Provide consistency in the collection and use of data across multiple members of a research team.Help define conventions that are to be used across a project.Assist in avoiding data inconsistencies across a project.Why Use a Data Dictionary?ĭata Dictionaries are useful for a number of reasons. The metadata included in a Data Dictionary can assist in defining the scope and characteristics of data elements, as well the rules for their usage and application. A Data Dictionary also provides metadata about data elements. It describes the meanings and purposes of data elements within the context of a project, and provides guidance on interpretation, accepted meanings and representation. Presenter: So all of these molecules together make water, which is a compound.A Data Dictionary is a collection of names, definitions, and attributes about data elements that are being used or captured in a database, information system, or part of a research project. And then the two white circles, they represent the two hydrogen atoms that are chemically bonded together. These little red blobs represent the oxygen atoms. So, a molecule is a word we use to represent the simplest unit of some compounds. The chemical name for water is H₂O because each of its molecules contain two hydrogen atoms and one oxygen atom. Water is a compound of hydrogen and oxygen. We're surrounded by lots and lots of different compounds all of the time. OK, so, can you give us some examples of compounds? Could I find some at home? So, two or more elements that chemically bond together will form a compound. And then can we mix different atoms together? Teacher: But a piece of pure gold will contain only gold atoms, whereas a piece of pure lead will contain only lead atoms. For example, we've got lead and we've got gold. So, different elements are made of different atoms. Teacher: No, elements are made of only one type of atom.
Are elements made up of a mixture of different types of atoms? Presenter: OK, let's make sense of all this with Mrs Roberts. Particle diagrams can also show the ratio of atoms of each element in a compound which in turn can tell us the formula of the compound - H₂O. In one molecule of water, there are two hydrogen atoms and one oxygen atom. This particle diagram represents water or, to use its chemical formula, H₂O which is a compound of the elements hydrogen and oxygen. See how they're represented by two circles of different size and colour that are joined together. These clusters of strongly bonded atoms are called molecules. When atoms of two or more elements bond together, they make a compound. In a particle diagram, atoms are represented by a single coloured circle. Well, before we get into this further, let's check out the top things to know about all of this.Īn atom is the simplest particle of an element. There are over one hundred different elements and these are all made of atoms. So now an atom is the smallest particle of an element. Now, to make the diagrams simpler we often just draw them as circles. Teacher: Well, we usually imagine atoms to be like tiny balls like this. Well, is there a way to help us visualise atoms to help us learn about them? So if people were the size of an atom, the entire population of the world would fit into a box about 1000th of a millimetre across. Teacher: Well, atoms are the tiny particles that are too small to see, even with a microscope. Just these handsomely, devilish good looks. Presenter: It's funny, because I don't remember seeing any atoms last time I looked in the mirror. Grit, determination, hardworking, handsome, charming, funny. Teacher: What do you think you're made of?īig question.
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