What’s Inside a Bottle?

A portable container for holding liquids, usually with a narrow neck and mouth, made of glass or plastic. Often fitted with a teat for use in giving milk (or occasionally other liquids) to babies and young animals. Also called suck bottle.

Whether you’re heading to the office, out for a hike, or to your hot yoga class with your pup, an insulated bottle will help keep your drinks cold. Plus, reusable bottles help reduce the amount of single-use plastic we produce.

If you’ve ever blown across the top of a bottle, you probably heard a pleasant, resonant sound. That’s because the bottles are what is known as a closed-end air column, similar to the way clarinets and some organ pipes work. In this science activity, students will use bottles to investigate how the length of the column affects its pitch, and compare the pitches produced by their own bottles with those of classmates.

The majority of glass bottles are made from soda-lime glass—a mixture of about 6 percent lime (calcium oxide, or CaO), 4 percent magnesia (magnesium oxide, or MgO) and 2 percent alumina (aluminum oxide, or Al2O3). This type of glass is also used to make windows. It’s cheap to produce and easy to recycle, so it’s the primary glass used for bottles and other transparent containers.

Some bottles are made of polyethylene terephthalate (PET), or plastic, which is formed from the monomers ethylene glycol and terephthalic acid. It is lightweight and strong, with good water resistance, making it a popular choice for bottle manufacturing. In addition, PET is highly recyclable and has low levels of chemicals that may leach into beverages.

Other bottles are made of polycarbonate, which is made from bisphenol A (C15H16O2) and phosgene (COCl2). This plastic is more expensive than other plastics used for bottle production, but it has excellent chemical resistance, which makes it the preferred material for child-resistant bottles. It is also used for some laboratory bottles and for high-end reusable bottles.

Still other bottles are made of polypropylene, which is a thermoplastic resin that is made from a combination of four monomers—polyethylene (PE), propylene, and butane. This plastic has a wide range of application, but it is not as durable as PE or HDPE. Polypropylene is a good choice for storing and transporting acids or other volatile chemicals that require a tight seal. It is also a very safe plastic to use with children, because it will not break if dropped or crushed. Like all plastics, it should be stored in a cool place and out of the sun. This is especially important for bottled drinks, which can degrade in heat. This degradation can lead to toxic fumes that can be irritating to the lungs and eyes.