Final answer:
A glass bottle used for vinegar or oil in salad dressing is a cruet. Fluid ounces are the most precise unit for labeling small bottles like those for barbecue sauce. An air pocket in a bottle helps prevent breakage by allowing space for the vinegar to expand when heated.
Step-by-step explanation:
The glass bottle used to hold vinegar or oil for salad dressing is called a cruet. When talking about the measurement of barbecue sauce, the most accurate unit for the bottles about the size of a water bottle would be fluid ounces, since it is the smallest unit and allows for a more precise label. In regards to why a glass bottle filled with vinegar will break if it warms up and is filled to the top with no air pocket, it is because substances expand when they are heated, and vinegar expands more than glass. This can cause the bottle to break if there is no room for the vinegar to expand into. An air pocket allows for expansion and can prevent the glass from breaking.
In terms of identifying substances, white wine is a homogeneous mixture (solution), mercury is an element, ranch-style salad dressing is a heterogeneous mixture, and table sugar (sucrose) is a compound.