Question

do now

1. classify the changes involved in the following processes as physical or chemical changes (write p or c for each answer only)

(a) photosynthesis
(b) dissolving sugar in water
(c) burning of coal
(d) melting of wax
(e) digestion of food

Explanation:

Step1: Recall definition of chemical change

A chemical change results in new substances being formed with different chemical properties. Photosynthesis is a process where plants use carbon - dioxide and water to produce glucose and oxygen. New substances are formed, so it is a chemical change.

Step2: Recall definition of physical change

A physical change does not result in new substances. Dissolving sugar in water is a physical change as sugar molecules disperse in water but no new chemical substances are formed.

Step3: Analyze burning of coal

Burning of coal involves a reaction with oxygen to produce carbon - dioxide and other by - products. New substances are formed, so it is a chemical change.

Step4: Analyze melting of wax

Melting of wax is a physical change as it only changes the state of wax from solid to liquid without changing its chemical composition.

Step5: Analyze digestion of food

Digestion of food involves chemical reactions in the body to break down complex food molecules into simpler ones. New substances are formed, so it is a chemical change.

Answer:

(a) C
(b) P
(c) C
(d) P
(e) C