5_physical/chemical change

Question 1

Physical Change

Answer 1

The change of a substance’s physical property. No change in composition, no formation of new substances.

Question 2

Chemical Change

Answer 2

The formation of a new substance.

Question 3

5 indicators of chemical change:

Answer 3

• unexpected change in colour
• change in odor
• unexpected production of energy (change in tempereature/light)
• chemical precipitation occurs (where a solid is formed beneath a liquid solution)

Question 4

Explain if a sugar cube dissolving into a cup of water is a physical or chemical change.

Answer 4

The sugar particles become diluted into the water and spread out evenly, however none of the five indicators of chemical change occur.

Question 5

What is the Electrolysis of Water?

Answer 5

A process using electrical energy to turn H2O water into H2 hydrogen gases and O oxygen. It is performed using the Hoffman Apparatus.

Question 6

How is Electrolysis of Water an example of chemical change? What can you do as evidence to support your reasoning?

Answer 6

H2 and O are new substances formed out of H2O. The glowing splint test can be used to identify oxygen gas, where the stick catches on fire. The flaming splint can be used to identify hydrogen gas, where the stick pops.

Question 7

Why is salt applied to sidewalks and driveways in the winter times?

Answer 7

When salt is dissolved into ice or water, it creates saltwater. Salt water is much denser than pure water. The greater the concentration, the greater its ability to decrease water’s freezing and melting point. Therefore, salt will allow the ice to melt even at low temperatures and reduce the formation of ice, making sidewalks and driveways safer to commute on.