Q: Which of the following is an example of a container that is filled with a pure substance rather than with a mixture?

OPTIONS:
- a tire filled with air
- a jar filled with salt water
- a balloon filled with helium
- a glass filled with chocolate milk
A: a balloon filled with helium
Q: Which of these is a safe practice in a laboratory investigation when working with chemicals?

OPTIONS:
- pouring unused chemicals down the sink
- mixing leftover chemicals in one container
- wearing safety goggles when working with chemicals
- returning unused chemicals to the original container
A: wearing safety goggles when working with chemicals
Q: Most stars are similar to each other in

OPTIONS:
- brightness.
- composition.
- diameter.
- temperature.
A: composition.
Q: Some events on Earth happen instantly while others take thousands of years to occur. Which process takes the longest time to complete?

OPTIONS:
- rivers rising due to storms and floods
- evaporation of water from the leaves of a plant
- weathering of a rock to form small rocks and sand
- movement of small pieces of rock by flowing water
A:
weathering of a rock to form small rocks and sand