Sam took out porridge kept in a glass bowl from the refrigerator. As he wanted to have it hot, he put it directly into the microwave oven for heating. To his surprise the glass bowl had cracked!! Can you help him figure out why this had happened? 

Classify the following changes as reversible or irreversible with reasons:

Breaking a rubber band, stretching a rubber band, rolling a dough ball, cooking of pulses, making of ice lollies from juice, ice-cream melting, making a paper boat by paper folding, cutting a paper in the shape of an aeroplane.

Classify the following changes as physical or chemical with reasons:

Melting of iron, rusting of iron, weathering of rocks, cooking of rice, breaking a rubber band, stretching a rubber band, mixing baking soda with lemon juice, mixing sugar and water, making a dough ball, heating the dough ball, heating water to 100°C, cooling water to 0°C.