The liquid metal used in thermometers is
Important Points to Remember in Chapter -1 - Matter Around Us from Tamil Nadu Board Standard Eight Science Solutions
1. Matter
(i) Matter is defined as any substance having mass and occupies space.
(ii) Atom is the smallest particle of matter.
(iii) Molecule is the combination of two or more atoms. For example molecule.
(iv) The molecule of a substance that contains two or more atoms of different elements combined together in a definite ratio is said to be a molecule of a compound.
2. States of Matter
Matter is found in three major states: solid, liquid and gas.
(i) Solid: Material which has a definite shape and definite volume at room temperature with any number of free surfaces is called solid.
(ii) Liquid: Material which has a definite volume but no definite shape and has one free surface is called liquid.
(iii) Gases: Material which has neither definite shape nor definite volume, is easily compressible and has no free surface is called gas.
3. Symbol of Elements
Symbol: The easiest way to represent the element and to write the chemical formulas easily.
4. Metals and Non-Metals
(i) Metals are elements that are hard and shiny in appearance. Some metals used in our daily life are iron, copper, gold, silver, etc.
(ii) Metals conduct heat and electricity.
(iii) Sonority: On being hit, metals produce a typical sound. They are said to be sonorous. This property is being made used in making temple bells.
(iv) Non-metal: Elements that generally do not shine, neither too hard nor too soft are non- metals. All gases are non-metals. Some non- metals are sulphur, carbon, oxygen etc.
5. Metalloids
Elements which have some properties of metal and some of non-metals are called metalloids. Some examples are arsenic, germanium etc.
6. Compound
Compound is the substance formed by the chemical combination of two or more different elements. For example . Compounds are of two types: inorganic compounds and organic compounds.
