Chew on this. Once you’ve taken care of your need for food, what else are you hungry for? Personally, I’m always hungry to learn, to share what I’ve learned, and to create. That’s why I’m a scientist and a writer. Maybe you are, too. The most exciting things to come out of science and creativity are those amazing “aha” moments—the triumphant feeling that comes when you just know you’ve “gotten it.” This book is the result of one such moment. A friend phoned me to suggest that we collaborate on a cookbook for kids. We both had young families at the time and cooked every day. I remember thinking to myself, “I don’t want to write a cookbook. I want to write about science for kids.” And then, the title Science Experiments You Can Eat popped into my head. There is nothing more amazing than having an idea pop into your head—especially when you know you can act on it. This “aha” moment gave me a vision for this book. I would use activities with food to help kids discover basic principles of science. I would create a tool so that you, too, could make discoveries and have many “aha” moments of your own.

Scientific discoveries have long influenced what shows up on your plate at mealtimes. Agronomy, the science of how food is grown, has helped farmers produce bigger and better crops. Methods of food preservation allow food storage for out-of-season consumption. Food additives and food packaging technologies, developed by scientists and engineers, maintain crispness, moistness, texture, flavor, visual appeal, and shelf life for thousands of different food products. There is virtually no chance of a famine in developed countries. That’s the good news.

The bad news is that the science of nutrition, which determines standards for a healthy diet, publishes new studies from time to time that tell us that a food we thought was good for us, or at least safe for consumption, can create health problems in the long run. Currently, 70 percent of the American diet is made up of processed food—food that has been manufactured to give it a longer shelf life and to make it taste “crave-able” so you can’t eat just one bite. Modern life is so hectic that many families don’t sit down together every evening to share dinner and conversation. One result of these changes is an obesity epidemic among children. So, in this new edition of Science Experiments You Can Eat, I have added a chapter about some of the influences of science on foods we do eat. It will help you read between the lines of the Nutrition Facts labels so that you understand the importance of healthy choices in your own diet. In addition, I have included nutrition information throughout the other chapters of the book as you also learn basic physics, chemistry, and biology.

But mostly this book is designed to whet your appetite for science. I want it to nourish your curiosity and feed your mind. I want to make science not only digestible but a feast of discovery. This book is a banquet of ideas and processes and yes, some very tasty and some not-so-tasty results. (Although I’ve done every experiment, to be honest, I haven’t eaten them all.) This is not gourmet dining, but it is food for thought.


Cookbooks give you precise directions for preparing food. Recipes are the result of many experiments in test kitchens that turn out predictable, delicious dishes. But this is a science book, not a cookbook. Food preparation produces a lot of changes in food. And change is what interests scientists.

There is no simpler activity for a cook than boiling water. Put water in a pot, put it over a burner on the stove, and wait for bubbles to form. But a scientist looks at this phenomenon and asks many questions: How hot does water have to be in order to boil? Does the temperature of water still rise after it starts boiling? If not, why not? Does water boil at a different temperature at sea level compared to in the mountains? If so, what does that tell us about this phenomenon? What is steam? How can steam be used to power, say, a locomotive? Scientific understanding of boiling water was one of the great breakthroughs in science and technology. The purpose of this book is to get you to think as a scientist. It will also help you as a cook. You will come to understand that science is not the mysterious process for eggheads it’s cracked up to be.

So when you do these experiments, keep an open mind. You’ll get ideas. You’ll start wondering. And, best of all, you may start asking questions that you can answer with experiments of your own. If that happens, you might just be on your way to one of those precious “aha” moments. So don’t dismiss the power of your own brain. Good questions are how science makes progress. Here’s what Einstein, the most amazing scientist of the twentieth century and the icon of “genius,” said about questions: “If I had an hour to solve a problem and my life depended on the solution, I would spend the first fifty-five minutes determining the proper question to ask, for once I know the proper question, I could solve the problem in less than five minutes.” And “To raise new questions, new possibilities, to regard old problems from a new angle requires creative imagination and marks real advances in science.”

The best way to get ideas is to do something. This book is a good place to begin. If you don’t get the results you expect, it is not a failure. Nature doesn’t lie. Your results depend on many variables—the equipment and ingredients you used and the procedures you followed. I’ve tried to give you directions in this book that will yield predictable results. But your kitchen is not my kitchen. If you don’t get the expected results, try to think of what factors might have caused the difference.

Redesign and repeat the procedure and see what happens. This is something scientists do—they publish their procedures so that others may repeat their experiments to make sure they all get the same data. In this way, science corrects itself. The body of knowledge that we call “science” is the result of countless experiments by many people. Imagine that! A community of people produced this knowledge and shared it with the world. Free! Science is the original wiki. Now you can join that community with experiments of your own.

Did you know scientists love to play? They’ve never forgotten what it’s like to be a kid. “Play” means that you suspend the rules and try stuff just for fun, just to see what happens. This book is your excuse to do just that.


The “stuff” that makes up food, you, and everything else in the universe is called matter. Chemists are scientists who study matter and how it changes. Matter is anything that has weight and takes up space.

When scientists first tackled the study of matter, they had to deal with the problem that matter in its natural state is complicated. Most matter exists mixed up with other matter. (Perhaps the most famous example of pure stuff is gold. It is called a “noble metal” because it doesn’t react with most other substances and is found pure in nature.) A solution, such as seawater, is an especially interesting kind of mixture. One amazing thing about a solution is that it is evenly mixed or homogeneous. In a pail of seawater, a cup taken from the top has exactly the same amount of salt in it as a cup taken from the bottom. Another amazing feature of solutions is that they become homogeneous all by themselves. No stirring is necessary.

Chemists have a way of thinking—a model—about solutions that accounts for their interesting properties. They say that solutions, like all matter, are made up of tiny particles too small to see. These particles are arranged in two phases. One phase is called the solvent. Water is the most common solvent around. The solvent phase is continuous. This means that the water particles are in contact with one another. The other phase is called the solute. Salt is a solute in seawater. The solute phase is discontinuous. Solute particles may occasionally bump into one another but for the most part they are surrounded by solvent particles. Salt water that you mix yourself in your kitchen is a simple solution, which means it has one solvent and one solute. But seawater has a number of solutes, including sodium bicarbonate (baking soda) and calcium carbonate (lime). A solution may be made of one or more solvents and one or more solutes.

When a solute dissolves, the solute particles move through the solvent in a process called diffusion. You don’t even have to stir. See for yourself. Drop a lump of sugar (a solute) into a glass of water (a solvent) and let it stand for a while. What happens to the lump of sugar? When you can no longer see any sugar crystals, taste the top of the solution with a straw. If sugar is present, you’ll taste it. Use the straw to taste the solution near the bottom of the glass. To do this, cover the top end of the straw with your finger before you lower the other end into the solution. When the bottom of the straw is where you want to take your sample, carefully flex your finger to let a small amount of the solution rise into the straw. Keep your finger on the top of the straw as you raise the bottom end of the straw to your mouth. Lift your finger to let the solution run into your mouth. With this technique you can taste samples from all parts of the solution. But be careful to keep the disturbance to the solution as little as possible when you insert the straw. Is the solution homogeneous? If it isn’t, wait awhile and taste again.

Solutions are important in the study of matter. You can often discover what a substance is by the solvent it dissolves in and by how much of it dissolves. Many chemical reactions take place in solutions that will not take place in air. Life is only possible because of solutions. The human body is 50 to 75 percent water, and most of the chemical reactions in your body take place in solution. This chapter will introduce you to some different solutions and some of the ways solutions are used to learn about matter.

Written by Vicki Cobb in "Science Experiments You Can Eat", Harper, an imprint of HarperCollins Publisher, New York, USA, 2016, excerpts chapter 1 & 2. Digitized, adapted and illustrated to be posted by Leopoldo Costa.