Final answer:
The examples are categorized into physical changes - glass melting, a dentist drilling a tooth and ironing a shirt; and chemical changes - milk being made into cheese, and a newspaper yellowing in the Sun.
Step-by-step explanation:
The examples you've given - glass melting, milk being made into cheese, a dentist drilling a tooth, ironing a shirt, and a newspaper yellowing in the sun, can be categorized as follows:
Physical changes - these do not alter the basic nature of the substance:
- Glass melting: This is a physical change. When heated, glass transforms from a solid state to a liquid state but it remains glass.
- A dentist drilling a tooth: This is also a physical change as the basic material of the tooth is just being reshaped - not turned into a new substance.
- Ironing a shirt: When a shirt is ironed, it gets smooth. But the nature of the shirt doesn't change, so this is also physical.
Chemical changes - these result in a new substance or substances:
- Milk being made into cheese: This is a chemical change. When milk is turned into cheese, bacteria is added to ferment the lactose in the milk into lactic acid, creating a new substance.
- A newspaper yellowing in the Sun: The yellowing of a newspaper is a chemical change because sunlight causes the paper and the ink thereon to undergo a chemical reaction and form new substances.
Learn more about Chemical and Physical Changes