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Glossaryacid - a substance is an acid or is acidic if it has pH less than 7. Acidic substances turn universal indicator red, orange or yellow. algae - a very simple type of plant, that lives in water, or on moist ground. calcium carbonate - the chemical name for limestone. Its formula is CaCO3. All carbonates are insoluble in water. Calcium carbonate is one of the minerals responsible for hard water. carbon dioxide - a compound made up of one atom of carbon and 2 atoms of oxygen. Its formula is CO2. Carbon dioxide is a non metal oxide and is acidic. It is present in tiny amounts in the atmosphere, less than 0.035%. When plants and animals respire they give out CO2. Carbon dioxide is also added to the atmosphere when fossil fuels, like petrol, are burnt. Plants remove carbon dioxide when they make their own food, by the process of photosynthesis. Carbon dioxide is also removed when it dissolves in water to produce insoluble carbonates and soluble hydrogen carbonate ions. condensation - the physical change in which a cooled gas turns into a liquid. compound - a substance in which two or more elements are chemically combined. eutrophication - what happens to lakes and rivers if too much nitrate gets into the water. Nitrates are from fertilisers. The nitrates encourage algae to grow. This cuts out light to water plants that live below the surface. Without light, the plants die and rot away. This removes all the oxygen in the water and all life in the water dies! evaporation - the physical change during which a liquid turns to a gas at a temperature below the boiling point. fertiliser - a chemical that provides the necessary nutrients for plants to grow. filtrate - the clear liquid obtained during filtration. This is the liquid that comes through the filter funnel. gypsum - a mineral found in rocks. Its chemical formula is CaSO4.2H2O, calcium sulphate. hard water - Water that contains calcium and magnesium ions. This type of water will not form a stable lather with soap. insoluble - describes a chemical that does not dissolve in a solvent. limestone - the common name for calcium carbonate. Limestone is a sedimentary rock. precipitation - all liquid and solid forms of water that fall from the atmosphere. precipitate - an insoluble chemical produced during a chemical reaction. soft water - water which contains more sodium ions than hard water. Soft water makes soaps form a lather (bubbles) better than hard water. Soft water does not make your kettle fur up. soluble - describes a solid chemical (e.g., salt) that dissolves in a solvent. solvent - the liquid (e.g., water) in which a solute dissolves to make a solution. suspension - a suspsension is when very small particles of a solid are suspended, or held, in a liquid. They don't settle to the bottom of the liquid, but instead are spread all around it. thermal decomposition - using heat to break a compound down into something simpler.
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