Density and Alchohol

Density is an important concept to understand when you are trying to figure out if something will float or sink, but it can also affect the gas in our atmosphere and even liquids in mixed drinks!

Layered drinks look very impressive, but it’s really simple science that makes it all possible. The layers are able to float on one another because of specific gravity. Specific gravity is the ratio between the density of a substance and a reference standard. Usually we use water as a standard for liquid, which has a specific gravity of 1.00. If oil has a specific gravity of 0.914 and we add it to water, it will float on the water because its specific gravity is less than that of water.


Photo courtesy of Pete:

The same concept can be applied to mixed drinks. In general, liquids with a higher sugar content like grenadine, liqueurs and brandies have a higher specific gravity, which means that they would sink in water. Liquids with higher alcohol content like vodka, absinthe and Everclear™ tend to have a lower specific gravity, which means they would float on water. In actuality, alcohol and water have the tendency to mix together, but alcohol can float on water if poured very carefully over the back of a spoon onto the water. Bartenders use the concept of density and specific gravity to create layered mixed drinks!

A simple layered drink to make is a Dark ‘n Stormy. There are only two ingredients, so it’s an easy one for a beginner.

1. Start with an old fashioned glass filled with ice.
2. Pour in about 4 fluid ounces of ginger beer.
3. Carefully pour in about 2 fluid ounces of dark rum. It may be easier to slowly pour it over the back of a spoon.
4. Done!
It is easier to make layered drinks containing alcohol because alcohol has a lower specific gravity than most liquids. If you are interested in non-alcoholic layered drink, consider making this fruity beverage!
1. Choose any glass you’d like. The narrower the better because you can see the layers better.
2. Start with a splash (or 2) of grenadine at the bottom.
3. Mix 1 part orange juice and 1 part pineapple juice together in a separate glass.
4. Carefully pour the orange-pineapple juice mixture over the back of a spoon onto the grenadine.
5. Then, enjoy!

These drinks look great without a lot of work. Just science! To see density in action, visit OKRA Charity Saloon on Cocktail Chemistry Mondays (September 19th) and vote for HMNS while you are there!


‘Shaken, not stirred’ is more bond than you think!

Since HMNS is one of the featured charities at Okra Charity Saloon in September (read about it here), we’re doing a series of blog posts about cocktail chemistry this month. Get to know your drinks on a more molecular level. We’ll explore acids and bases, surface area, density, and fluorescence. It’s going to be elemental.



Photo Couresy of Didriks

It’s the signature drink of Sir Ian Fleming’s James Bond: dry vodka martini, shaken, not stirred.

Vodka must be at least 40% alcohol by volume (ABV) to actually be called “vodka” in the United States, according to the standards of identity section of U.S. federal codes. Since most traditional vodkas are almost entirely ethanol and water, that means for every liter of vodka, a whopping 400 milliliters are ethanol.

The vodka martini is six parts vodka, one part dry vermouth; garnishes can range far and wide, from an olive to a lemon peel (a “twist”). Most of the flavor of the martini comes from the vermouth‒specifically the ester chains that are part of the overall organic compound.
An ester is a chemical compound that begins as a carboxylic acid, which looks like this:



In this diagram, a carbon atom is double-bonded with an oxygen atom, single-bonded with a hydroxyl group (OH), and single-bonded with the rest of the atomic chain (R). This pattern is what is defined as a carboxylic acid.

To become an ester, the hydrogen atom in the hydroxyl group must be replaced with something else, like more carbon atoms:



In this diagram, a carbon atom is double-bonded with an oxygen atom, single-bonded with an oxygen atom that is bonded to another compound, and single-bonded to yet another compound. This is the definition of an ester.

Before the martini is served, it is mixed with ice, and this ice serves two purposes. First, it’s important to note that chemically, ice is just H2O. When H2O is added to an ester, the ester starts to become more polarized and saturates out into what is called a micelle. In this context, the micelle is a tiny drop of esters clustered in one spot (micelles are also used in things like laundry detergent and medication, but more on that another time). Cooling the martini down releases the esters from the micelle and adds flavor to the drink. Luckily enough, ice is also pretty cold.


Photo courtesy of rick

So why get your martini shaken, not stirred? Shaking the cocktail with ice lowers the temperature more effectively than stirring with ice does, producing better flavor! Shaking a liquid is inherently more violent than stirring it. As a result, the individual molecules are bouncing around much more quickly when shaken. When the molecules are moving quickly, the liquid is covering more ground and has more inherent surface area. And since ice melts from the outside in, greater surface area of the liquid means greater contact with the melting ice, which will cool the drink down more quickly.

The flipside of cooling the drink down more quickly is that, as the ice melts, it waters down the drink. Stirring a martini gives it a slightly higher ABV, as there will be less melted water when the cocktail is poured into a chilled glass. But doing so sacrifices the flavor of the esters, something not even James Bond was willing to do.

Stop by Okra Charity Saloon to try a vodka martini, shaken, not stirred, during the month of September, and support your Museum! Don’t forget to check back next week when we discover density differences in beverages.

Cocktail Chemistry: A Balancing Act

Since HMNS is one of the featured charities at Okra Charity Saloon in September (read about it here), we’re doing a series of blog posts about cocktail chemistry this month. Get to know your drinks on a more molecular level. We’ll explore acids and bases, surface area, density, and fluorescence. It’s going to be elemental.

Life is all about balance. Sorry, did I say life? I meant cocktails. As any experienced bartender will tell you, concocting the perfect drink has everything to do with balance. Bartenders are charged with making sure the basic components of their drinks will play well together in the glass and dance on your taste buds. Understanding and balancing flavors is a critical part of being a cocktail chemist.
When you’re talking about the fundamentals of chemistry, you turn to the periodic table.



Every element is neatly organized and laid out according to their atomic number, electron configurations, and chemical properties. There are currently 118 elements that make up our entire universe. The periodic table of cocktail chemistry would look a little different, a little more basic (not literally). Instead of 118 elements, the world of cocktail chemistry has only four: alcohol, sugar, acidity, and bitterness. We’re going to focus on the acidity element.

Let’s revisit high school chemistry for a moment with Acids and Bases: 101. When molecules break down in water, some release hydrogen ions (H+), while others release hydroxide ions (OH-). The pH scale measures the concentration of these hydrogen ions and hydroxide ions and tells us how acidic or basic a liquid is. Acids fall between 0 and 7, and bases fall between 7 and 14. The more acidic a liquid is, the lower its pH; the more basic a liquid is, the higher its pH. When acids and bases are mixed, they react with one another in what’s called a neutralization reaction. Think back to when you made your first science fair volcano. The combination of baking soda and vinegar was an explosive, bubbling demonstration of an acid-base reaction.

When we’re talking about cocktail chemistry, we’re more concerned with the way these solutions taste. Acids are characteristically sour, while bases are bitter. Remember the whole balance thing? This is where it comes into play.

Bartenders typically rely on the citrus genus for the acidic component of a cocktail. Oranges, lemons, limes, and grapefruit are frequently used to counteract the sugars and bitters in their concoctions. Understanding the chemical composition of these citric elements is critical.


cocktail 2

Lemons and limes are the most acidic with a pH between 2.0-2.6. Limes have slightly less sugar than lemons. This is why lemons pair well with gins and rye whiskies, while limes pair well with rum and tequila. Grapefruit and orange both have a higher sugar content and slightly lower pH than their citrus cousins. With this knowledge, you can figure how much citric acid you need to counteract the sugar in a cocktail. Since grapefruit and orange have an inherently higher sugar content, they don’t require as much sugar to counter their acidity. Not too sweet, not too sour. You can use science to make sure it’s just right.
Chemists have also found that acids help the flavors of a cocktail combine more evenly, so each sip contains the full flavors of the drink. (We’ll talk more about density and separation of liquids in one of our upcoming cocktail chemistry blog posts, but there’s no separation here!)

If you’re looking to try out a few acidic cocktails, try ordering sours, smashes, or any citric-based drink. Here are a few of my favorites:

1) Screwdriver: A classic combination of orange juice and vodka. Since orange has a high sugar content compared to its acidity, it acts as both the sugar and acid. Paired with vodka, this is a simple, refreshing drink.
2) Lemon drop martini: Lemon drops use fresh lemon juice for a strong, tart acidic component. The intense acidity is balanced with simple syrup and triple sec. These flavors pair well with vodka for a crisp, refined cocktail.

cocktail 3

3) Paloma: This drink balances two acidic components with both grapefruit juice and lime juice. Since limes have an extremely low sugar content, palomas contain additional sugar or simple syrup to balance their intense tartness. This combination goes perfectly with mescal or tequila. It’s topped off with club soda for a cool, bubbly finish.


Stop by Okra Charity Saloon to try one of these acidic cocktails during the month of September, and support your Museum! Don’t forget to check back next week when we explore the surface area of cocktails.

51: More than just a number.

by Kaylee Gund

What’s in a number? They’re symbols we use to quantify the world around us, the basis for astrophysics and time measurement, and among the first things we learn in language.

5: right angle meets curve.

1: straight as a ruler.

Using some mental glue, stick these together and the result is 51, a random number, multiple of seventeen and three, a discrete semi-prime, and the whimsical subject of this blog entry. While probably not in the forefront of your conscious mind, the number 51 has more than a few significant meanings for the Houston Museum of Natural Science, enumerated below (pun intended).

  1. Years

Fifty-one years ago, the original Burke Baker Planetarium was built. The very first venue at the current HMNS, the Planetarium featured cutting-edge projector technology and quite literally made the nation see stars.


The Planetarium closed Dec. 21, 2015 for a complete renovation, but will return better and sharper this March with cutting-edge optics, cloud-enabled digital projection technology, and more seating. Stay tuned to this blog and social media for updates on this exciting project!

  1. Telephone codes

Calling Peru? Dial 51.


Luckily, a visit to South America can be arranged without costly international phone calls. Climb Mayan temple ruins, hear ancient fables come to life, and see one-of-a-kind artifacts in the John P. McGovern Hall of the Americas, a world hidden away on the third floor of the Museum.

  1. Electrons

Antimony (Sb): a soft, lustrous metal element, atomic number 51.


Despite being relatively rare on its own, antimony can be found in mineral form with sulfur, a compound called stibnite. A huge sample of stibnite can be found in the Cullen Hall of Gems and Minerals, looking more like a shiny porcupine than anything else, but stibnite was also used by ancient Egyptians. The poisonous qualities of antimony made it useful as a component of ancient eyeliner, as described in the Hall of Ancient Egypt. Painting the eyelids with a mild toxin made bacterial eye infections, a constant threat in the marshes of the Nile, much less likely to occur.

  1. Genetic breakthroughs

In 1952, the double helix structure of DNA was deduced with the help of an x-ray crystallography image called Photo 51.


Often featured in school textbooks, the pivotal Photo 51, to the untrained eye, bears little resemblance to the 3-dimensional twisted ladder models of DNA, but visitors can always measure up against the enormous 3D model of our genetic material in the Welch Hall of Chemistry instead.

  1. Secrets

What happens in Area 51 stays in Area 51… the same could be said for the Museum’s offsite collections storage facility.


Holding millions of artifacts and specimens, the facility is full of treasures never before on display. For those select few who want to delve deeper into the secrets of HMNS, limited behind-the-scenes tours are available – if you dare!


Editor’s Note: Kaylee is the Project Manager/Data Analyst for Business Development and Budget at the Houston Museum of Natural Science.