Specialised Cell Structures -\> **Cells:** A cell is the smallest unit of a living thing. A living thing, whether made of one cell or many cells is called an organism. Thus, cells are the basic building blocks of all organisms. **Cell theory:** 1. All living things are made up of one or more cells. 2. The cell is the most basic building block of living things. 3. All cells are made from pre-existing cells. Nucleus: Stores genetic information Mitochondria: Powerhouse of the cell Endoplasmic Reticulum: Transports proteins inside the cell Golgi Apparatus: Sorts and ships proteins outside the cell Ribosomes: Makes proteins Cell Wall: Provides structure, support and protection (acts as a barrier) Chloroplast: Converts sunlight into energy through photosynthesis Vacuole: Stores water, nutrients and waste. **Mitosis:** (memorise it by IPMAT) I: Interphase P: Prophase M: Metaphase A: Anaphase T: Telophase Organ Systems -\> **Unicellular organisms:** Organisms that consist of one cell only! This means that all their life processes, such as reproduction, feeding, digestion, and excretion, occur in one cell. Examples: include pond water organisms such as *Amoeba* and *Paramecium*. **Multicellular organisms:** A tissue, organ or organism that is made up of many cells. Examples: Humans, animals and plants are all examples of multicellular organisms.   The Respiratory System: The Circulatory System:  **Digestion:** Digestion is how our body breaks food into tiny pieces that it can use for energy and growth. It starts in the mouth when we chew, then in the stomach, where juices break down the food even more. Finally, in the small intestine, nutrients are absorbed into the blood to be used by the body. **Gas Exchange at the Alveoli:** In the lungs, we have tiny air sacs called alveoli. When we breathe in, oxygen goes into these sacs and moves into our blood. At the same time, carbon dioxide (a waste gas) leaves the blood and goes into the alveoli so we can breathe it out. **Role of the Kidneys in Excretion:** The kidneys clean our blood by removing waste like urea and extra water, which turn into urine. They also help keep the right balance of water and salts in the body and control things like blood pressure. Reproduction -\> Asexual Reproduction: In asexual reproduction, there is no joining of egg and sperm. Instead, the young grows from part of the parent's body or from an unfertilised egg. The individual is produced by mitosis, the process in which a cell splits into two identical cells. Most species of animals reproduce sexually, with only a few species reproducing asexually. Examples include budding, fission, parthenogenesis. Sexual Reproduction: Sexual reproduction happens when a sperm from a male enters an egg from a female and fertilises it. The process is called fertilisation. Sperm and eggs are special reproductive cells, known as gametes. The male gamete is sperm, and the female gamete is the egg. Fertilisation results in a new cell called a zygote. The zygote then grows by dividing to form many copies of itself. The zygote eventually grows and develops into a new individual.  The human reproductive system helps develop and maintain female sex characteristics and play an important role in fertility, pregnancy, and the menstrual cycle. Male reproductive hormones, such as testosterone, help develop and maintain male sex characteristics and help make sperm in the testes. Matter -\> **Elements**: Substances made up of only one type of atom. They cannot be broken down into simpler substances by chemical means. (H, O, Fe). **Compounds**: Substances made from two or more elements that are chemically bonded together. The elements in a compound are always present in fixed ratios (H₂O, CO₂). **Mixtures**: Physically combined substances (air, saltwater).  Physical and Chemical Changes-\> **Physical changes:** involve no new substances and are often reversible. **Chemical changes:** produce new substances and are usually irreversible. **Chemical reactions:** are indicated by colour changes, gas formation, temperature changes, **Energy changes:** in reactions can either release heat (exothermic) or absorb heat (endothermic).  Physics -\> **Energy formulas:** **Gravitational Potential energy (GPE)** = mgh - m = mass (in kg) - G = gravitational acceleration (9.8 m/s squared) - H = height **Kinetic energy (KE)** = 0.5 × m × v squared - m = mass (kg) - v = velocity (m/s) (The faster and bigger it is, the more KE there is). **Energy =** Power × Time - Power in watts (W) - Time in seconds (s) **Electrical power** = V x I - V -- Voltage in volts - I -- current in milliamps **Ohms Law:** V=IR V - Voltage -- Volts (v). Force driving the flow of electrons. R - Resistance -- Ohms. Everything that resists or opposes the flow of electrons. I - Current -- I (amps). A measure of the flow of electrons around the circuit. IMPORTANT: Velocity is measured in meters per second (m/s), not m/s². The unit m/s² is for acceleration (such as gravitational acceleration, g). 1 Kilojoule = 1000 joules 1 megajoules = 1 000 000 joule (or 1000 kj) **The following Sankey diagram shows the energy flow in a light bulb:** **Conduction, convection, and radiation:** Conduction -- objects that are in touch. Convection -- travelling through liquid or air. Radiation -- Moving as waves or particles. Cool objects in warm places take in energy, and warm objects lose energy to cooler energy. There is no loss of energy when a potential store of energy becomes another kind. **Circuits:** Series circuit -- a circuit that only has one path for the energy to flow. Parallel circuit -- a circuit that has multiple paths for the energy to flow.  **Resistance:** Higher resistance is harder for electrons to pass through. Lower resistance is easier. Type of resistance of a wire depends on: What is it made of? What is the length of the wire? What is the thickness of the wire?