Science

• Air is a mixture of nitrogen, oxygen, carbon dioxide, noble gases, water vapour and other gases
• Test for oxygen: it relights a glowing splint, it causes a burning splint to burn more brightly
• test for carbon dioxide: it turns hydrogencarbonate indicator from red to yellow, it turns limewater from colourless to milky
• test for water and water vapour. both then dry cobalt chloride paper from blue to pink
• test for nitrogen and noble gases: there’re no simple test
• plants make their own food by photosynthesis
• we can use iodine solution to test for starch. iodine solution changes from brown to blue-black in the presence of starch
• put the leaf in boiling water to destroy the cell membrane
• Put the leaf in hot alcohol to remove the chlorophyll from the leaf
• wash the leaf in hot water to remove the alcohol and make the leaf soft
• add iodine solution to the leaf to test for presence of starch
• Starch and oxygen are produced during photosynthesis
• a food chain shows the feeding relationship and the flow of energy among living things
• in a food chain plants are producers and animals are consumers
• food is the source of energy for all living things
• net gas exchange in plants depends on the relative rates of photosynthesis and respiration
• gas exchange allows a continuous supply of oxygen to the body cells for respiration and removal of carbon dioxide from the body
• Gas exchange in humans takes place at the lung
• Gas exchange at the air sacs: oxygen passes from the air sacs into the blood, carbon dioxide passes from the blood into the air saca
• cigarette smoke contains harmful substances such as tar, nicotine and carbon monoxide. these increase risks of respiratory diseases, heart diseases and lung cancer