Introduction to Chemical Reactions Answers

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1
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Which indicator of a chemical reaction is shown in the picture?

A
the formation of a gas
B
the formation of a precipitate
C
a change in energy
2
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✔ exothermicendothermicneither

A
✔ exothermic
B
endothermic
C
neither
3

✔ exothermicendothermicneither

A
✔ exothermic
B
endothermic
C
neither
4

exothermicendothermic✔ neither

A
exothermic
B
endothermic
C
✔ neither
5

When potassium iodide liquid is poured into lead nitrate solution (both clear solutions), a bright yellow solid, lead iodide, forms in a potassium nitrate solution. What are the signs that this is a chemical reaction? Check all that apply.

A
Heat is produced.
B
Light is produced.
C
Heat is absorbed.
D
Bubbles appear.
E
A precipitate forms.
F
The color changes.
6

Identify the chemical reactions as endothermic, exothermic, or neither.

Answers:
An egg cooking::endothermic
A candle burning::exothermic
Plaster and water combining and becoming warm::exothermic
Salt being added to water, with no change in temperature::neither
7

exothermicendothermicneither

A
exothermic
B
endothermic
C
neither
8

A food item that is left out of the refrigerator turns brown and forms bubbles and gas. What are the signs that this is a chemical reaction? Check all that apply.Heat is produced.Heat is absorbed.Bubbles appear.A precipitate forms.The color changes.

A
Heat is produced.
B
Heat is absorbed.
C
Bubbles appear.
D
A precipitate forms.
E
The color changes.
9

Pure sodium metal placed in water will spark and ignite, as well as form bubbles and gas. What are the signs that this is a chemical reaction? Check all that apply.Heat is produced.Light is produced.Heat is absorbed.Bubbles appear. A precipitate forms.The color changes.

A
Heat is produced.
B
Light is produced.
C
Heat is absorbed.
D
Bubbles appear.
E
A precipitate forms.
F
The color changes.

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Introduction to Chemical Reactions Answers…