CHAPTER 4 : THE VARIOUS RESOURCES ON EARTH Importance of water to humans and animal : Carries nutrients to all cells in our body. Removes waste (urea) in the urine and sweat. Dissolves chemicals for metabolic activities in cells. Comprises 90% of the cell s protoplasm. Importance of water to plants: Makes food during photosynthesis. Transports organic material (glucose). Supports aquatic plants to stand in water. Importance of soil : Habitat for living things. Humus fertilizes the soil and suitable for farming. Contains mineral salts needed for the growth and development of plants. Importance of living things to human : Provides food as source of energy to carry out living process. Provides building material. Provides clothes to protect body from cold and heat. Importance of oxygen : For respiration of living cell. Needed in burning. Importance of carbon dioxide : Produces food during photosynthesis. Composition in fire extinguishers. Importance of nitrogen : Produces fertilizers. Fills light bulbs to prevent the filament from oxidation. Found in the soil. Importance of mineral : Steel is used for constructions Copper is used to make electric cables. Example : Coal, petroleum and natural gas. Used to generate electricity in power station. Burning of fossil fuels provide energy to vehicles. 1
CHARACTERISTICS A substance which made up of only one type of atom, cannot be broken down into any simpler substances by chemical or physical method. Atom elements consist of individual particles. - examples : Copper, Aluminium, Zink, Iron, Gold. Molecule elements consist of combined atoms of the same type. - examples : Oxygen gas, hydrogen gas. METALS NON- METALS Good electrical conductors Good heat conductors High melting points Shiny appearance High densities Malleable Ductile Sonorous Examples : Aluminium, Gold, Copper, Zink, Iron. Poor electrical conductors Poor heat conductors Low melting points Dull appearance Low densities Brittle Non-ductile Non- sonorous Examples : Bromine, Sulphur, Carbon, Phosphorus, Iodine. USES Copper makes water pipes and electrical cables. Gold - as jewellery. Aluminium makes air craft body. Iron makes cooking utensils. Tin as coating of food cans. USES Carbon as pencil leads Diamond - cut glass and make jewelleries. Sulphur firecrackers and tyres. Nitrogen fertilizers. 2
DEFINATION EXAMPLES OF COMPOUNDS EXAMPLES Sugar Sand Carbon dioxide Salt Chalk Compound are substances made up of two or more elements which are chemically combined. Molecule is the smallest particle in a compound. Examples : A water molecule is made up of two hydrogen atoms and one oxygen atom. Compound Elements present Sodium chloride Sodium, chlorine (salt) Copper sulphate Copper, sulfur, oxygen Calcium Calcium, carbon, carbonate (chalk) oxygen Petrol Hydrogen, carbon Sand Silicone, oxygen Sugar Carbon, hydrogen, oxygen Carbon dioxide carbon, oxygen Water Hydrogen, oxygen Formed by chemical reaction which involve exchange of energy. Properties of compound differs from the properties of its constituents elements. The compound can only be broken down into its elements by chemical methods such as electrolysis. The elements in a compound are joined together in a definite ratio. 3
DEFINATION A mixture consist of two or more substances that have been combined physically. Mixtures can be formed by mixing Different elements Different compounds Elements and compounds Examples : air, soil, orange juice, sea water, milk and etc. Formed by physical methods which does not involved chemical reactions Properties of constituents in a mixture is preserved. Can be separated easily through physical methods. The substances in a mixture can be mixed in indefinite ratio. EXAMPLES OF MIXTURES AND THEIR COMPONENTS Mixture Air Orange juice Sea water Brass (alloy) Blood Steel Coins Coffee drink Components Nitrogen, oxygen, carbon dioxide, dust, rare gases, microorganisms. Orange juice, water, sugar Water, mineral salts Copper, zinc Plasma, blood cells, nutrients, waste products. Iron, carbon Copper, nickel, tin Coffee powder, water, milk, sugar 4
MIXTURE SEPARATING TECHNIQUES 5
DIFFERENCES BETWEEN COMPOUND AND MIXTURES COMPOUNDS MIXTURES Aspect Formed through chemical methods Formation method Formed through physical methods Formed new substances New substances formation Does not form new substances Absorbed or release heat energy Energy changes Does not absorb or release heat energy Combines in fixed ratio Combination ratio of substances Combines in any ratio Cannot be identified Identification of constituents Easily identified Differ from the compounds Properties of constituents Preserved Can use chemical method Separation technique of constituents Can use physical method 6