Matter

1. Matter can be defined as anything, which occupies space or volume and mass and can be perceived by our senses.

2. Matter exists in three states:

◦ Solids:

Substances like wood, stone, sand, iron etc.

◦ Liquids:

Substances like water, milk, fruit juice, etc.

◦ Gases:

Substances like oxygen, nitrogen, carbon dioxide, steam, etc.

3. Matter in any physical state is composed of smaller particles such as atom, molecules or ions.

◦ Atom:

An atom is the smallest particle of an element, which exhibits all the properties of that element. It may or may not exist independently but takes part in every chemical reaction.

◦ Molecules:

Atoms of the same element or different elements combine to form a molecule. A molecule is the smallest particle of a pure substance (element or compound), which can exist independently and retain the physical and chemical properties of the substance.

◦ Ions:

Atoms or group of atoms having a charge (positive or negative) are called ions.

4. A symbol is an image, object, etc., that stands for some meaning.

5. History of symbols of elements

◦ Greek symbols:

The symbols in form of the geometrical shapes were those used by the ancient Greeks to represent the four basic elements around us such as earth, air, fire and water.

◦ Alchemist symbol:

In the days of alchemists, the different materials that they used were represented by the above-mentioned symbols while they try to change less valuable metal into gold. The process was called alchemy and the men who did this work were known as alchemists.

◦ Dalton symbols:

In 1808, John Dalton, English scientist tried to name the various elements based on these pictorial symbols. These symbols are difficult to draw and hence they are not used today.

◦ Berzelius symbols:

In 1813, Jon Jakob Berzelius devised a system using letters of alphabet rather than signs.

6. Present System for Determining Symbols of the Elements

◦ The symbols of the most common elements, mainly non-metals, use the first letter of their English name. It is written as a capital letter.

◦ If the name of the element has the same initial letter as another element, then symbol uses the first and second letters of their Element name. First letter in upper case and the second letter is in lower case.

◦ If the first two letters of the names of elements are the same, then the symbol consists of first letter and second or third letter of English name that they do not have in common.

◦ Some symbols are used on the basis of their old names or Latin name of an element.

◦ Some elements are named using name of country/scientist/color/mythological character/planet.

7. A symbol of an element signifies

◦ Name of the element

◦ One atom of the element For example, The symbol O stands for the element of Oxygen, or rather one atom of oxygen

8. The wealth of a country is measured by the amount of gold in its reserve.

9. Elements are classified into metals, non-metals, and metalloids based on their properties

10. Physical Properties of Metal:

◦ Physical state:

Metals are solid under normal conditions of temperature and pressure.

◦ Exception: Mercury is liquid at room temperature. Elements cesium (Cs), rubidium (Rb), Francium (Fr) and Gallium (Ga) become liquid at or just above room temperature.

◦ Hardness: Most metals are hard.

◦ Exception: Sodium and potassium are soft enough to be cut by a knife. Osmium is so hard that it can scratch glass.

◦ Luster: All metals are shiny. The typical shine of metals is called metallic lustre.

◦ Exception is calcium.

◦ Density: Metals generally have high density.

◦ Exception: Sodium and potassium have exceptionally low density.

◦ Melting point and boiling point: Metals in general have high melting point and boiling point. Exception: Sodium, potassium, mercury and gallium are exceptions.

◦ Tensile strength: Metals have the capacity to withstand strain without breaking. This property is called tensile strength.

◦ Use: It is the property that owes the use of iron for the construction of railway tracks.

◦ Exceptions: Zinc, arsenic and antimony have low tensile strength.

◦ Malleability: Metals can be hammered into very thin sheets. This tendency of metals is called malleability.

◦ Use: Aluminum makes use of this property to transform into silvery foils.

◦ Ductility: Metals can be drawn into thin wires. This property of metals is called ductility.

◦ Use: copper wires.

◦ Conductivity: Metals are good conductors of heat and electricity. Silver and copper are very good conductors of electricity.

◦ Exception: Bismuth and tungsten are poor conductors.

◦ Sonorous: On being hit, metals produce a typical sound. Hence, they are said to be sonorous.

◦ Use: This property is being made used in making temple bells.

11. Physical Properties Of Non-Metals

◦ Physical state:

Non-metals occur as solids, liquids or gases at normal temperature.

◦ For example sulphur, phosphorus occurs in solid state while bromine occurs in liquid state. Gases like oxygen, nitrogen, etc., occur in the gaseous state.

◦ Hardness:

Non-metals are generally not hard.

◦ Exception:

Diamond (it is a form of carbon)

◦ Luster:

Non-metals have a dull appearance.

◦ Exception:

Graphite and iodine are exceptions as they are shiny and lustrous.

◦ Density:

Non-Metals are generally soft and have low densities.

◦ Exception:

Diamond is the hardest naturally occurring substance.

◦ Melting point and boiling point:

Non-metals have low melting point and boiling point.

◦ Exceptions: carbon

◦ Tensile strength:

Non-metals do not have tensile strength.

◦ Exception:

Carbon fibre (a form of carbon) is as tensile as steel.

◦ Malleability:

Non-metals are non-malleable. If hammered, they form a powdery mass. That is, non-metals in solid state are brittle in nature.

◦ Ductility:

Non-metals are not ductile.

◦ Exception:

Carbon fibre is highly ductile.

◦ Conductivity:

Non-Metals are generally bad conductor of electricity.

◦ Exception:

Graphite

◦ Sonorous:

Non-Metals do not produce sound (non-sonorous) when hit.

12. Uses of Metal

◦ Iron is used for making bridges, engine parts, iron-sheet and bars.

◦ Copper is used for making electrical wires, coins and statue.

◦ Silver and gold are used for making jewels, in decorative purposes and photography.

◦ Mercury is used in thermometers and barometers because of its high density and uniform expansion at different temperature.

◦ Aluminium is used in electrical wires, cables and in aerospace industries.

◦ Lead is used in automobile batteries, X-ray machines.

13. Uses of Non-Metals

◦ Diamond (a form of carbon) is used for making jewels, cutting and grinding equipment.

◦ Graphite is used in making pencil lead.

◦ Sulfur is used in the manufacturing of gun powder and vulcanization of rubber.

◦ Phosphorus is used in matches, rat poison etc.

◦ Nitrogen is used for manufacturing ammonia.

◦ Chlorine is used as a bleaching agent and in sterilizing water.

◦ Hydrogen is used as a rocket fuel and hydrogen flame is used for cutting and welding purposes, as well as a reducing agent

14. The elements which exhibit the properties of metals as well as non-metals are called metalloids. Examples: boron, silicon, arsenic, germanium, antimony, tellurium and polonium.

15. Physical properties of metalloids

· Metalloids are all solid at room temperature.

· They can form alloys with other metals

· Some metalloids, such as silicon and germanium, can act as electrical conductors under the specific conditions, thus they are called semiconductors.

· Silicon for example appears lustrous, but is not malleable nor ductile (it is brittle - a characteristic of some non metals). It is a much poorer conductor of heat and electricity than the metals

· The physical properties of metalloids tend to be metallic, but their chemical properties tend to be non-metallic.

16. Uses of metalloids

◦ Silicon is used in electronic devices.

◦ Boron is used in fireworks and as a fuel for ignition in rocket.

17. A compound is a pure substance which is formed due to the chemical combination of two or more elements in a fixed ratio by mass.

18. The properties of a compound are different from those of its constituents.

19. Classification compound based on the origin of chemical constituents, compounds are classified as inorganic compounds and organic compounds.

◦ Inorganic compounds Compounds obtained from nonliving sources such as rock, minerals etc., are called inorganic compounds. Example: chalk, baking powder etc.,

◦ Organic compounds Compounds obtained from living sources such as plants, animals etc., are called organic compound. Example: Protein, carbohydrates, etc.

20. Both inorganic and organic compounds exists in all three states of matter I.e., solids, liquids and gases.

21. Examples of compounds in solids state

22. Examples of compounds in liquids state

23. Examples of compounds in gaseous state

24. Some useful compounds