1. Classify the changes involved in the following processes as physical or
chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f) Digestion of food
State whether the following statements
Answers
Answer:
a. chemical changes
b. chemical changes
c. physical changes
d. physical changes
e. physical changes
f. chemical changes
Explanation and reasons:
●a. Chemical change occurs because photosynthesis is the process in which plants make food with the help of water ,CO2 ,sunlight and chlorophyll and it all of these result in a chemical reaction so chemical change occurs.
●b. Chemical changes occurs because when we mix water and sugar ,a homogeneous mixture is formed and sugar is solid and water is liquid but sugar completely dissolves in water and the result is sugar water so chemical change occurs.
●c. Physical change occurs because when we burn coal it only changes its form meaning it only turns into coal ashes which is also small particles of coal .It doesn't turn into something else or a chemical reaction takes place so physical change occurs.
●d. Physical changes occurs because when the wax melts it just turns into its liquid form .It doesn't turn into anything else or a chemical reaction takes place so physical changes occurs.
●e . Physical changes occur because we are just beating aluminium to make aluminium foil . It still remains aluminium. it doesn't turn into anything else or a chemical reaction takes place. so physical changes occur.
●f. chemical changes occurs because when our food is being digested it is crushed , mashed, and gastric juices and bile are mixed with the thick consistency. and a chemical reaction takes place that results in breaking the food down more .so chemical change occurs.