matter is anything that occupies space and has mass.
Matter exist in three states namely:
1.Solids: rigid objects with definite shape. Examples are, rock, salt, chalk, plastic, cotton, etc.
2.Liquids: objects that flows and have no definite shape but assume the shape of the container in which it is held. Examples are water (H2O), ethanol, oil, etc.
3.Gas: substance such as air. Thus, a substance that is neither a solid nor a liquid at ordinary temperatures and has the ability to expand indefinitely. Example, ammonia (NH3), carbon dioxide (CO2), nitrogen gas (N2), etc.
However, Plasma is the fourth state emerging. Plasma is an ionized gas.
These three sates of mater can interconvert. Thus, they can be changed from one state to another.
Upon heating, a solid will melt and become liquid. Further heating will convert the liquid into a gas.
On the other hand, cooling a gas will condense it into a liquid, further cooling will convert the liquid into a solid.
Classification of Matter:
•Based on composition and properties, matter can be classified into;
- Substances
- Mixtures
- Elements and
- compounds
Substances and Mixtures
•Substances:
- A substance is matter that has a specific composition and specific properties. Substances can either be a solid, powder, liquid or gas. Example, water, silver, ethanol, table salt, carbon dioxide, etc.
- Thus, they differ from one another in composition and can be identified by their appearance, smell, taste, touch, and other properties.
- A substance can either be an element or compound but NOT a mixture.
Mixtures:
- A mixture is a physical (with no chemical reaction) combination of two or more substances in which the substances retain their individual properties.
- Examples are air (oxygen + hydrogen + nitrogen + carbon dioxide + other gasses), mortar (sand + water + cement), ocean water (water + salt), etc.
- Mixtures do not have definite composition. Therefore, samples of mortar collected at different constructions sites would have different proportions of sand, water and cement.
- Mixtures can either be classified as homogeneous or heterogeneous.
Homogeneous Mixture:
- homogeneous (Latin homo, meaning “same”) mixture is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture.
- Example, when a spoonful of sugar is dissolved in water, the composition of the mixture, after sufficient stirring, is the same throughout.
- A homogeneous mixture of two or more substances is called a solution.
Heterogeneous Mixture:
- A heterogeneous (Greek hetero, meaning “other”) mixture is a mixture that does not have a uniform distribution and properties throughout.
- Example is a mixture of sand and iron fillings OR oil and water.
•Any mixture, whether homogeneous or heterogeneous, can be created and then separated by physical means into pure components without changing the identities of the components.
•Thus, salt can be recovered from a water solution by heating the solution and evaporating it to dryness. Condensing the water vapor will give back the water component.
Normal Saline (Salt in water)= homogenous mixture Amoxicillin Suspension= heterogenous mixture
Elements and Compounds:
Elements:
- An element is a substance that cannot be separated into simpler substances by chemical means.
- Thus, An element is any substance that contain only one kind of substance.
- Example, water (H2O) decomposes into a mixture of hydrogen and oxygen gasses when an electric current is passed through it. Hydrogen (H) and oxygen (O), on the other hand, cannot be decomposed into other simpler substances.
- They are therefore the elementary, or simplest chemical substances of water.
- Hydrogen and oxygen are thus called elements.
- Sodium Element
- Carbon Element
- Gold Element
- Copper Element
- Phosphorus Element
- Lithium Element
- At present, 118 elements have been positively identified. 92 of them occur naturally and the 26 others were created by scientist through the processes of radioactivity.
- Each element is represented by a unique alphabetical symbol. The first letter of the symbol for an element is always capitalized, but the second letter is always lower cased.
- Examples are Iron (Fe), Aluminum (Al). Gold (Au), Platinum (Pt), Silver (Ag), Oxygen (O), Calcium (Ca), Sodium (Na), etc.
- lthough most of them are abbreviated forms of their English names, example, Calcium (Ca), Aluminum (Al), Platinum (Pt), etc., some of them are derived from their Latin names, example, Au from aurum (Gold), Fe from ferrum (Iron), and Na from natrium (Sodium).
- A tabular array or all existing elements in order of increasing atomic number is called the periodic table.
- These elements can be divided into three categories with characteristic properties:
1.Metal: usually a solid element at room temperature that is malleable, ductile, has a characteristic luster and is a good conductor of heat and electricity, e.g. gold, iron, copper, aluminum, zinc, etc. They are found on the left and toward the bottom of the periodic table.
•Malleable refers to that which can be bent or shaped without breaking.
•Ductile refers to that able to be drawn out into wire or hammered into very thin sheets.
•Luster refers to that having brightness or shiny surface.
•Nonmetal: a solid, liquid or gaseous element that does not display the properties of a metal, e.g. oxygen (O), carbon (C), nitrogen (N), sulphur (S), iodine (I), etc. They are found on the upper right corner of the periodic table.
•Semimetal or metalloid: a solid element with properties intermediate between metals and nonmetals, e.g. boron (B), silicon (Si), arsenic (As), etc. They are found along the diving line between the metals and the nonmetals.
•Compounds:
most elements can interact with one or more other elements to form a single substance called a compound.
Thus, a compound is a substance composed of two or more elements chemically joined together in a fixed proportion.
A compound can also be defined as the chemical combination of two or more atoms from two or more different elements.
Compounds have properties very different from the properties of their individual elements.
example pure water is a compound made from two atoms of hydrogen (2H) and one atom of oxygen (1O).These atoms were obtained from a hydrogen and oxygen elements. The ratio of hydrogen to oxygen is always 2:1 and does not change, regardless of whether the water comes from Ghana or Nigeria, from a river, sea, or lake.
Table salt or sodium chloride is a compound made from sodium and chlorine element. Thus, the ratio of sodium to chlorine is always 1:1
Pure glucose(C₆H₁₂O₆) is made from three elements – carbon, hydrogen, and oxygen. The ratio of hydrogen to carbon and oxygen in glucose is always 2:1:1.
the force of attraction holding atoms together in a molecule is called a bond or chemical bond.
The process through which two or more substances or atoms combine to form a molecules is called a chemical reaction.
A chemical formula is a shorthand notation or symbols used to describe the composition of each element in a compound. The element is represented by its symbol and the quantity of that element in the compound is indicated by a subscript following the element’s symbol.
No subscript is written when a molecule contains only one atom of an element.
Example, there are 2 H (hydrogen) elements and 1 O (oxygen) element in water, and hence have a chemical formula H2O
Glucose has 12 H (hydrogen) elements, 6 C (carbon) elements and 6 O (oxygen) elements and hence represented as C6H12O6.
The two or more substances or atoms undergoing a chemical reaction are called reactants.
The substance formed from a chemical reaction of two or more substances or atoms is called the product.
Atomic Components or Structure
•Atom is the smallest particle of an element that can retain the ordinary properties of that element. Examples of atoms include, Hydrogen, Neon, etc.
•The Structure of the atom
- An atom consists of a tiny dense nucleus surrounded by electrons that are spread throughout a relatively large volume of space around the nucleus.
- The nucleus contains positively charged protons and neutral neutrons, so it is positively charged.
- Electrons are negatively charged and move around the nucleus in orbits.
- Protons and neutrons have approximately the same mass and are about 1800 times more massive than an electron.
It is electrons that form chemical bonds and of interest to the chemist.
The structure of the atom
•Atomic Number (Z), Mass Number (A) and Isotopes:
All atoms can be identified by the number of protons and neutrons they contain.
The number of protons in the nucleus of each atom of an element is called the atomic number, represented by Z.
A neutral atom has an equal number of positively charged protons and negatively charged electrons, so the atomic number (Z) also indicates the number of electrons present in an atom.
The chemical identity of an atom is determined solely by its atomic number. Example, Nitrogen has an atomic number of 7, meaning, every atom in the universe that contains 7 protons is correctly named “nitrogen”.
•The mass number (A) is the total number of protons (Z) and neutrons (n)present in the nucleus of an atom of an element.
•Mathematically expressed as:
A = Z + n
Mass number = Number of protons + number of neutrons
•Except for hydrogen which has 1 proton and no neutron represented as H11, all other atomic nuclei contain both protons and neutrons.
•Chemical symbols of the elements in the periodic table provide information about their atomic numbers and mass numbers.
•The proton number (Z) is shown below the chemical symbol and the mass number (A) is shown above as shown below:
Z + n
Z
Example, for 5729Co, the mass number (A) is 57 and the proton number (Z) is 29.
- From A = Z + n, we can simply say that the number of neutrons, n = A – Z.
- Hence, for 5729Co, number of neutrons, n = 57 – 29 = 28.
- Thus, for the above compound, 5729Co, Mass number (A) = 57,
- Number of protons (Z) = 29
- Number of neutrons (n) = 28
- Number of electrons = 29