Mixed or combined

The idea

Substances that are only mixed keep their own properties and can be separated by physical methods, but when the same elements combine chemically to form a compound, the new substance has completely different properties and cannot be separated physically.

Iron and sulfur

Iron filings are black. Sulfur powder is yellow. They are mixed. Then the same two are heated together.

Is the heated product like the mixture?

• No, it is a new substance
• Yes, exactly alike
• It is two separate powders

Mixture or compound

Open both tabs.

Mixture or compound

Only mixed substances keep their properties. A compound has new properties.

Substances only mixed keep their properties and can be separated physically. When elements combine chemically to form a compound, the new substance has different properties and cannot be separated physically.

• Mixture | Compound
• Properties | Each keeps its own | Entirely different
• Separation | By physical methods | Not by physical methods

Notes

Mixture: parts keep properties, separable physically. Compound: new properties, not separable physically.

Check yourself

Iron filings and sulfur powder are only mixed. Iron can be separated using …

Iron sulfide is formed by …

Is iron sulfide attracted by a magnet?

A compound cannot be separated into its elements by …

• a magnet — correct. Yes!
• a candle. A magnet attracts the iron filings.
• a balance. A magnet attracts iron filings.
• just mixing iron and sulfur. Mixing alone gives a mixture. Heating gives iron sulfide.
• heating iron and sulfur — correct. Yes!
• cooling iron and sulfur. Iron sulfide is formed on heating.
• Yes, like iron. The new substance has completely different properties.
• Only when it is black. Iron sulfide is not attracted by a magnet.
• No — correct. Yes!
• physical methods — correct. Yes!
• any method at all. Only physical methods fail. Its elements cannot be separated by them.
• magnets only. Physical methods in general cannot do it.