recognizing chemical reactions

examples of chemical reactions

Look carefully at the Figures 1.1, 1.2, and 1.3. All of the photos demonstrate chemical reactions. For each photo, identify a sign that one or more chemical reactions have taken place. A burning campfire can warm you up on a cold day. Dissolving an antacid tablet in water produces a fizzy drink. Adding acid to milk produces solid curds of cottage cheese. Q: Did you ever make a volcano by pouring vinegar over a mountain of baking soda? If you did, you probably saw the mixture bubble up and foam over. Did a chemical reaction occur? How do you know? A: Yes, a chemical reaction occurred. You know because the bubbles are evidence that a gas has been produced and production of a gas is a sign of a chemical reaction.

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whats your sign

A change in color is just one of several potential signs that a chemical reaction has occurred. Other potential signs include: Change in temperature-Heat is released or absorbed during the reaction. Production of a gas-Gas bubbles are released during the reaction. Production of a solid-A solid settles out of a liquid solution. The solid is called a precipitate. Click image to the left or use the URL below. URL:

instructional diagrams

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questions

all changes in matter are the result of chemical reactions.

a. true

-->  b. false

signs that a chemical reaction has occurred include a change in

a) temperature.

b) color.

c) state.

-->  d) two of the above

which of the following is a sign of a chemical reaction?

a) a liquid changes to a solid.

b) a liquid changes to a gas.

c) a solid changes to a gas.

-->  d) a gas is released from a liquid.

the solid lumps in cottage cheese are an example of a precipitate.

-->  a. true

b. false

the release of gas bubbles is a sign of a chemical reaction.

-->  a. true

b. false

which of the following does not involve chemical reactions?

a) leaves change color in the fall.

-->  b) a pond freezes over in the winter.

c) a fire burns a pile of fallen leaves.

d) fallen leaves decay in a compost pile.

diagram questions

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