What are some properties of air? (2)
3. Add to Properties of Air chart
Refer to the chart. Add air is compressible to the properties list. Point out that there is now a third column in the chart called Particle Explanation.
Model a response by completing the first row yourself.
The first property is air is invisible. A particle explanation would be air particles are too tiny and too spread out to see. We used Dot Sheet 1 to help us understand this.
Complete the Particle Explanation column for the properties listed so far.
| Properties | Evidence or Reasoning | Particle Explanation |
|---|---|---|
| Air is invisible. | I can see through it. | Air particles are too tiny and too spread apart to see. |
| Air has weight. | I saw the filled balloons tip the balance in the last science class. | Air is matter and each air particle has a tiny bit of weight. |
| Air takes up space. | Air made the plunger of the syringe move. | Air is matter and each air particle takes up a tiny bit of space |
| Air has no odor or taste. | Personal observations. | |
| Air is compressible. | I squeezed the syringes from 12ml to 6ml and when I stopped squeezing, the plunger returned to 12ml. | Air particles have a lot a space between them so they can be squeezed together. |
What's in air?
Explain that although all of the air particles looked the same in the Particle Magnifier, air is actually a mixture of different gases.
Just two gases, nitrogen and oxygen, make up more than 99% of the volume of dry air at ground level. Water vapor in the air varies from a trace to 4%. The amount of water vapor is limited by the temperature of Earth's atmosphere. More than a dozen gases exist in air in tiny amounts, (these are called trace gases) including neon, helium, methane, hydrogen, ozone, carbon monoxide, and sulfur dioxide.
Recap the investigation
Review the key ideas of the investigation:
- Like water, air is made of unimaginably tiny particles.
- Air particles are too small and too spread apart to see.
- The greater space between air particles explains why air is compressible while water is not.
- Air is a mixture of different gases, including water vapor.
