Question

classifying matter review practice

1. identify each substance as either a pure substance or a mixture.
2. if it is a pure substance, state whether it is an element or a compound.

if it is a mixture state whether it is homogeneous or a heterogeneous.
remember:

• pure substances have a fixed composition, and can be described with a single chemical formula.
• mixtures have variable composition, and involve two or more substances physically combined.

material (formula or ingredients listed) is it a pure substance or mixture? for pure substances is it an element or a compound? for mixtures: is it homogeneous (solution) or heterogeneous (mechanical mixture, colloid, suspension)
lactose (c₁₂h₂₂o₁₁)
sugar water (c₁₂h₂₂o₁₁ + h₂o)
gold (au)
pure ethanol (c₂h₅oh)
dirt: (sand + humus + clay)
sodium (na)
filtered air (h₂ + o₂ + n₂ + co₂)
oxygen (o₂)
fructose (c₆h₁₂o₆)
pure water (h₂o)
bottled water (h₂o + dissolved minerals)
iced tea (h₂o + dissolved tea)
chocolate chip ice cream

Explanation:

Step1: Analyze lactose

Lactose ($C_{12}H_{22}O_{11}$) has a fixed - composition and a single chemical formula, so it is a pure substance. Since it is made of multiple elements chemically combined, it is a compound. It is not a mixture.

Step2: Analyze sugar water

Sugar water ($C_{12}H_{22}O_{11}+H_{2}O$) has a variable composition as it is a physical combination of sugar and water. It is a homogeneous mixture (a solution) as the sugar is uniformly dissolved in water.

Step3: Analyze gold

Gold (Au) is a pure substance. It is an element as it consists of only one type of atom.

Step4: Analyze pure ethanol

Pure ethanol ($C_{2}H_{5}OH$) is a pure substance. It is a compound as it is made up of carbon, hydrogen, and oxygen atoms chemically bonded together.

Step5: Analyze dirt

Dirt (sand + humus + clay) is a mixture. It is a heterogeneous mixture as the components (sand, humus, clay) are not uniformly distributed.

Step6: Analyze sodium

Sodium (Na) is a pure substance. It is an element as it consists of only sodium atoms.

Step7: Analyze filtered air

Filtered air ($H_{2}+O_{2}+N_{2}+CO_{2}$) is a mixture. It is a homogeneous mixture as the gases are uniformly mixed at the molecular level.

Step8: Analyze oxygen

Oxygen ($O_{2}$) is a pure substance. It is an element as it consists of only oxygen atoms (in di - atomic form).

Step9: Analyze fructose

Fructose ($C_{6}H_{12}O_{6}$) is a pure substance. It is a compound as it is made up of carbon, hydrogen, and oxygen atoms chemically bonded.

Step10: Analyze pure water

Pure water ($H_{2}O$) is a pure substance. It is a compound as it is made up of hydrogen and oxygen atoms chemically bonded.

Step11: Analyze bottled water

Bottled water ($H_{2}O +$ dissolved minerals) is a mixture. It is a homogeneous mixture as the dissolved minerals are uniformly distributed in the water.

Step12: Analyze iced tea

Iced tea ($H_{2}O+$ dissolved tea) is a mixture. It is a homogeneous mixture as the dissolved tea components are uniformly distributed in the water.

Step13: Analyze chocolate - chip ice cream

Chocolate - chip ice cream is a mixture. It is a heterogeneous mixture as the chocolate chips are not uniformly distributed in the ice - cream.

Answer:

Material (formula or ingredients listed)	Is it a pure substance or mixture?	For pure substances: Is it an element or a compound?	For mixtures: Is it homogeneous (solution) or heterogeneous (mechanical mixture, colloid, suspension)?
sugar water ($C_{12}H_{22}O_{11}+H_{2}O$)	Mixture	N/A	Homogeneous
gold (Au)	Pure substance	Element	N/A
pure ethanol ($C_{2}H_{5}OH$)	Pure substance	Compound	N/A
dirt (sand + humus + clay)	Mixture	N/A	Heterogeneous
sodium (Na)	Pure substance	Element	N/A
filtered air ($H_{2}+O_{2}+N_{2}+CO_{2}$)	Mixture	N/A	Homogeneous
oxygen ($O_{2}$)	Pure substance	Element	N/A
fructose ($C_{6}H_{12}O_{6}$)	Pure substance	Compound	N/A
pure water ($H_{2}O$)	Pure substance	Compound	N/A
bottled water ($H_{2}O +$ dissolved minerals)	Mixture	N/A	Homogeneous
iced tea ($H_{2}O+$ dissolved tea)	Mixture	N/A	Homogeneous
chocolate - chip ice cream	Mixture	N/A	Heterogeneous