Question

stemscopedia: stop and jot
whenever you reach a stop and jot question in the stemscopedia, stop and jot your response to it here.

1. when a cake is baked, is a new substance created?
2. do you think the property of magnetism is a physical property or a chemical one? why?
3. name a physical change and a chemical change associated with burning a candle. explain how you know.
4. name three physical changes that you can think of and explain how you know they are physical changes.

Explanation:

Step1: Analyze cake - baking

Baking a cake involves chemical reactions like the reaction of baking powder with moisture to produce carbon - dioxide gas, and proteins in flour denaturing. These chemical reactions create new substances with different chemical properties. So, a new substance is created when a cake is baked.

Step2: Determine magnetism property

Magnetism is a physical property. Physical properties can be observed or measured without changing the substance's chemical identity. Magnetism does not change the chemical composition of a substance. For example, a magnet can attract iron filings without changing the iron's chemical makeup.

Step3: Identify candle - burning changes

Physical change: The melting of the wax. We know it's a physical change because the wax changes from solid to liquid, but its chemical composition remains the same. Chemical change: The burning of the wick and wax to produce carbon - dioxide, water vapor, and heat. We know it's a chemical change because new substances are formed with different chemical properties.

Step4: List and explain physical changes

1. Melting ice: Ice changes from solid to liquid water. The chemical composition of water ($H_2O$) remains the same, so it's a physical change.
2. Tearing paper: The paper is physically divided into smaller pieces, but its chemical composition (cellulose and other components) does not change.
3. Dissolving salt in water: Salt ($NaCl$) dissociates in water, but both salt and water retain their chemical identities. It is a physical change as no new chemical substances are formed.

Answer:

1. Yes, a new substance is created when a cake is baked.
2. Magnetism is a physical property because it can be observed without changing the chemical identity of a substance.
3. Physical change: Melting of wax (chemical composition of wax remains the same). Chemical change: Burning of wick and wax (new substances like carbon - dioxide and water vapor are formed).
4. Melting ice (chemical composition of water remains $H_2O$), tearing paper (chemical composition of paper remains the same), dissolving salt in water (salt and water retain their chemical identities).