ChemistryWhat is it? Molecule Structure Periodic Table
What is Chemistry?Chemistry is a branch of physical science, itis the study of the composition, propertiesand behaviour of matter. Chemistry is aboutatoms and their interactions with otheratoms, and particularly with the propertiesof chemical bonds. Chemistry is also aboutthe interactions between atoms (or groupsof atoms) and various forms of energy.
The PeriodicTableA periodic table is a rectangular display of the elements, organized on the basis of their: Atomic numbers Electron configurations Recurring chemical propertiesElements are presented in order of increasing atomic number.
What is pH?Two of the most important groups of chemicals arethe ‘acids’ and the ‘bases’.Acids are solutions containing hydrogen (H+) ions.Bases are solutions that contain metal oxide ions.Alkalies are solutions that contain hydoxide ionsand carbonate ions.An ion is an atom that has either gained or lost oneor more electrons.The strength of acids and bases is measured usinga scale called pH. This stands for ‘postivehydrogen ion concentration’.It is a scale of around 0 to 14. Strong acids have alow pH and strong alkalies have a high pH.Pure water has a pH of 7, this is neutral. In this diagram, it shows a baseThe Acid in our stomachs is about 2, and so strong (blue-pH 10) being added to anthat it is able to ‘burn away’ rocks like limestone acid (yellow-pH 5/6), andand chalk. neutralising it (becoming green- pH 7)
There are 6 elementsthat make up 99% of your body Oxygen 65% massCalcium 1.5% mass 25.6% atoms 0.25% atomsCarbon 18% mass Hydrogen 10% mass 9.5 % atoms 63% atomsPhosphorous 1.0% mass Nitrogen 3% mass 0.20% atoms 1.35% atoms
Cooking is aChemical ReactionA chemical reactionhappens when bondsbetween atoms andmolecules are made orbroken. We often melt orfreeze food in cooking, butthis is a reversible reaction.It would be difficult to unmixdough or cake mix, but nochemical change occursuntil the heat from an oventouches the dough or food.
Scientists can turn Lead into GoldScientist have beenable to turn lead intogold. The nucleus oflead has 82 protonswhile the nucleus ofgold has 72 protons.They turn lead intogold by taking off 3protons.They used anuclear reactor.
A Cubic metre of sea water contains over 12 kilograms of Metal.Sea water contains minute The oceans containamounts of most metals. about 0.000,004 gWhen rain water first falls to of gold per cubicthe ground it doesn’t contain metre. This may notany salts. However, as this sound like a lot, butwater seeps through the when we think aboutground, it dissolves rocks how large thelike limestone and chalk. As oceans are, that isa result, rainwater will about 5.5 millioncontain dissolved mineral tonnes of gold.salts when it flows into thesea or it reaches our hometap water.
A Rubber Molecule Can Stretch to over FourTimes its Natural LenghtRubber is a biological moleculemade naturally by rubber trees.A single rubber molecule is a long,thin chain composed of hundredsof thousands of atoms. Themolecules in a rubber band areloosely tangled a round each otherin other in loops and coils. Whenyou pull on a rubber band, themolecules straighten out so that theband can become longer. Once themolecules are straight the rubberbecomes very stiff.