A physical combination of two or more substances that are not chemically bonded, retain their individual properties, exist in variable proportions, and can be separated by physical methods.
Things stirred together but not joined. Each substance keeps its own properties.
Showing a random 20 of 50 problems.
Example 1
medium
A solution contains 20g of sugar dissolved in 80g of water. Find the mass percent of sugar and state whether it is a mixture or compound.
Example 2
hard
Air at sea level is roughly 78%N2, 21%O2, 0.9% Ar, and 0.04%CO2 by volume. Explain why this is a mixture and what would change if it were a compound instead.
Example 3
hard
An unknown clear liquid is heated and the temperature is recorded as it boils. The temperature rises steadily from 78∘C to 100∘C as the liquid evaporates. Is it a pure substance or a mixture? Briefly justify.
Example 4
hard
You add 5.0g of sand to 50g of water. Is the result a solution, suspension, or colloid? Justify briefly.
Example 5
medium
How does separating a mixture differ from decomposing a compound, in terms of energy and method?
Example 6
medium
A student has a clear, colorless liquid. Describe two experimental tests to determine whether it is a pure substance or a mixture.
Example 7
medium
You have iron filings, salt, and sand mixed together. Outline a physical sequence to separate all three.
Example 8
medium
Why does adding more sugar change a sugar-water solution's properties but adding more hydrogen does not change pure water?
Example 9
easy
Classify trail mix (nuts, raisins, chocolate) as a substance type.
Example 10
challenge
Classify and order by separation difficulty: a sand-iron mixture, salt water, and water (a compound).
Seawater contains dissolved salts (∼3.5%), dissolved gases, and suspended particles. Classify seawater as a type of mixture and outline a procedure using at least three separation techniques to isolate the dissolved salt, fresh water, and suspended particles.
Example 13
easy
Can a mixture be separated by physical means? Give one example method.
Example 14
easy
Is a sample of pure copper (Cu) a mixture?
Example 15
medium
60g of a salt-sand mixture is dissolved in water and filtered. The filtrate is evaporated to leave 24g of salt. What mass of sand remained on the filter, and what is the mass percent of salt in the original mixture?
Example 16
medium
Why can the components of a mixture be present in any ratio, unlike a compound?
Example 17
easy
Is air (nitrogen, oxygen, argon, etc.) a mixture?Air: multiple gas species sparsely mixed — a homogeneous gaseous mixture
Example 18
medium
You combine 5.0g of sulfur with 5.0g of iron filings. (a) Before heating, is the result a mixture or compound? (b) After heating until they react to form FeS, is it now a mixture or compound?
Example 19
easy
Is salt water homogeneous or heterogeneous?
Example 20
medium
You need to separate a powder containing salt, sawdust, and iron filings. Outline a step-by-step physical procedure.