Which of these sentences is a physical or chemical change you burn a piece of toast when leaving it in the oven. The bread is now black is that physical or chemical change you forgot to dry a knife. After washing it. The next time you look at it you see reddish brown spots on the blade is that chemical or physical, you are you use a blow dryer to dry your hair is that physical or chemical a straight piece of wire is coiled to form the sprain chemical or physical food color is dropped into water to give it color. Is that physical or chemical change? Chewing food to break it down into smaller particles represents a chemical or physical change but the changing of start and two sugars by enzymes in the digestive system represents a physical physical or chemical change and a firework show the fireworks explode getting off heat and light is that physical or chemical change you crush a piece of chalk into a fine powder. Is that physical or chemical change you dissolve chocolate syrup into a glass of milk and the milk is now shade of brown is that physical or chemical Change, you toast a marshmallow over a campfire until it has a golden brown crust. Is that physical or chemical change you snap a glow stick and it begins to glow a bright yellow color and is warm in your hand is that physical or chemical change?

Answer 1

Here’s a breakdown of each sentence to determine whether it describes a physical or chemical change:

1. You burn a piece of toast when leaving it in the oven. The bread is now black.

   • Chemical Change (The burning of the bread produces new substances, such as carbon.)

2. You forgot to dry a knife. After washing it, the next time you look at it, you see reddish-brown spots on the blade.

   • Chemical Change (The reddish-brown spots indicate rust, which is a new substance formed through the chemical reaction of iron with oxygen and moisture.)

3. You use a blow dryer to dry your hair.

   • Physical Change (The hair dries, but its chemical composition remains the same; water is evaporated.)

4. A straight piece of wire is coiled to form a spring.

   • Physical Change (The wire's shape has changed, but its chemical properties have not.)

5. Food color is dropped into water to give it color.

   • Physical Change (The food coloring disperses in the water without changing its chemical nature.)

6. Chewing food to break it down into smaller particles represents a physical change, but the changing of starch into sugars by enzymes in the digestive system represents a chemical change.

   • This is correct. Chewing is a Physical Change, while the action of enzymes breaking down starches into sugars is a Chemical Change.

7. In a firework show, the fireworks explode, giving off heat and light.

   • Chemical Change (The combustion of the chemicals in fireworks results in new substances and energy production.)

8. You crush a piece of chalk into a fine powder.

   • Physical Change (Crushing changes the form but not the chemical composition of chalk.)

9. You dissolve chocolate syrup into a glass of milk, and the milk is now a shade of brown.

   • Physical Change (Dissolving is a physical process; the chocolate syrup and milk retain their chemical identities.)

10. You toast a marshmallow over a campfire until it has a golden brown crust.

    • Chemical Change (The toasting causes chemical reactions that change the marshmallow's composition.)

11. You snap a glow stick, and it begins to glow a bright yellow color and is warm in your hand.

    • Chemical Change (The chemical reaction inside the glow stick produces light and heat, resulting in new substances.)

In summary:

• Chemical Changes: 1, 2, 5 (mention of enzymes), 6, 7, 10, 11
• Physical Changes: 3, 4, 8, 9