AnswersChemistry 1A - Mr. KaanLab: Ionic and Covalent Bonds

Evidence of Chemical Reactions Answers

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Two different liquids are mixed together. Which observation indicates that an exothermic chemical reaction has taken place?

A
an increase in volume
B
a decrease in volume
C
a rise in temperature
D
a drop in temperature
2
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When sodium metal is added to water, an orange flame is observed on the metal surface. Based on this observation, what can best be concluded?

A
A physical change occurs because the metal gets smaller.
B
A chemical reaction occurs because the liquid becomes cloudy.
C
A chemical reaction occurs because heat and light are given off.
D
A physical change occurs because vapor is released into the air.
3

Burning a piece of wood in fire can be best described as a

A
chemical change because the atoms in wood change their state.
B
physical change because the atoms in wood are turned into a gaseous product.
C
chemical change because the atoms in wood and oxygen are rearranged.
D
physical change because the atoms in wood are turned into black ash.
4

A piece of limestone erodes due to acid rain. This process can be best described as a

A
slow chemical change.
B
rapid chemical change.
C
slow physical change.
D
rapid physical change.
5

The images show two unrelated events occurring at separate times. Which event is most likely an example of a chemical reaction?

Question illustration
A
Event 1 because there is a color change.
B
Event 1 because there is a release of heat and light.
C
Event 2 because the temperature is dropping in the liquid.
D
Event 2 because the blue color mixes throughout the liquid.
6

The images show two processes. Image A: a roasting marshmallow Image B: melting iceWhich statement about the two images is true?

Question illustration
A
Image A shows a physical change, and image B shows a chemical reaction.
B
Image A shows a chemical reaction, and image B shows a physical change.
C
Both images show chemical reactions that are endothermic.
D
Both images show chemical reactions that are exothermic.
7

During an experiment, Mr. Lehman tells his students to be alert for signs that an endothermic reaction is happening. Which of the following scenarios would his students most likely observe?

A
A test tube becomes cool to the touch.
B
A liquid appears to glow.
C
A new odor comes from a beaker.
D
A solid forms from a mixture of solutions.
8

Which is the most important question for deciding if a chemical reaction has occurred?

A
Was there a change in the size?
B
Was any heat energy given off?
C
What is the density of the substance?
D
What is the texture of the substance?
9

Among these processes, which is the slowest chemical reaction?

A
digesting food
B
boiling an egg
C
tarnishing of silver
D
melting of a glacier
10

Which statement describes a chemical reaction?

A
Atoms in the products are rearranged to form new substances.
B
Atoms in the reactants are rearranged to form new substances.
C
Atoms in the products change into new atoms to form new substances.
D
Atoms in the reactants change into new atoms to form new substances.

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