Evidences of Chemical Reactions and Changes

The video explores evidences of chemical reactions, including precipitate formation, energy change, unexpected color change, smell change, and gas production. A mnemonic device is introduced to help remember these evidences. Each evidence is explained with examples, such as milk curdling for precipitate and rusting for color change.

What is a chemical reaction?

• A process where substances interact to form new substances.

• A physical change in the state of a substance.

• A process of mixing two substances without any change.

• A change in the temperature of a substance.

What mnemonic device can help remember the evidences of chemical reactions?

• Please excuse coughs, sneezes, and burps.

• Never eat soggy waffles.

• My very educated mother just served us noodles.

• King Philip came over for good soup.

Which of the following is an example of a precipitate?

• Salt dissolving in water.

• Vinegar curdling milk.

• Sugar melting in a pan.

• Ice melting into water.

What happens when vinegar is added to milk?

• A precipitate forms.

• The milk freezes.

• The milk turns blue.

• The milk evaporates.

What type of reaction occurs when a hand warmer is activated?

• Exothermic reaction.

• Endothermic reaction.

• Color change.

• Physical change.

What is an example of an endothermic reaction?

• Hand warmers activating.

• Ice melting.

• Baking soda and vinegar reaction.

• Lighting a fire.

Which of the following is NOT an example of an unexpected color change?

• Mixing red and blue paint.

• Copper turning green.

• Rust forming on iron.

• Burning a match.

What evidence of a chemical reaction is indicated by the smell of cookies baking?

• Unexpected color change.

• Energy change.

• Smell change.

• Precipitate formation.

Which of the following is a sign of gas production during a chemical reaction?

• Formation of a solid.

• Bubbles forming.

• Change in temperature.

• Color change.

Which of the following is a chemical reaction involving gas production?

• Melting butter.

• Dissolving sugar in tea.

• Baking soda reacting with vinegar.

• Mixing oil and water.