Chemical Change

What key words, when present in a question about chemical reactions, might indicate a chemical change is occuring?

• Bubbling

• Condensing

• Dissolving

• Evaporating

Which of the following indicate a chemical reaction is occurring?

• Unknown A dissolves into Unknown B

• Unknown A creates fizzing and bubbles when combined with Unknown B

• Unknown A sinks to the bottom when added to Unknown B

• Unknown A floats to the top when added to Unknown B

Which of the following is a sign that a chemical reaction has occurred?

• change in shape
• melting
• formation of a gas
• dissolving

A solid piece of chocolate is melted and changed to liquid form. Which property of the piece of chocolate will remain the same?

• Texture
• Temperature
  
• Shape
•  Mass

Which of the following is NOT an example of a physical change?

• crumpled paper
• pencil sharpening
• shrunken clothing
• rust

Which of these is a result of a chemical change?

• A mixture
• A solution
• A new substance
• Melting or freezing

When your food energy is made into energy that you use to run, energy is changing from...

• Thermal to chemical

• Chemical to electrical

• Mechanical to electrical

• Chemical to mechanical

Which of the following is a sign that a physical change has occurred?

• Bubbles forming

• The object being broken into smaller pieces

• Heat being produced

• Light being produced

Which of the following is observed here?

• A physical change because you have the same types of atoms

• A physical change because you are just breaking the atoms up

• A chemical change because you are forming a new substance

• A chemical change because atoms are involved

• The baking soda and hydrochloric acid combined, and bubbles formed. 

• The baking soda absorbed the hydrochloric acid. 

• Some of the baking soda dissolved in the hydochloric acid.

• The hydrochloric acid evaporated, leaving only the baking soda.