7.P.2B.4 Chemical and Physical Changes

Bubbles and fizzing can be seen instantly when baking soda is mixed with vinegar.  The bubbles are evidence of which of the following?

• A gas is formed when baking soda and vinegar are mixed.
• Baking soda dissolves in vinegar when they are mixed.
• Vinegar turns into alcohol when it is mixed with baking soda.
• A precipitate is formed when baking soda and vinegar are mixed.

A student mixes two clear liquids together.  After a few minutes, a white powder can be seen settling on the bottom of the test tube.  Which of the following is a conclusion that the student can draw based on these observations?  The two clear liquids-

• have combined to produce a new substance.
• were pure substances before they were mixed.
• are toxic and should be handled with extreme caution.
• have been stored too long and are no longer good.

Which of the following characteristics is shared by all chemical reactions?

• Produce a precipitate
• Show a color change
• Release heat energy
• Form new substances

All of the following are evidence of a chemical change EXCEPT-

• change in state of matter
• formation of a gas
• color change
• precipitate forms

Students combine several chemicals and record the observations in their science notebooks.  A list of the observed results is given here.
-Production of a gas (bubbles)
-Phase change (solid to liquid)
-A precipitate (solid) forms
-Change in shape
-Crystals dissovling
-Heat produced
How may of the observations are evidence that a new substance was formed?

• 3
• 4
• 5
• 6

Which of the following observations is the best indicator that a new substance has been formed?

• A solid has become a liquid.
• A substance has changed color.
• A solid has dissolved in a liquid.
• The volume of a substance increased.

What kind of properties can only be observed when a substance changes into a different substance?

• physical properties
• chemical properties
• liquid properties
• real properties

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

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

Is burning wood a chemical or physical change?

• chemical
• physical

Photosynthesis (Water, Carbon dioxide and sunlight reacting and creating Oxgyen and Glucose) is an example of a

• physical change
• chemical change