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exploring diversity of matter by chemical composition (what are elements?…
exploring diversity of matter by chemical composition
pg 64 for learning outcomes and questions and mystery
there are millions of substances in world. in order to make sense of this diversity, we need to classify them
pure substances and mixtures
salt is pure substance while solution of salt in water is mixture
pure substances can be further classified into 2 groups: elements and compounds
elements: gold and iron
compounds: salt and sugar
what are elements?
in daily life, often make objects by joining basic building blocks together
matter is similar to this
there are millions of substances in world but they are all made of small number of building blocks called elements
all matter is made of it
building blocks of all living ang non living things
an element is pure substance that cannot be broken down into any simpler substance by chemical methods
112 named and found elements, 92 found on earth, 20 made artificially
pg 66 and 67
can be classified as solids, liquids and gases
found everywhere
how are elements represented?
each element is represented by symbol. for many elements, symbol is first one or two letters of name of element. first letter is always captial letter, while second letter is small letter
pg 68
international science
symbols for elements are unique
no 2 elements have same symbol
using standard symbols ensure there is no confusion when refer to particular element
how can we classify elements?
there are more than 100 elements
classifying elements by state
solids, liquids and gases
11 elements are gases
2 elements are liquids:mercury, bromine
all other elements are solids
classifying elements as metals and non metals
most elements are metals
all metals, except mercury, are solid at room temperature
non metals may be solids, liquids or gases at room temperature: carbon(solid), bromine (liquid) and chlorine (gas)
metals and non metals have their own set of properties
pg 70
classifying elements as in periodic table
arranged in periodic table based on properties
elements made up of tiny particles called atoms
each atom is described by number called proton number
in periodic table, elements are arranged by proton numbers of respective atoms
elements are then classifies into groups. elements in SAME GROUP HAS SIMILAR PROPERTIES