Question

a science teacher demonstrated physical and chemical changes by using a fork to hold a marshmallow over a lit candle. determine which of the following changes during this demonstration are chemical (c) or physical (p). the marshmallow changes shape, the wick turns black, the marshmallow burns, the candle releases smoke, the fork is hot, the wax melts. anthony is performing an experiment. he adds 0.25 grams of baking soda to 5 grams of water and stirs. anthony watches as the baking soda dissolves in the water. if anthony weighs the water in the water before and after this change, what kind of change is this?

Explanation:

Physical changes do not change the substance's chemical composition, like melting wax (a change in state). Chemical changes result in new substances being formed, such as a marshmallow burning (producing smoke and changing its chemical nature), a candle wick turning black (oxidation - a chemical reaction), and baking powder reacting in a baking process (producing gas and new substances). Dissolving soda in water is a physical change as it is a mixture - formation without a chemical reaction creating new substances.

Answer:

• The marshmallow changes shape: Physical (P)
• The wick turns black: Chemical (C)
• The marshmallow burns: Chemical (C)
• The candle releases smoke: Chemical (C)
• The fork is hot: Physical (P)
• The wax melts: Physical (P)
• Dissolving soda in water: Physical (P)
• Baking with baking powder: Chemical (C)