Why so many types of alcohol?

You've probably seen many terms for alcohols listed on the labels of products around the house. Most of the alcohols are not used on their own. The one that's for consumption, ethyl alcohol -- also called ethanol or grain alcohol -- is used in beer, wine, and liquor, and is often made by fermenting sugar and yeast. Ethyl alcohol can also be produced synthetically, in which case it is not used in beverages but is frequently found in hand sanitizers and perfumes.

Denatured alcohol is simply ethyl alcohol that has been mixed with toxic or nauseating substances, called denaturants (these prevent the alcohol from being consumed). This type of alcohol is used in cleaning and stain removal products, among others.

Isopropyl alcohol, or isopropanol, is made from propylene gas. It shares many properties with synthetic ethyl alcohol. It is poisonous if consumed. You'll find it in the household products, including windshield washer fluids and nail-polish remover. One of the most common is rubbing alcohol, which usually consists of isopropyl alcohol diluted in water.

Why do my cakes fall in the center?

Sometimes the oven is too hot: The outside of the cake cooks more quickly than the middle, which falls because it is underdone. If the oven is too cool, the results can be uneven as well. Use an oven thermometer to see if your appliance's settings are accurate. And always check cakes for doneness with a toothpick.

Measure ingredients accurately, and never substitute one ingredient for another without making adjustments. This is most important when using baking powder and baking soda. When mixed into batter, these chemical leaveners produce carbon dioxide, which makes tiny bubbles in batter expand and rise, adding volume and lightening the cake. Too much or too little of either can result in a cake that does not rise properly.

Check the expiration date on baking powder and baking soda before using them. Even better, mark the date of purchase on these products and replace them twice a year.

Adapted from Martha Stewart Living Magazine. Questions should be addressed to Ask Martha, care of Letters Department, Martha Stewart Living, 11 W. 42nd Street, New York, N.Y., 10036. Questions may also be sent by electronic mail to: mslletters@marthastewart.com. Please include your name, address, and daytime telephone number. Martha Stewart regrets that unpublished letters cannot be answered individually.