Round 3: Understanding Compounds and Mixtures

Which situation best demonstrates the difference between a compound and a mixture?

• Mixing salt and pepper in a container

• Dissolving sugar in water

• Reacting hydrogen with oxygen to form water

• Stirring sand and iron filings

A student is given a white crystalline substance. How can they determine if it is a compound or a mixture?

• Check if it is solid

• Try to separate it by physical means

• Smell the substance

• Measure its density

Iron (Fe) is classified as an element. Which best justifies this classification?

• It can be separated into simpler substances

• It contains two or more atoms

• It cannot be broken down by chemical means

• It reacts with oxygen

A compound contains only carbon and oxygen. What conclusion can be drawn if the compound does not conduct electricity?

• It is likely a metallic compound

• It is an ionic compound

• It contains nonmetals and likely covalent

• It is a mixture of gases

Which change indicates the formation of a new substance and supports the idea of a chemical change in matter?

• Water boils

• Ice melts

• Vinegar reacts with baking soda to form bubbles

• Salt dissolves in water

Why is it incorrect to classify air as a compound?

• Air contains only one kind of atom

• Air has a constant composition

• Air can be separated by chemical means

• Air is a mixture of gases that retain their properties

An unknown sample conducts electricity and is malleable. Which type of element is it most likely to be?

• Nonmetal

• Metalloid

• Metal

• Compound

Why are metalloids unique in the periodic table?

• They conduct heat well but not electricity

• They share properties of both metals and nonmetals

• They are found only in compounds

• They are gases at room temperature

Which best explains why compounds have fixed compositions while mixtures do not?

• Compounds are made from elements bonded in exact ratios

• Mixtures are not composed of atoms

• Mixtures contain only one type of molecule

• Compounds are physically combined

Which observation indicates that a sample is a compound and not a mixture?

• It has uniform appearance

• It can be separated by filtration

• It has different components visible

• It forms new properties when its elements combine