Question

name
directed reading a continued
chemical changes and new substances

1. chemical changes are the processes by which substances

a. move from place to place.
b. change into new substances.
c. change in their physical properties.
d. become greater in mass.

1. which of the following would not be considered an example of a chemical change?

a. the bubbling action of effervescent tablets
b. the green coating on copper statues
c. the melting of a popsicle
d. the burning of rocket fuel

1. how do you know that baking a cake involves chemical changes?

1. list some signs or clues that show that a change you are observing is a chemical change?

Explanation:

1. Chemical changes result in new substances.
2. Melting a Popsicle is a physical change (change of state from solid to liquid), not a chemical change. Effervescent tablets involve gas - producing reactions, green coating on copper is due to oxidation, and burning of rocket fuel is a combustion reaction.
3. Baking a cake involves chemical changes as ingredients like flour, eggs, and baking powder react to form a new substance with different properties. There are chemical reactions such as the decomposition of baking powder to produce carbon dioxide gas which causes the cake to rise, and proteins in eggs denaturing.
4. Signs of a chemical change include production of gas (bubbles), formation of a precipitate, color change, temperature change (exothermic or endothermic), and change in odor.

Answer:

1. b. change into new substances.
2. c. the melting of a Popsicle
3. Ingredients react to form a new substance with different properties. Chemical reactions like decomposition of baking powder and protein denaturing occur.
4. Production of gas, formation of precipitate, color change, temperature change, change in odor.