Properties of Matter — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A large rock always has a greater density than a small pebble because it is bigger.
Corrected: A large rock does not always have a greater density than a small pebble because density depends on the type of material, not the size of the object.
Density depends on the type of material, not the size of the object. A small gold nugget is denser than a large block of foam because gold packs more mass into each unit of volume.
2. Fix the sentence:
Volume measures how heavy an object is when you place it on a scale.
Corrected: Volume measures how much space an object takes up, not how heavy it is. Mass measures how heavy an object is.
Volume and mass measure different things: volume is the amount of space an object takes up, while mass is the amount of matter in it. A scale measures mass, not volume.
3. Fix the sentence:
An object sinks in water because it is very large and takes up a lot of space.
Corrected: An object sinks in water because its density is greater than the density of water, not because of its size.
Whether an object sinks or floats depends on its density compared to water, not its size. A tiny steel ball sinks because steel is denser than water, while a huge beach ball floats because it is less dense.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Density is calculated by dividing an object's mass by its volume.
Density equals mass divided by volume, so mass is the measurement you divide by volume to calculate how tightly packed matter is.
2. The amount of space an object takes up is called its volume.
Volume describes how much space an object occupies, measured in units like cubic centimeters or liters.
3. An object with a density less than 1 g/cm³ will float in water.
Water has a density of 1 g/cm³, so any object with a lower density is lighter than the same volume of water and floats on the surface.
4. Scientists use a balance to measure the mass of an object in grams.
A balance compares an unknown object against known masses to find its mass in grams, making it the standard tool for measuring how much matter an object contains.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. A wooden block and a steel marble are the same size. The steel marble sinks in water but the wooden block floats. Explain why.
Sample answer: The steel marble has a greater density than water so it sinks, while the wooden block has a lower density than water so it floats. Even though they are the same size, steel is a denser material than wood.
A good answer includes: The steel marble has a greater density than water so it sinks, while the wooden block has a lower density than water so it floats. Even though they are the same size, steel is a denser material than wood.
2. Explain how you can find the volume of an irregularly shaped rock using water.
Sample answer: You can place water in a graduated cylinder and record the level. Then drop the rock in and record the new water level. The difference between the two levels equals the volume of the rock.
A good answer includes: You can place water in a graduated cylinder and record the level. Then drop the rock in and record the new water level. The difference between the two levels equals the volume of the rock.