Question

1. why does hot air rise in a hot air balloon?

a. hot air weighs more than cold air
b. hot air particles move slower
c. hot air is less dense than cooler air
d. hot air turns into solid matter

1. which observation best shows that air is made of tiny particles?

a. air has a color
b. a balloon changes shape when filled with air
c. air cannot be seen
d. air only exists outdoors

Explanation:

For question 4: Hot air rises because it has lower density than cooler surrounding air, which creates buoyancy. The other options are incorrect: hot air weighs less than cold air, hot air particles move faster, and hot air is a gas not a solid.
For question 5: When a balloon changes shape as air is added, it shows that tiny air particles take up space and push against the balloon's interior. The other options are incorrect: air is colorless, invisibility does not prove it is made of particles, and air exists indoors too.

Answer:

1. C. Hot air is less dense than cooler air
2. B. A balloon changes shape when filled with air