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What is a precipitate?

1. AA substance that speeds up a reaction
2. BA liquid that forms when a solid melts
3. CAn insoluble solid that forms when two solutions react
4. DA gas that bubbles out when two solutions are mixed

Which method separates sand from water?

1. ADistillation
2. BEvaporation of the sand
3. CFiltration
4. DChromatography

What is the change from a gas directly to a solid, skipping the liquid state, called?

1. ASublimation
2. BCondensation
3. CFreezing
4. DDeposition

A red blood cell is placed in a concentrated (hypertonic) salt solution. What happens?

1. AThe cell stays the same size and shape
2. BWater enters the cell, which swells and may burst
3. CSalt leaves the cell, which swells
4. DWater leaves the cell, which shrinks

How does a mixture of iron filings and sulfur powder differ from the compound iron sulfide?

1. AThe mixture can be separated physically, for example with a magnet
2. BThe mixture has a fixed ratio of iron to sulfur
3. CThe mixture is formed by a chemical reaction between the two elements
4. DThe compound keeps the magnetic properties of iron

What are London dispersion forces?

1. AWeak, temporary attractions caused by shifting electrons in molecules
2. BStrong bonds formed by transferring electrons
3. CAttractions between a hydrogen atom and a metal ion
4. DForces that hold protons together in the nucleus

Ethanol (CH₃CH₂OH) and dimethyl ether (CH₃OCH₃) have the same formula, C₂H₆O, but ethanol boils at a much higher temperature. Why?

1. AEthanol has an O–H group, so its molecules form hydrogen bonds with each other
2. BEthanol molecules are heavier than dimethyl ether molecules
3. CDimethyl ether is ionic and ethanol is covalent
4. DEthanol has more carbon atoms

Making ammonia (N₂ + 3H₂ ⇌ 2NH₃) is exothermic. A low temperature would give a higher yield, yet factories use a moderately high temperature. Why?

1. AHigher temperatures shift the equilibrium toward more ammonia
2. BLow temperatures would make the ammonia explode
3. CAt low temperatures the reaction is too slow to be useful
4. DThe catalyst only works when the reaction is endothermic