Joseph Priestley’s Experiments from the 1700s

Priestley lit a candle.

He then placed a glass jar over it…

…and watched as the flame gradually died out.

Priestley lit a candle.

He then placed a glass jar over it…

…and watched as the flame gradually died out.

Priestley reasoned that something in the air was necessary to keep the flame burning.

Priestley then placed fresh mint leaves underneath the jar and allowed the entire setup to sit fora few days.

A few days A few days passed…passed…A few days A few days passed…passed…

After a few days, Priestley found that he could relight thecandle and it wouldburn for a while.

After a few days, Priestley found that he could relight thecandle and it wouldburn for a while.

Priestley concluded that the plant had produced the substance required for burning.

What substance was consumed as the candle burned the first time?

What must have been added to the jar to enable the candle to burn the second time?

Where did this oxygen come from?

What do you think would happen if Priestley had put the plant and candle back in the jar for a few days then once again tried to light the candle?A. the plant would dieB. the plant would light on fire

C. the candle would light againD. the candle would not light again

Suppose Priestley had put the plant and jar into a dark closet for a few days. Do you think the candle would have lit again?

What does this tell you about plants and oxygen?

A. plants do not need oxygenB. plants produce oxygen all the timeC. plants produce as much oxygen as they needD. plants produce oxygen in the presence of light

In another experiment,Priestley put a mouseunder the jar andwaited to see whatwould happen.

In another experiment,Priestley put a mouseunder the jar andwaited to see whatwould happen.

Sadly, the mouse eventually died.

Later, Priestley put a mouse under the jar with fresh mint leaves and waited to see what would happen.

To his surprise, both the mouse and plant survived for quite some time.

What important substance was produced by the plant?

What important substance was produced by the mouse?

Why were both the plant and the mouse able to survive under the jar?

Figure 7-3The products of photosynthesis are the chemical ingredients for cellular respiration, while the products of cellular respiration are the chemical ingredients for photosynthesis.