Classwork Series and Exercises {Chemistry- SS1}: Nature of Matter

What is Matter?

Matter is anything that has mass and occupies space. There are 3 states of matter, solids, liquids and gases. Examples of matter include the plants animals around us, the food we eat, the water we drink and even the air we breathe. In general, matter is built up of one or more of the following elementary particles: atoms, molecules and ions.

Properties of Matter

Substances can be identified using the characteristics possessed by the substance. These characteristics are called properties. The properties may be physical or chemical.

• Physical properties are properties associated with physical changes. Common physical changes of a substance include its boiling point, melting point, density, hardness, malleability, crystalline form, as well as properties which may be detected by the senses such as colour, odour, and taste.
• Chemical properties are those properties which are involved when matter undergoes a change to form new substances. The rusting of iron is a chemical property of iron since a new substance, iron rust, is formed.

Physical and Chemical changes

Matter undergo two types of change

Physical Change: This is a change which is easily reversed and in which no new substance is formed.

Examples of physical change include:

• The dissolution of common salt in water.
• Changes in the states of matter such as the melting of solids to liquids, the freezing of liquid to solids, the vaporization of liquids to gases, the liquefaction of gases to liquids and the sublimation of solids to vapours.
• The separation of mixtures by evaporation, distillation, fractional distillation, sublimation and crystallization.
• The magnetization and demagnetization of iron rods.

Chemical Change: This is a change which is not easily reversed and in which new substance is formed.

Examples of chemical change include:

• Burning of substance to ash
• The dissolution of metals and limestone in acids
• The rusting of iron.
• The addition of water to quicklime i.e. the slaking of lime.
• Fermentation and decay of substances.
• The changes in the electrochemical cell.

Difference between Physical and Chemical Changes

Physical Change	Chemical Change
It is easily reversible	It is not easily reversible
New substances are formed	New substances are formed
Very little amount of heat is involved	There are remarkable heat change
No change in mass	The new substances always have different masses

ELEMENT, COMPOUND AND MIXTURE

Matter may be classified into elements, compound and mixtures.

Element: An element is a substance which cannot be split up into simpler substances by any known chemical means.

There are 109 known elements. Ninety of them occur naturally, the rest of them are made artificially in the laboratory.   The familiar elements includes iron, gold, tin, oxygen, silver, iodine etc. and the unfamiliar ones includes rubidium, actinium, xenon etc. we use abbreviations or symbols to represent elements, e.g. “O” for oxygen and “H” fro hydrogen.

Elements are grouped as metals, semi-metals or metalloids, and non-metals.

Differences between the Physical Properties of Metals and Non-Metals.

	Metals	Non-Metals
1.	Metals are malleable, ductile or sonorous	Non-metals are not malleable, not ductile or not sonorous
2.	Metals have great tensile strength	Non-metals are brittle or soft
3.	Metals are lustrous	Non-metals are non-lustrous
4.	Metals are good conductors of heat and electricity	They are non-conductors or poor conductors except graphite
5.	They have high melting and boiling point	Non-metals except carbon have low melting and boiling point
6.	They relatively high densities	Non-metals have low densities

Compound: A compound is a substance containing two or more elements which are chemically joined together.

Most substances occurring in nature are compounds. Examples of compound and their component elements are:

Compound	Component Elements	Formula
Water	Hydrogen and Oxygen	H2O
Sand	Silicon and Oxygen	SiO2
Limestone	Calcium, Carbon and Oxygen	CaCO3
Common Salt	Sodium and Chlorine	NaCl
Sugar (Glucose)	Carbon, Hydrogen and Oxygen	C6H12O6
Alcohol (Ethanol)	Carbon, Hydrogen and Oxygen	C2H5OH
Caustic Soda	Sodium, Oxygen and Hydrogen	NaOH

Mixtures: This is formed when two or more substances are physically joined together i.e. they are not chemically joined together. Examples of mixtures and their constituents are:

Mixture	Constituents
Air	Oxygen, carbon(IV)oxide, nitrogen, rare gases, dust, moisture.
Urine	Urea, water, mineral salts
Blood	Water, proteins, fat, oil, sugar, minerals salts, vitamins, hormones, blood cells, haemoglobin, enzymes
Crude oil	Petrol, heavy oil, gas oil, kerosene naptha, bitumen, gas, etc.
Milk	Water, sugar, fat, proteins, mineral salts, vitamin
Brass	Copper, zinc
bronze	Copper, tin

Differences between Mixture and Compound

	Mixture	Compound
1.	The constituents can be separated by physical means.	The constituents cannot be separated by physical means
2.	It may be homogeneous or heterogeneous	It is always homogenous
3.	The properties of a mixture are the sum of those of its individual constituents	The properties of a compound differ entirely from those of its component element
4.	The composition vary	The composition is fixed

QUESTIONS

Lets see how much you’ve learnt, attach the following answers to the comment below

1. Which of the following is an example of a chemical change? (a) dissolution of salt in water (b) rusting of iron (c) melting of ice (d) separating a mixture by distillation
2. Which is the odd-one out? (a) air (b) urine (c) brass (d) sand
3. The addition of water to calcium oxide leads to (a) physical change (b) chemical change (c) formation of a mixture (c) endothermic change
4. A heterogeneous mixture can be defined as any mixture (a) whose composition is uniform (b) whose composition is not uniform (c) formed by solids and liquids (d) of a solute and a solvent
5. Which of the following is a physical change? (a) freezing ice-cream (b) dissolving calcium in water (c) burning kerosene (d) exposing white phosphorus to air

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