Chemical Chaos
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Combustion Reactions: Combustion happens when a substance reacts with oxygen and releases energy. Hydrocarbons usually produce carbon dioxide and water. Example: methane + oxygen → carbon dioxide + water. Burning petrol, wood, and candles are combustion reactions.
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Exothermic vs Endothermic: Exothermic reactions release heat and make surroundings warmer. Combustion and respiration are exothermic. Endothermic reactions absorb heat and make surroundings cooler. Photosynthesis is an endothermic reaction.
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Corrosion: Corrosion is the slow destruction of metals through chemical reactions. Rusting occurs when iron reacts with oxygen and water. Salt water, moisture, and heat speed up corrosion. Paint and galvanising help prevent corrosion.
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Precipitation Reactions: A precipitation reaction forms a solid called a precipitate when two solutions mix. The precipitate is insoluble in water. Cloudiness or solid particles show a precipitate has formed. Example: silver nitrate + sodium chloride forms silver chloride.
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Solubility Rules: Most sodium salts and nitrates dissolve in water. Silver chloride and barium sulfate are insoluble and form precipitates. If a product is insoluble, a precipitate forms. Solubility rules help predict reactions.
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Reaction Rate Factors: Higher temperature increases particle movement and reaction speed. Greater concentration causes more collisions between particles. Larger surface area exposes more particles to react. Catalysts speed up reactions without being used up.
The Blueprint of Life
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Mutations: Mutations are changes in the DNA sequence. They can involve missing, added, or changed bases. Mutations may be harmful, helpful, or have no effect. Some mutations cause genetic disorders.
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Causes and Effects of Mutations: Mutations can happen naturally during DNA copying. UV radiation, chemicals, and smoking can damage DNA. Mutations may change protein production. Some can lead to diseases such as cancer.
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Genes, Chromosomes, and DNA: DNA carries genetic instructions. Genes are sections of DNA that code for traits. Chromosomes are long strands of DNA found in the nucleus. Humans normally have 46 chromosomes.
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Transfer of Genetic Information: Genetic information is stored in genes on chromosomes. DNA passes information from parents to offspring. Genes determine characteristics such as eye colour. Cells use genes to make proteins.
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Levels of Organisation: Cells are the basic unit of life. Similar cells form tissues. Tissues form organs, and organs form organ systems. Organ systems work together in an organism.
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Karyotype Analysis: A karyotype is an image of chromosomes arranged in pairs. Scientists use it to check chromosome number and structure. It can identify conditions such as Down syndrome. Humans usually have 23 chromosome pairs.
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DNA and Proteins: DNA contains instructions for making proteins. Proteins control body functions and build structures like muscles. The order of DNA bases determines protein structure. Without proteins, cells cannot function properly.
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History of DNA Discovery: Gregor Mendel studied inheritance using pea plants. Rosalind Franklin captured X-ray images of DNA. Watson and Crick used this information to describe the double helix. Their work explained how DNA stores information.
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Structure and Function of DNA: DNA has a double helix shape like a twisted ladder. It is made of sugar, phosphate, and nitrogen bases. Bases pair specifically: A with T, and C with G. This structure allows accurate storage of genetic information.
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DNA Replication: DNA replication copies DNA before cell division. The strands unzip and matching bases are added. This ensures new cells receive identical DNA. Replication is important for growth and repair.
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Asexual and Sexual Reproduction: Asexual reproduction involves one parent and produces identical offspring. Sexual reproduction involves two parents and creates variation. Mitosis is used in asexual reproduction. Meiosis produces sex cells for sexual reproduction.