Classification of Matter: Quiz

Classification of Matter: Quiz

7 questions

1. Question 1EasyWhich of these is a compound?

   AOxygen gas, $\ce{O2}$BAirCCarbon dioxide, $\ce{CO2}$DBrass
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   Answer: Carbon dioxide, $\ce{CO2}$

   CO₂ contains two different elements bonded in a fixed ratio. O₂ is an element; air and brass are mixtures.

2. Question 2EasyWhich is a heterogeneous mixture?

   ASalt waterBAirCOil and waterDDistilled water
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   Answer: Oil and water

   Oil and water form separate layers, so the mixture is not uniform. Salt water and air are uniform (homogeneous); distilled water is a pure compound.

3. Question 3EasyWhich change is chemical?

   AWater boilingBWood burningCSalt dissolving in waterDGlass breaking
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   Answer: Wood burning

   Burning forms new substances (carbon dioxide, water, ash). The other changes do not change what the substance is.

4. Question 4MediumWhat is the best way to obtain solid salt from salt water?

   AFiltrationBEvaporationCUsing a magnetDChromatography
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   Answer: Evaporation

   The salt is dissolved, so it passes through a filter. Evaporating the water leaves the salt behind.

5. Question 5MediumWhich statement about compounds is correct?

   ATheir composition can vary from sample to sampleBThey can be separated into elements by filteringCTheir elements are combined in a fixed ratio by massDThey keep the properties of their elements
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   Answer: Their elements are combined in a fixed ratio by mass

   This is the law of definite proportions. Compounds have new properties and can be broken down only by chemical reactions.

6. Question 6MediumWhich is a chemical property?

   ADensityBBoiling pointCFlammabilityDColour
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   Answer: Flammability

   Flammability describes how a substance reacts (burns). The others can be observed without changing the substance.

7. Question 7HardA clear, colourless liquid boils over a range of temperatures instead of at one fixed temperature. What does this suggest?

   AIt is an elementBIt is a pure compoundCIt is a mixtureDIt is undergoing a chemical change
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   Answer: It is a mixture

   Pure substances have a sharp, fixed boiling point at a given pressure. Boiling over a range is typical of a mixture.