Like many restaurants in Austin, El Mercado serves margaritas both on the rocks (poured over cubes of ice) and frozen. We talked with a chemist at the University of Texas about the scientific differences between the two types of cocktails. Photo by Deborah Cannon for the Austin American-Statesman.

Have you ever wondered why rocks margaritas tasted more alcoholic than frozen margaritas? Or whether one had more overall ice and water than the other?

I was a chemistry nerd in high school, so thermodynamics is definitely something that’s popped into my head while sipping on a margarita on a patio somewhere in Austin. (Frozen in the summer months, rocks in the winter.)

After all these years of wondering, I reached out to a chemist at UT a few weeks ago, who happened to also be a huge margarita fanatic. (She has been known to travel with her blender, friends.)

Kate Biberdorf let me ask her all kinds of questions about ice shape and size, ethanol and heat, and her answers are in this story that is running in tomorrow’s paper.

I thought I’d highlight two of the Most Important Parts of that story, a base recipe for a frozen margarita and one meant for pouring over ice, aka “rocks.”

You’ll note that the rocks margarita has double the alcohol per serving. If you poured that much booze into a frozen margarita, all the ice crystals would melt even faster than they already do.

For more nerdy stuff like that, check out the main story.

For the recipes, from Austin’s David Alan and Joe Eiffler, authors of “Tipsy Texan” (Andrew McMeel, $19.99), scroll on down and get to shakin’ or blendin’.

Frozen Margarita

To make simple syrup, add 2 cups of sugar and 1 cup water to a saucepan. Heat and stir until the sugar has dissolved, then cool. If you don’t have a cocktail jigger, there are about two tablespoons in a fluid ounce.

2 oz. silver tequila
2 oz. Cointreau or Paula’s Texas Orange
2 1/2 oz. fresh lime juice
1 oz. simple syrup
Lime wedge for garnish

Combine the tequila, orange liqueur, lime juice and simple syrup in a blender cup and fill with ice until the ice is just covered by the liquid. Blend thoroughly (it may be necessary to add a little bit more ice to achieve the desired slushiness). Pour into a goblet, rimmed with coarse salt if you like, and garnish with a lime wedge. Serves 2.

On the Rocks Margarita

2 oz. silver tequila
3/4 oz. Cointreau or Paula’s Texas Orange
3/4 oz. freshly squeezed lime juice
1 tsp. (or bar spoon) simple syrup
Kosher salt, for the rim of the glass
Lime wedge, for garnish

Combine the tequila, orange liqueur, lime juice and simple syrup with ice in a cocktail shaker. Shake vigorously with the ice to properly chill and emulsify the ingredients. Strain into a salt-rimmed, chilled cocktail glass or onto fresh ice in a rocks glass or footed goblet. Garnish with the lime wedge. Serves 1.

— From “Tipsy Texan: Spirits and Cocktails from the Lone Star State” by David Alan (Andrew McMeel, $19.99)