AnswersGCSS_Physical Science_ICIntroduction to Chemical Reactions

Introduction to Chemical Reactions Answers

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Cherylanne mixes together Chemical A and Chemical B in a test tube, forming Chemical C. The mixture instantly turns cool to the touch. She then adds Chemical D, and the reaction becomes hot and explodes.

A
Chemicals A and B form an endothermic reaction, and chemicals C and D form an exothermic reaction.
B
Chemicals A and B form an exothermic reaction, and chemicals C and D form an endothermic reaction.
C
Chemicals A and C form an endothermic reaction, and chemicals B and D form an exothermic reaction.
D
Chemicals A and B form an exothermic reaction, and chemicals B and D form an endothermic reaction.
3

Which best describes what happens to the atoms in a chemical reaction?

A
they are rearranged
B
many of them disappear
C
all of them form stronger bonds
D
all of them remain unchanged
4

Two chemicals react in an endothermic reaction. What can be known about this reaction?

A
Heat is absorbed because the old substance needs more energy to break its bonds.
B
Heat is released because the old substance needs less energy to break its bonds.
C
A precipitate will form as a result of the reaction.
D
A gas will form as a result of the reaction.
5

When vinegar and baking soda react, the mixture becomes cold to the touch and a gas and a new liquid substance are formed.

A
The reaction is chemical and endothermic.
B
The reaction is chemical and exothermic.
C
The reaction is non-chemical and endothermic.
D
The reaction is non-chemical and exothermic.
6

Which best explains why a firework being ignited is an example of an exothermic reaction and not an endothermic reaction?

A
The fireworks produce colors.
B
The fireworks give off heat.
C
Igniting the fireworks requires energy.
D
Igniting the fireworks makes an odor.
7

Which of these most likely represents a chemical change?

A
water boiling
B
sugars digested by saliva
C
mud drying to dirt
D
ice cream melting
8

Pedro wants to create a chemical reaction between oil and water. He adds oil to a beaker of water and notices that the liquids do not mix. He then shakes the beaker and the drops of oil become suspended through the water for a few moments before returning to their separate layers.

A
Yes, because the oil was evenly suspended.
B
Yes, because the solution was permanently changed.
C
No, because the oil only briefly mixed with the water.
D
No, because no new substances were formed.
9

Theresa creates an experiment where she mixes two red-colored substances together in a container and observes the solution slowly changing from red to blue for the next eight minutes. The solution becomes completely blue after eight minutes.

A
A chemical change started immediately and finished at eight minutes.
B
A non-chemical change started immediately and finished at eight minutes.
C
A chemical change occurred at four minutes.
D
A non-chemical change occurred at four minutes.
10

Which is an example of a chemical reaction?

A
paper folded into tiny pieces
B
paper burned and turned into smoke
C
paper soaked in water
D
paper shredded and turned into pulp

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