 |
|
|
|
|
|
|
|
 |
|
||||||
 |
 |
 |
|
||||
 |
 |
 |
 |
 |
|
||
 |
|
||||||
 |
 |
 |
 |
|
|||
 |
|
||||||
 |
|
||||||
|
|
|
|
 |
 |
|
|
 |
|
||
 |
 |
|
|
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
 |
|
|
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
 |
 |
|
 |
|
||
 |
|
||
 |
|
||
The next evidence for photosynthesis is from the experiments of Joseph Priestley. Priestley was an Englishman who had been investigating gases, particularly oxygen. Gases, or vapours as they were called by most people of the time, were little understood. Vapours were thought to cause diseases. People closed their windows and covered their faces to try to protect themselves from vapours. Priestley, and other scientists of the 1700s, wanted to logically investigate what gases were and what they did. Priestley's first experimentJoseph Priestley had observed that a candle burning in a sealed jar soon went out. If a mouse was then put into the jar it soon suffocated. This was because burning uses up oxygen in the air. Animals need to breathe in oxygen. What are the important points in the passage above?
Think about this experiment and then try the following activity.
|
|||||||||||||||||||||||||||||||||||||
 |
Lesson 7 - Photosynthesis |
|
|||||||||||||||||||||||||||||||||||
