Properties of Matter — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A pure substance made of only one type of atom is called an element.
Elements are the simplest pure substances — only one kind of atom. Examples: oxygen (O), gold (Au), carbon (C).
2. Water is a compound because it is made of hydrogen and oxygen chemically combined.
A compound is formed when two or more elements chemically bond in a fixed ratio. Water = H₂O.
3. A salad is a mixture because its parts can be physically separated.
A mixture contains two or more substances that are not chemically combined and can be separated.
4. Gold and oxygen are both examples of elements found on the periodic table.
All elements appear on the periodic table. They cannot be broken down into simpler substances by chemical means.
5. Table salt has the chemical formula NaCl, which means it is a compound of sodium and chlorine.
NaCl = sodium (Na) + chlorine (Cl) chemically bonded. This is a compound with specific fixed properties.
6. A solution is a type of homogeneous mixture that looks the same throughout.
Homogeneous mixtures are uniform throughout. Saltwater, air, and lemonade are homogeneous mixtures.
7. Trail mix is a heterogeneous mixture because you can see the different pieces.
Heterogeneous mixtures are not uniform — different components are visible and can be separated easily.
8. In a compound, the elements are combined in a fixed ratio that does not change.
Water is always H₂O (2:1 hydrogen to oxygen). Fixed ratios distinguish compounds from mixtures.
9. Unlike a compound, a mixture can be separated using physical methods like filtering.
Mixtures can be separated by physical methods: filtering, evaporation, magnetism, or picking. Compounds require chemical reactions to separate.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Oxygen
→ Element — a pure substance made of only one type of atom
Homogeneous mixture — salt dissolved evenly throughout water
Saltwater
→ Homogeneous mixture — salt dissolved evenly throughout water
Heterogeneous mixture — different pieces can be seen and separated
Carbon dioxide
→ Compound — carbon and oxygen atoms chemically bonded together
Element — a pure substance made of only one type of atom
Trail mix
→ Heterogeneous mixture — different pieces can be seen and separated
Compound — carbon and oxygen atoms chemically bonded together
Oxygen=element(idx2); Saltwater=homogeneous mixture(idx0); Carbon dioxide=compound(idx3); Trail mix=heterogeneous mixture(idx1)