A sealed plastic bag is filled with air. You squeeze the bag and it gets smaller. What state of matter is the air inside?
ASolid — because it pushes back when you squeeze
BLiquid — because it moves around inside the bag
CGas — because it fills the whole bag and can be squeezed into a smaller space
DIt is not matter — air is invisible so it is nothing
Air is a gas. Gases spread out to fill their container and can be compressed (squeezed into a smaller space). The push-back you feel is the gas resisting compression, not a solid property.
Question 2 True / False
Sand pours out of a bucket, so sand is a liquid.
TTrue
FFalse
Answer: False
False. Each grain of sand is a tiny solid that keeps its own shape. When you pour sand, the individual grains slide past each other, which looks like flowing, but each piece is still a solid. A liquid would have no separate pieces — it would be one continuous flowing substance.
Question 3 Short Answer
What is one way you can tell the difference between a solid and a liquid without looking at them?
Think about your answer, then reveal below.
Model answer: You can feel whether it keeps its shape. A solid holds its shape when you pick it up or set it down, while a liquid flows and changes shape to match whatever is holding it.
The key property that separates solids from liquids is shape. Solids have a definite shape of their own. Liquids take the shape of their container. You can discover this by touch — a solid feels firm and holds its form, while a liquid slips and flows through your fingers.