Ready to level up your chemistry knowledge with a fun, free quiz? In our "Can You Spot a Substance Made of Two or More Elements? Quiz," you'll test your ability to define uniform composition, distinguish a pure substance from a homogeneous mixture, and decide if the components of a homogeneous mixture are visibly distinct - all while sharpening your understanding of what defines a substance made of two or more elements bonded together. Curious to learn even more? Check out our composition of mixtures practice problems or brush up with the classification of matter quiz, then dive into the challenge and prove your skills today!
Which of the following is a pure chemical compound?
Salt (NaCl)
Air
Bronze
Milk
NaCl (table salt) is composed of sodium and chlorine in a fixed 1:1 ratio, making it a pure chemical compound. It cannot be separated by physical methods into its elements. Mixtures like air and bronze contain variable compositions. Learn more about compounds here.
Which term describes a substance with uniform composition throughout?
Homogeneous mixture
Colloid
Element
Heterogeneous mixture
A homogeneous mixture has the same composition and properties throughout the sample. You cannot distinguish its components by simple observation. This uniformity differentiates it from heterogeneous mixtures, which have visible phases. See more on mixtures.
Which of these is an example of a heterogeneous mixture?
Oil and water
Alloy
Salt water
Air
Oil and water form a heterogeneous mixture because the two liquids separate into distinct layers. Each phase has different composition and properties. You can see the boundary between oil and water visually. More on heterogeneous mixtures.
Which of the following contains two or more different elements chemically bonded?
H2O
Ne
Fe
O2
H2O (water) consists of hydrogen and oxygen atoms chemically bonded in a fixed ratio. O2 and Ne are elements, and Fe is a single element (iron). A compound is defined by chemical bonds between different elements. Read more about compounds.
Which of these is a compound and not a mixture?
Carbon dioxide (CO2)
Soil
Stainless steel
Granite
Carbon dioxide is a chemical compound of carbon and oxygen in a fixed 1:2 ratio. The others are mixtures of multiple substances without fixed composition. Compounds have distinct chemical formulas. Explore chemical compounds.
Brass is an alloy of copper and zinc. How would you classify brass?
Compound
Homogeneous mixture
Heterogeneous mixture
Pure substance
Brass is a homogeneous mixture (alloy) because copper and zinc are uniformly mixed at the atomic level but not chemically bonded in a fixed ratio. Alloys have consistent composition but remain mixtures. More on alloys.
Sulfuric acid (H2SO4) is an example of what type of substance?
Compound
Heterogeneous mixture
Homogeneous mixture
Element
H2SO4 is a compound composed of hydrogen, sulfur, and oxygen in a specific ratio. Elements consist of one type of atom only, and mixtures are physical combinations of substances. Sulfuric acid has a single chemical formula, indicating it is a compound. Details on sulfuric acid.
In a mixture of sand and salt, what method can separate the components?
Distillation
Sublimation
Filtration
Chromatography
Filtration separates sand (insoluble) from a salt solution by passing the mixture through a filter. Distillation is for separating based on boiling points, and chromatography is for separating dissolved substances. Sand remains on the filter while the salt solution passes through. Separation techniques.
Which of these describes a colloid rather than a solution?
Air
Sugar in water
Salt water
Milk
Milk is a colloid where tiny fat globules remain dispersed in water, giving a cloudy appearance. Solutions like salt water and sugar water are clear at the molecular level. Air is a homogeneous gas mixture. Learn about colloids.
Air is approximately 78% N2 and 21% O2 by volume. How is air classified?
Element
Pure substance
Mixture
Compound
Air is a mixture because it contains multiple gases that are not chemically bonded in fixed ratios. Although percentages are relatively constant, the components remain separable by physical methods. Compounds have fixed chemical formulas. Details on air as a mixture.
Which formula indicates a compound rather than an element?
CO
Ne
O2
N2
CO is carbon monoxide, a compound of carbon and oxygen. O2 and N2 are diatomic elements, and Ne is a noble gas element. Compounds have chemical bonds between different elements. More on chemical compounds.
Which describes a substance that cannot be separated into simpler substances by physical methods?
Solution
Pure substance
Compound
Mixture
A pure substance has a fixed composition and cannot be separated by physical means. This category includes both elements and compounds. Mixtures and solutions can be separated by filtration, distillation, or other methods. Understanding pure substances.
Which separation technique is best for isolating two liquids with boiling points that differ by less than 5 °C?
Chromatography
Filtration
Simple distillation
Fractional distillation
Fractional distillation uses a fractionating column to provide many vaporization - condensation cycles, allowing efficient separation of liquids with close boiling points. Simple distillation lacks this repeated separation capacity. Filtration and chromatography are not suitable for liquid - liquid separation by boiling point. Learn about fractional distillation.
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Study Outcomes
Understand Uniform Composition -
Explain the concept of uniform composition and define uniform composition in various substances.
Differentiate Pure Substances and Mixtures -
Analyze distinguishing features to differentiate between pure substances and mixtures based on composition and physical properties.
Identify Homogeneous Mixtures -
Describe how components of a homogeneous mixture are visibly distinct or evenly distributed and recognize examples.
Recognize Compounds -
Spot a substance made of two or more elements bonded together by evaluating chemical formulas and bonding patterns.
Classify Substances Accurately -
Apply your knowledge to categorize substances as pure, mixtures, or compounds under various scenarios.
Apply Chemistry Concepts in Practice -
Use interactive quiz questions to test and reinforce your skills in identifying compounds, mixtures, and pure substances.
Cheat Sheet
Uniform Composition Explained -
As per IUPAC guidelines, uniform composition means every sample has identical proportions of its constituents. Compounds exhibit this trait because their elements are chemically bonded in fixed ratios - for example, water (H₂O) always has a 2:1 ratio of hydrogen to oxygen.
Pure Substances: Elements vs. Compounds -
The American Chemical Society defines a pure substance as material with a single type of particle; elements consist of one atom type while compounds contain two or more bonded elements. Sodium chloride (NaCl) is a classic pure compound, whereas iron (Fe) exemplifies a pure element.
Characteristics of Homogeneous Mixtures -
According to NIST, a homogeneous mixture has uniform composition at the molecular level but isn't chemically bonded - its components are not visibly distinct. A saltwater solution is a prime example, and you can separate its components via distillation or evaporation.
Identifying a Substance Made of Two or More Elements Bonded Together -
A compound is by definition a substance made of two or more elements bonded together in fixed proportions (the primary keyword). Carbon dioxide (CO₂) and glucose (C₆H₂O₆) showcase how atoms join to form new materials with unique properties.
Mixtures vs. Pure Substances: Key Differences -
University-level chemistry notes emphasize that mixtures retain individual properties and can be separated physically, while pure substances need chemical reactions for separation. Use the mnemonic "Mix is Mechanical, Pure is Perfect proportions" to recall that mixtures blend without fixed ratios.
