chap 3 (elements, compounds, mixtures)

What is an element?

A pure substance that cannot be broken down into simpler substances by chemical methods.

Is an element a pure substance?

Yes, an element is always a pure substance.

What is a compound?

A pure substance made of two or more elements chemically combined in a fixed ratio by mass.

Is a compound a pure substance?

Yes, a compound is a pure substance.

What is a mixture?

A combination of two or more substances that are not chemically joined together.

Is a mixture a pure substance?

No, a mixture is NOT a pure substance.

Why do mixtures have variable composition?

Because substances in a mixture can be mixed in any proportion.

Why do compounds have fixed composition?

Because elements in a compound are chemically combined in fixed ratios by mass.

Can elements in a compound be separated by physical means?

No, they require chemical processes to separate.

Can substances in a mixture be separated by physical means?

Yes, by methods like filtration, distillation, chromatography.

What is a solute?

The substance that dissolves in a solvent.

What is a solvent?

The substance that dissolves the solute to form a solution.

What is a solution?

A clear mixture in which a solute is dissolved in a solvent.

What is a suspension?

A mixture where a solid does not dissolve and forms a cloudy mixture.

Why is a solution clear?

Because solute particles are very small and allow light to pass through.

Why is a suspension cloudy?

Because solid particles are large and scatter light, blocking it.

Do solute particles settle in a solution?

No, they remain evenly spread and do not settle.

Do particles settle in a suspension?

Yes, solid particles settle to the bottom when left to stand.

Can solution particles pass through filter paper?

Yes, because they are extremely small.

Can suspension particles pass through filter paper?

No, suspended solid particles are too large.

What is residue?

The insoluble solid left behind on filter paper during filtration.

What is filtrate?

The liquid that passes through filter paper during filtration.

What does soluble mean?

Able to dissolve in a liquid.

What does insoluble mean?

Unable to dissolve in a liquid.

Why do dissolved solute particles become invisible?

Because they separate into tiny particles spread evenly throughout the solution.

What is solubility?

The maximum amount of solute that can dissolve in a fixed amount of solvent at a given temperature.

What is a dilute solution?

A solution with a small amount of solute in a large volume of solvent.

What is a concentrated solution?

A solution containing a large amount of solute compared to the solvent.

What is a saturated solution?

A solution that contains the maximum amount of solute that can dissolve at a given temperature.

How do you know a solution is saturated?

No more solute can dissolve and extra solute remains undissolved.

What factors affect solubility?

Type of solute, type of solvent, and temperature of solvent.

What factors affect rate of dissolving?

Temperature, surface area of solute, and stirring.

How does temperature affect dissolving rate?

Solids dissolve faster at higher temperatures.

How does stirring affect dissolving rate?

Stirring spreads dissolved particles faster, increasing dissolving speed.

How does surface area affect dissolving rate?

Smaller pieces dissolve faster due to larger surface area.

What are metals?

Elements that are generally shiny, malleable, ductile and good conductors of heat and electricity.

What are non-metals?

Elements that are usually dull, poor conductors, and brittle in solid form.

Are metals good conductors?

Yes, metals conduct heat and electricity well.

Are non-metals good conductors?

No, they are generally poor conductors.

What does malleable mean?

Can be hammered or beaten into different shapes without breaking.

What does ductile mean?

Can be drawn into thin wires without breaking.

Do metals corrode?

Some do, but metals like gold do not corrode easily.

Do non-metals corrode?

No, non-metals do not corrode.

How are elements arranged in the Periodic Table?

By their properties and atomic structure.

At room temperature, what state is hydrogen?

Gas.

At room temperature, what state is mercury?

Liquid.

At room temperature, what state is iron?

Solid.

How to identify elements in a compound from the chemical name?

Names ending in '-ide' usually contain two elements; names with oxygen often end in '-oxide' or '-ate'.

What elements are in sodium chloride?

Sodium and chlorine.

What elements are in magnesium oxide?

Magnesium and oxygen.

What elements are in sulfur dioxide?

Sulfur and oxygen.

What elements are in copper sulfate?

Copper, sulfur, and oxygen.

What elements are in iron carbonate?

Iron, carbon, oxygen.

What does the formula H₂O represent?

Water made of hydrogen and oxygen.

What does the formula CaCO₃ represent?

Chalk made of calcium, carbon and oxygen.

Compare mixtures and compounds in terms of properties.

Mixtures keep the properties of their components; compounds have entirely new properties.

Compare mixtures and compounds in terms of separation.

Mixtures use physical separation; compounds need chemical separation.

Why can’t compounds be separated physically?

Because their elements are chemically bonded.

Why can mixtures be separated physically?

Because no chemical bonds hold their components together.