Answer the following question.
Q1. Resporation is a chemical change . Explain.
Q2. Burning of a candle involves both physical and chemical changes. Explain the two types of charges.
Q3. Give two applications of expansion and contraction from day-to-day life.
Answers
Answer:
ANSWER 1) Respiration is a chemical change as new substances like carbon dioxide and water are formed. Also there is change in the mass as glucose is oxidised by oxygen and heat is released. This change is permanent. All these factors conclude that respiration is a chemical change.
ANSWER 2) When a candle burns, both physical and chemical changes occur. Physical Changes: On heating, candle wax gets melted. Since it again turns into solid wax on cooling. ... Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light.
ANSWER 3) Expansion by heating can be used in several everyday activities. The jammed metal lid of a jam jar can be opened by heating. The jar is inverted and just the lid is dipped in hot water. ... The fact that materials expand on heating is used in thermometers
Answer:
3) 1) Engines of motor vehicles run when gases expand. 2) When making steel rims for wheels. 3) When the screw-cap of a bottle cannot be opened