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Energy Change of Reactions
Some reactions take in energy and some release energy. Why? And what are some common examples of each type of reaction? Chemistry - Reactions - Learning Points. An energy change occurs when reactions take place. Exothermic reactions...
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Nitrates: Food Preservatives
Potassium nitrate is a natural substance found in your food, or in an exploding firework. What makes it so versatile? Chemistry - Chemical Industries - Learning Points. Potassium nitrate preserves our food and is a component of...
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Reactivity Series: Reactive Metals
The discovery and uses of reactive metals throughout history, and how their uses have defined the period in which they were discovered. Chemistry - Periodic Table - Learning Points. The reactivity series ranks the chemical reactivity of...
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Transition Metals
Transition metals are the largest group in the periodic table. Find out what similarities they share, and how we make use of these metals. Chemistry - Periodic Table - Learning Points. Transition metals are found as a block in the middle...
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Introduction to Chemical Bonding
The basic ways elements combine to create compounds, fundamental to life as we know it. Chemistry - Atoms And Bonding - Learning Points. There are 92 naturally occurring elements. They fall into two categories: metals and non-metals....
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Molecule
Two or more atoms held strongly together by covalent bonds. A Twig Science Glossary Film. Key scientific terms defined in just 60 seconds using stunning images and concise textual definitions. Twig Science Glossary Films reinforce...
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Distillation of Ink
We use distillation to remove the water from ink. The ink is heated in a conical flask with a delivery tube running to a beaker. The water has a lower boiling point and so it evaporates before the ink. The water condenses as it travels...
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Metal Extraction
We extract copper metal from copper chloride solution using electrolysis. The electric current causes copper to form at one electrode and chlorine gas to form at the other. The presence of chlorine is tested using blue litmus paper....
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Orange Tornado
We use mercury(II) chloride solution and potassium iodide to demonstrate a precipitation reaction. Saturated potassium iodide solution is placed on a magnetic stirrer and the speed is set so that a vortex is created. Mercury(II) chloride...
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Ionic Bonding
How metals and non-metals combine to form compounds with unique and very different properties. Chemistry - Atoms And Bonding - Learning Points. An electrically charged atom is called an ion. Ionic bonds are very strong. Ions are formed...
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Forming Iron Sulfide
We examine the different properties of iron and sulfur when they are mixed and when they are chemically combined. When iron and sulfur are mixed they retain their individual properties. When they react chemically to form iron sulfide...
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Ion Migration
We separate the ions in copper dichromate gel using electrolysis. We see the positive blue copper ions move to the negative electrode and the negative yellow chromate ions move to the positive electrode. Chemistry - Reactions - Learning...
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Extraction of Aluminium
Explore the difficulties of extracting aluminium from its ore, and how the vast quantities of heat and electricity generated by electrolysis allow this to happen. Chemistry - ReactionsLearning Points. Aluminium is difficult to extract...
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Carbohydrate
Molecules such as sugar and starch, which form an important energy source for living organisms. A Twig Science Glossary Film. Key scientific terms defined in just 60 seconds using stunning images and concise textual definitions. Twig...
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Hydroxide
Refers to the hydroxide ion, which is a negative ion consisting of an oxygen atom covalently bonded to a hydrogen atom. A Twig Science Glossary Film. Key scientific terms defined in just 60 seconds using stunning images and concise...
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Changing properties
What chemical and physical changes are at play in cake baking. Material processes - Changing materials - More chemical reactions Learning Points Chemical changes are usually irreversible. Physical changes are usually reversible. Chemical...
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Biphenyls & Optical Isomerism: When Planes Matter
Biphenyls are compounds consisting of two benzene rings connected by a single bond. In certain biphenyls, bulky substituents on the ortho positions of the rings can prevent free rotation around the bond, locking the rings in different...
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Allenes and Optical Activity: A Surprising Twist!
Allenes are compounds with a unique structure characterized by two adjacent double bonds (C=C=C). Despite having no traditional chiral centers, certain substituted allenes can exhibit chirality and optical activity due to their rigid,...
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Lactic Acid: A Case Study in Chirality
Lactic acid (2-hydroxypropanoic acid) is a classic example of a chiral molecule. It contains a chiral center at the second carbon atom, bonded to a hydroxyl group (-OH), a hydrogen atom, a carboxyl group (-COOH), and a methyl group...
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Symmetry and Optical Activity: Do Your Molecules Have It?
Symmetry and optical activity are intricately linked in organic molecules. A molecule is optically active if it can rotate the plane of polarized light. Optical activity arises from the molecule’s lack of symmetry—specifically, its...
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Conditions for Optical Activity: When Molecules Twist Light
For a molecule to exhibit optical activity, it must be chiral, meaning it has no internal plane of symmetry. Additionally, the solution or compound should not contain equal amounts of enantiomers (racemic mixture), as these cancel out...
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Specific Rotation: Measuring Optical Activity
Specific rotation is a standardized measure of how much a chiral compound rotates plane-polarized light. It's dependent on the substance’s concentration, the path length of the light, and the temperature, providing key insights into a...
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Optical Activity: When Light Meets Molecules
Optical activity refers to the ability of chiral compounds to rotate the plane of polarized light. Compounds that rotate light clockwise are termed dextrorotatory (+), while those that rotate it counterclockwise are levorotatory (−). The...
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Functional Isomerism & Metamerism: Discovering Molecular Twins
Functional isomerism occurs when compounds with the same molecular formula have different functional groups. For instance, ethanol (an alcohol) and dimethyl ether (an ether) share the formula 𝐶2𝐻6𝑂C2H6O but differ in their functional...