Evidence of Chemical Reactions

Question 1

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?

Revolt · Accepted Answer

A chemical reaction occurs because heat and light are given off.

Question 2

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

Revolt · Accepted Answer

Image A shows a chemical reaction, and image B shows a physical change.

Question 3

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

Revolt · Accepted Answer

a rise in temperature

Question 4

Among these processes, which is the slowest chemical reaction?

Revolt · Accepted Answer

tarnishing of silver

Question 5

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

Revolt · Accepted Answer

Was any heat energy given off?

Question 6

The chemical formula below shows how salt is produced.HCl + NaOH NaCl + H2O Which substances are the reactants?

Revolt · Accepted Answer

HCl and NaOH

Question 7

Which term best describes the role of hydrogen gas in the formation of a water molecule?

Revolt · Accepted Answer

reactant

Question 8

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

Revolt · Accepted Answer

chemical change because the atoms in wood and oxygen are rearranged.

Question 9

Which statement about a chemical reaction is true?

Revolt · Accepted Answer

It occurs whenever a chemical change takes place.

Question 10

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

Revolt · Accepted Answer

slow chemical change.

Evidence of Chemical Reactions Answers