Question

When a glass bottle full of vinegar warms up, both the vinegar and the glass expand, but the vinegar expands significantly more with temperature than does the glass. The bottle will break if it is filled up to its very tight cap. Explain why and how a pocket of air above the vinegar prevents the bottle from breaking.

a) Air pressure decreases
b) Air pressure increases
c) Air provides insulation
d) Glass contraction

Answer 1

A glass bottle full of vinegar can break upon warming due to thermal expansion of the liquid. However, a pocket of air above the vinegar absorbs the expansion and prevents the bottle from breaking by reducing internal pressure.

Step-by-step explanation:

When a glass bottle full of vinegar warms up, both the vinegar and the glass experience thermal expansion, but the vinegar expands more than the glass due to its higher coefficient of thermal expansion. If there is no air pocket and the bottle is sealed to its tight cap, the expanding vinegar has nowhere to go and builds up pressure inside the bottle. This increase in pressure can lead to the glass bottle breaking due to the stress exceeding the material's tensile strength.

However, providing a pocket of air above the vinegar allows the air to compress and absorb some of the expansion of the vinegar, thus reducing the pressure buildup inside the bottle. Since gases are compressible, they provide a 'cushion' for the expanding liquid, which then prevents excessive pressure on the bottle walls and can prevent the bottle from breaking.