You have a graduated cylinder with 50 mL of water. You drop a rock in, and the water level rises to 73 mL. What is the volume of the rock?
A73 mL — that is the new water level
B50 mL — that was the starting water level
C23 mL — the rock displaced that much water, so that is its volume
D123 mL — you add the two numbers together
The rock pushed the water up by 23 mL (73 minus 50). That means the rock takes up 23 mL of space — that is its volume. The rock displaced exactly its own volume of water. This method works for any solid, no matter how oddly shaped.
Question 2 True / False
Volume and weight measure the same thing.
TTrue
FFalse
Answer: False
False. Volume measures how much space an object takes up. Weight measures the pull of gravity on the object. A basketball takes up a lot of space (large volume) but weighs very little. A small lead ball takes up very little space (small volume) but weighs a lot. Volume and weight are two completely different properties.
Question 3 Short Answer
How do you measure the volume of an irregularly shaped object like a rock?
Think about your answer, then reveal below.
Model answer: Use water displacement: partially fill a graduated cylinder with water and record the level. Drop the object in and record the new level. Subtract the first reading from the second — the difference is the object's volume.
When the rock enters the water, it pushes the water aside, making the level rise. The amount of rise equals the rock's volume because the rock displaces exactly as much water as the space it occupies. This method works for any shape, which is why it is used for irregular objects.