Book 9 activities
Try it at home: 150 science activities from Book 9
Every question in A Million Whys Book 9, The Food Expedition, ends with a "Think like a scientist" idea. Here they are in one place. Each one links to its question page, with the video and the full answer.
Expedition 1: Kitchen Chemistry (25)
1. Why Are Ice Cubes Cloudy in the Middle?
Freeze one tray of tap water, and another of boiled-then-cooled water (a grown-up does the boiling), and compare how clear the cubes are.
Do this with a grown-up2. Why Does Ice Cream in a Bag Need Salty Ice?
With a grown-up, shake cream, sugar, and vanilla in a small zip bag. Set it inside a bigger bag of ice and salt. Wear mittens and keep shaking. Do not taste the salty ice, only the ice cream.
Do this with a grown-up3. Why Does Mayonnaise Stay Creamy When Oil and Water Usually Split?
Shake oil and vinegar in a jar, then add a spoonful of mustard and shake again. Which stays mixed longer? Never taste raw egg mixtures.
4. Why Does Pepper Run Away From a Drop of Dish Soap?
Sprinkle pepper on a bowl of water, then touch the surface with a soapy fingertip.
5. Why Does Sugar Stop Dissolving If You Keep Adding It?
Stir spoonfuls of sugar into a glass of room-temperature water until it stops dissolving, and count the spoons. Never taste hot drinks; wait until they are warm.
6. Why Does Hot Cocoa Form a Skin on Top?
Let a grown-up pour a mug of cocoa and wait until it is only warm, not hot. Then look at the skin on top, and never taste hot cocoa.
Do this with a grown-up7. Why Does a Drop of Water Make Hot Oil Spit and Pop?
Ask a grown-up to show you, from a safe distance, how they pat food dry before it goes into hot oil.
Do this with a grown-up8. Why Does Lemon Juice Taste So Sour?
With a grown-up's okay, try a tiny bit of lemon, orange, and apple. Rate each sourness from 1 to 5. Which one is the sourest? Skip anything you are allergic to.
Do this with a grown-up9. Why Does the Fizzy Mix of Baking Soda and Vinegar Get Cold?
With a grown-up, mix two tablespoons of baking soda with half a cup of vinegar in a cup in the sink, and feel the outside of the cup. Do not taste it.
Do this with a grown-up10. Why Does a Hard-Boiled Egg Get a Green-Gray Ring Around the Yolk?
With a grown-up, boil one egg for 10 minutes and another for 15, cool both in cold water, and cut them open to compare.
Do this with a grown-up11. Why Does Metal Feel Colder than Wood in the Same Room?
Touch a spoon and a wooden spoon from the same drawer.
12. Why Do Tiny Bubbles Cling to the Pot Before the Water Boils?
With a grown-up watching a pot (kids stay back from the steam), note when the first tiny bubbles appear and when big rolling bubbles begin.
Do this with a grown-up13. Why Does Pasta Water Get Cloudy?
Ask a grown-up to save a cup of pasta water (it is very hot) for the sauce next dinner.
Do this with a grown-up14. Why Does Honey Turn Grainy and Hard in the Jar?
Ask a grown-up to set a jar of crystallized honey in a bowl of warm (not hot) water and watch the crystals melt away.
Do this with a grown-up15. Why Do Some Candies Feel Cold When They Dissolve?
Notice mint gum’s cool tingle with no ice present.
16. Why Does Bread Get Stale Even If It Isn’t Moldy?
With a grown-up, toast stale bread and notice how heat can refresh the texture a bit.
Do this with a grown-up17. Why Does Gelatin Turn Liquid Into Wobbly Solid?
Make gelatin with a grown-up, who handles the hot water, and tip the mold once it is set.
Do this with a grown-up18. Why Do Fizzy Drinks Go Flat?
With a grown-up, pour the same fizzy drink into two cups, one cold and one room temperature, and watch which goes flat first. Never shake a bottle.
Do this with a grown-up19. Why Does Whipping Cream Become Fluffy?
With a grown-up whisking, watch the cream stages: frothy, then soft peaks, then stiff peaks.
Do this with a grown-up20. Why Does Lemon Juice Keep Cut Apples From Browning?
With a grown-up slicing, brush lemon juice on half an apple slice. Leave the other half plain. Wait one hour and compare them. Check for allergies before you taste.
Do this with a grown-up21. Why Do Microwaved Foods Have Hot and Cold Spots?
With a grown-up, heat leftovers in a microwave-safe bowl, stir halfway, and let them stand before tasting. Steam can burn, so a grown-up opens lids away from faces.
Do this with a grown-up22. Why Does an Old Egg Float in Water?
With a grown-up, gently lower a fresh egg and an older egg into two glasses of water and compare. Wash your hands after touching raw eggs.
Do this with a grown-up23. Why Does Salt Make Food Taste More ‘Alive’?
With a grown-up, taste unsalted and lightly salted tomato slices (check for allergies first).
Do this with a grown-up24. Why Does Yeast Need Sugar or Starch?
With a grown-up, mix warm, not hot, water with sugar and yeast. Watch the foam grow over the next few minutes. Do not taste it. What do you think is making the foam?
Do this with a grown-up25. Why Is Kitchen Chemistry Safe Science When You’re Careful?
Pick one sink experiment and list two safety rules first.
Expedition 2: Taste, Smell & Cravings (25)
26. Why Does Food Need Smell to Taste ‘Complete’?
With a grown-up's okay, taste a jelly bean with your nose pinched. Then taste another with your nose unpinched. Which one has more flavor? Check for allergies first.
Do this with a grown-up27. Why Is the ‘Tongue Map’ a Myth?
Touch sugar water to tip and side , both can taste sweet.
28. Why Does Milk Calm a Spicy Mouth Better than Water?
With a grown-up, after a mild spicy bite, compare how a sip of milk and a sip of water feel (skip it if you don’t like spicy foods).
Do this with a grown-up29. Why Does Cold Water Feel Icier After You Eat Mint?
Sip room-temperature water and notice how it feels. Then chew a mint, with a grown-up's okay. Sip the water again and compare. Skip it if you have allergies.
Do this with a grown-up30. Why Do Cravings Happen?
Pause 10 minutes before a craving snack , notice if it fades.
31. Why Does Hunger Make Food Smell Stronger?
Sniff dinner prep before and after a meal , compare intensity.
32. Why Is Umami Called the Fifth Taste?
Step two: a scientist names umami. In 1908, Japanese scientist Kikunae Ikeda found the savory taste in seaweed broth. He called it umami, which means delicious taste in Japanese, and later scientists found real sensors for it.
33. Why Do Some People Dislike Bitter Greens?
With a grown-up roasting it, try roasted and raw broccoli and notice how heat changes the flavor.
Do this with a grown-up34. Why Does Orange Juice Taste Weird After Toothpaste?
Brush, wait, then juice , or juice first next time.
35. Why Do Fizzy Drinks Tingle?
Compare flat and fizzy versions of the same soda.
36. Why Can the Smell of One Food Make You Feel Queasy Years Later?
Ask a grown-up about a food smell that bothers them and one they love. Can they remember why?
Do this with a grown-up37. Why Does Food Taste Blander on an Airplane?
Ask a grown-up who has flown whether meals tasted different up high, and what they noticed.
Do this with a grown-up38. Why Do Companies Design ‘Crunch’?
Eat a crunchy snack with your ears covered by your hands, then uncovered. Does the crunch seem different? Keep sounds quiet to protect your ears.
39. Why Does Sweetness Make You Smile?
Find natural sweetness in fruit and in candy, and compare the two.
40. Why Do Pickles Taste Sour and Salty Together?
With a grown-up, taste one small bite of pickle, then smell (don’t sip) a spoonful of vinegar. Compare what you notice.
Do this with a grown-up41. Why Does Smelling Food Make Your Mouth Water?
Walk past bakery vents and notice the saliva cue.
42. Why Do Some Smells Seem ‘Loud’ Even in Tiny Amounts?
With a grown-up, open a bottle of vanilla and sniff, never sip, to notice how little you need.
Do this with a grown-up43. Why Does Temperature Change Flavor?
With a grown-up’s okay, taste chocolate cool and slightly warm, never hot (check for allergies first).
Do this with a grown-up44. Why Do Kids’ Favorites Differ From Grown-Ups’?
Try one new veggie three different ways this month.
45. Why Is Your Tongue Covered in Tiny Bumps?
Use a mirror to look at the bumps on your tongue, and notice the small pink dots near the tip.
46. Why Can the Color of a Plate Change How Food Tastes?
Serve the same snack on a white plate and a colored plate, then ask a friend which tastes better.
47. Why Does Salt on Caramel or Chocolate Work?
With a grown-up’s okay, taste dark chocolate with a tiny salt flake and notice the change (check for allergies first).
Do this with a grown-up48. Why Do You Get Tired of One Candy Flavor?
Alternate two snacks and notice longer interest.
49. Why Does Smelling Vanilla Make Things Seem Sweeter?
With a grown-up’s okay, smell vanilla while tasting plain milk. Does it seem sweeter? (Check for dairy allergies first.)
Do this with a grown-up50. Why Is Mindful Tasting a Superpower?
Sit down and eat one raisin in 30 slow seconds, then list five sensations (check for allergies first).
Expedition 3: Bread, Bubbles & Baking (25)
51. Why Do Bakers Let Dough ‘Proof’ Before Baking?
On a grown-up bake day, mark the bowl with tape at the dough’s starting height and check it every 30 minutes.
Do this with a grown-up52. Why Do Bakers Knead Dough?
On a grown-up bake day, compare a kneaded ball with a barely mixed lump.
Do this with a grown-up53. Why Does Gluten Matter in Wheat Bread?
Wash a flour dough ball under water (grown-up) to feel leftover gluten gum.
Do this with a grown-up54. Why Do Some People Need Gluten-Free Bread?
Read a gluten-free label together and spot alternate flours.
55. Why Do Some Recipes Need Both Baking Soda and Baking Powder?
Compare two recipes, one with baking soda and one with baking powder, and spot acid ingredients like buttermilk, yogurt, or honey.
56. Why Must Oven Spring Happen Fast?
Watch muffins through the oven window or light (no door opening!) at minute 5 and minute 15, from a safe distance.
Do this with a grown-up57. Why Are Some Cookies Chewy and Others Crispy?
On a grown-up bake day, bake two batches, one for two minutes less, and compare them once they are fully cool.
Do this with a grown-up58. Why Do Cooks Pat Food Dry Before Browning It?
With a grown-up at the pan, toast two bread slices, one dry and one lightly dampened, and compare the browning.
Do this with a grown-up59. Why Does Caramel Need Careful Heat?
Watch sugar melt with a grown-up , never touch molten sugar.
Do this with a grown-up60. Why Does Steam Help Some Bread Crusts?
Watch a grown-up add a small pan of hot water to a hot oven to make steam. Kids stay back , steam burns.
Do this with a grown-up61. Why Do Pancakes Make Bubbles That ‘Tell You’ to Flip?
Count the bubble pops before the grown-up flips the next pancake.
Do this with a grown-up62. Why Does Sourdough Smell Tangy?
Sniff sourdough starter in a closed jar and then commercial yeast dough, and compare.
63. Why Rest Cookie Dough in the Fridge?
Bake one cookie now and one tomorrow from the same dough.
Do this with a grown-up64. Why Do Muffins Get Tunnels If You Mix Too Much?
With a grown-up baking, mix one batch until smooth and one only until just combined, then compare the muffins.
Do this with a grown-up65. Why Does Pie Dough Like Cold Butter?
Feel grated cold butter and soft butter, and notice how they would make different pie crusts.
66. Why Can a Slammed Oven Door Make a Cake Fall?
Watch how a grown-up closes the oven door gently on bake day.
Do this with a grown-up67. Why Measure Flour Carefully?
Weigh one ‘cup’ of flour scooped and one spooned, and see the gram gap.
68. Why Does Yeast Need Warm Water, Not Hot?
With a grown-up, use a thermometer to check that the water is about 40 to 45°C (105 to 115°F), as warm as a cozy bath.
Do this with a grown-up69. Why Do Bagels Get Boiled Before Baking?
Compare a bagel’s chew with a soft dinner roll.
70. Why Does Laminated Dough Make Croissants Flaky?
Count visible layers in a torn croissant.
71. Why Do Ovens Have Hot Spots?
After a batch of cookies has cooled, map which corners of the tray browned most.
Do this with a grown-up72. Why Does Altitude Change Baking Recipes?
If you live high up, find one local baking tweak tip.
73. Why Do We Grease or Paper Pans?
Compare one muffin baked in a paper liner with one in a bare tin cup (a grown-up handles the hot pans).
Do this with a grown-up74. Why Does Bread Sing When It Cools?
When a grown-up sets a fresh loaf on a rack, listen from a hand’s width away to hear the crackle.
Do this with a grown-up75. Why Is Sharing Baked Bread a Science Celebration?
Teach a friend one bread ‘why’ while you snack.
Expedition 4: Fruits, Veggies & Plants We Eat (25)
76. Why Are Fruits Often Sweet When Ripe?
Compare the sweetness of a green banana and a ripe one.
77. Why Do Bananas Ripen in a Bag Faster?
Bag-ripen one banana; leave one out; compare next day.
78. Why Is a Tomato a Fruit to Scientists?
List three ‘veggie’ foods that are botanical fruits.
79. Why Do Leafy Greens Wilt in the Fridge?
Revive wilted lettuce in ice water for 10 minutes.
80. Why Are Carrots Orange?
Spot orange and yellow carotene colors in carrots, sweet potatoes, and pumpkin.
81. Why Do Carrots Taste Sweeter After a Frost?
Ask a grower about fall carrot sweetness.
82. Why Soak Beans Before Cooking?
Weigh dry beans, then soaked beans, and see the water gain. Never eat them raw; a grown-up cooks them thoroughly.
Do this with a grown-up83. Why Do Apples Float?
Test an apple and a potato in a sink of clean water and see which floats.
84. Why Are Chili Peppers Spicy for Mammals But Not Birds?
Look up wild chili seed dispersal by birds.
85. Why Do Onions and Garlic Make Savory Magic?
Sniff whole garlic and then crushed garlic (a grown-up crushes it) and notice the aroma jump.
Do this with a grown-up86. Why Is Fiber in Plants Helpful?
Choose an apple with the skin on, and peel another, and think about the fiber difference.
87. Why Do Potatoes Turn Green in Light?
With a grown-up, look for green patches or sprouts on pantry potatoes (look, don’t taste).
Do this with a grown-up88. Why Sprout Seeds on a Windowsill?
Sprout a few bean seeds in a wet paper towel bag, and just watch them grow. Raw sprouts can carry germs, so don’t eat them.
89. Why Are Berries Often Tiny and Many?
Count the seeds in a strawberry and in an avocado.
90. Why Do Dried Lentils Cook Faster than Dried Chickpeas?
Compare package cook times on two legumes.
Do this with a grown-up91. Why Do Herbs Smell Strong When Rubbed?
Rub basil gently and inhale.
92. Why Is Corn a Seed, a Grain, and a Vegetable Depending on Talk?
List corn’s roles on the cob, in popcorn, and in a tortilla.
93. Why Do Cucumbers Feel Cool?
Compare a fridge-cold cucumber with a room-temperature one.
94. Why Ferment Cabbage Into Sauerkraut?
With a grown-up’s okay, taste sauerkraut and raw cabbage and notice the acid difference (check for allergies first).
Do this with a grown-up95. Why Are Mushrooms Neither Fruits Nor Veggies Exactly?
With a grown-up, look at the gills under the cap of a store-bought mushroom. Never taste or pick wild mushrooms.
Do this with a grown-up96. Why Blanch Veggies Before Freezing?
Ask why frozen peas stay so green.
97. Why Do Citrus Peels Smell Stronger than the Juicy Insides?
A grown-up grates orange zest, and you sniff it, being careful of the sharp grater.
Do this with a grown-up98. Why Rotate Crops on Farms?
Draw a three-year crop rotation cartoon.
99. Why Does Red Cabbage Juice Change Color with Lemon or Baking Soda?
With a grown-up, steep chopped red cabbage in warm water, strain it, and add a drop of lemon juice to one cup and a pinch of baking soda to another. Don’t drink the mixtures.
Do this with a grown-up100. Why Thank Plants at Dinner?
Say one plant part you ate: root, leaf, fruit, or seed.
Expedition 5: From Farm to Plate (25)
101. Why Do Farms Use Soil So Carefully?
With a grown-up, dig up a small scoop of garden soil with a trowel and look for worms. Put them back gently!
Do this with a grown-up102. Why Irrigate Fields?
Compare drip irrigation and sprinklers, and decide which wastes less water.
103. Why Do Bees Matter for So Many Foods?
List five foods that need pollinators, such as almonds and apples.
104. Why Harvest at Peak Ripeness for Some Crops?
With a grown-up’s okay, taste a just-ripe strawberry and an underripe one.
Do this with a grown-up105. Why Do Farms and Stores Chill Milk and Meat Quickly?
With a grown-up, put the same amount of warm (not hot) water in two cups, one in the fridge and one on the counter, and check each with a thermometer after 30 minutes.
Do this with a grown-up106. Why Pasteurize Milk?
Read a milk carton for ‘pasteurized’ wording.
107. Why Do Eggs Have Dates on Cartons?
Find pack and best-by dates on your eggs.
108. Why Truck, Ship, and Fly Food Around the World?
Check stickers: where was this apple grown?
109. Why Do ‘Food Miles’ Matter to Some Families?
Plan a mostly-local snack from your region.
110. Why Package Foods in Different Materials?
Sort recycling from one grocery haul with a grown-up.
Do this with a grown-up111. Why Do People Can Food in Jars and Cans?
Compare canned corn and fresh corn textures with a grown-up (use food from sealed, undamaged cans).
Do this with a grown-up112. Why Freeze Vegetables?
Check freezer burn on an old bag , ice crystals clue.
113. Why Do Grocery Stores Mist Veggies?
Notice which produce gets misted and which stays dry.
114. Why Are Grocery Stores Laid Out the Way They Are?
Time a scavenger hunt for three ingredients.
115. Why Do Bakers Start Before Dawn?
Ask a bakery what time dough mixing begins.
116. Why Does a Package Say ‘May Contain Traces of Nuts’?
With a grown-up, find a ‘may contain’ line on a snack package and notice what it warns about.
Do this with a grown-up117. Why Refrigerate Leftovers Promptly?
After dinner, set a timer to remind a grown-up. Leftovers go in the fridge within two hours. Be a kitchen safety detective! Be a kitchen safety detective!
Do this with a grown-up118. Why Compost Food Scraps?
Start a small counter scrap bowl for compost if you have access.
119. Why Do Farmers Markets Feel Different From Megastores?
Ask one vendor how they grew or made their item.
120. Why Is Food Waste a Big Deal?
Plan meals to use one ‘must eat soon’ item.
121. Why Do Nutrition Labels List Serving Sizes?
Pour your usual cereal, then check the listed serving.
122. Why Wash Produce Even If You’ll Peel It?
With a grown-up slicing, wash a cucumber before you cut it for your next snack.
Do this with a grown-up123. Why Do Some Fish Need Cold Trucks More than Apples?
Notice seafood on ice at the store , why the bed of ice?
124. Why Celebrate Cultural Foods?
Cook a family recipe and ask who taught it.
Do this with a grown-up125. Why Say Thanks Along the Food Chain?
Name five jobs that helped today’s lunch exist.
Expedition 6: Food Detectives & Kitchen Safety (25)
126. Why Wash Hands Again After Touching Raw Eggs or Meat?
Sing a 20-second wash song every cook session, especially after touching raw eggs or meat.
Do this with a grown-up127. Why Use Separate Boards for Raw Meat and Veggies?
Label two boards: ‘raw protein’ and ‘ready-to-eat.’
128. Why Cook Burgers to a Safe Temperature?
Watch a grown-up use a meat thermometer once, and ask them to show you the safe temperature.
Do this with a grown-up129. Why Thaw Meat in the Fridge, Not on the Counter?
Plan ahead: with a grown-up, move frozen meat to the fridge the night before. Never thaw it on the counter.
Do this with a grown-up130. Why Isn’t a Sniff Test Enough to Tell If Food Is Safe?
When you are unsure about a food, ask a grown-up. When in doubt, throw it out.
Do this with a grown-up131. Why Keep the Fridge at About 4°C (40°F)?
Check your fridge thermometer this week.
132. Why Should We Throw Out Jars with Bulging Lids?
Inspect pantry cans for dents, rust, or swelling with a grown-up.
Do this with a grown-up133. Why Tie Hair Back in the Kitchen?
Add a kitchen hair band to your cooking kit.
Do this with a grown-up134. Why Wipe Spills Right Away?
Keep a dedicated spill cloth in a known spot.
135. Why Read Recipe Steps Fully First?
Highlight tools and times before you start.
136. Why Measure with the Right Tools?
Find a liquid measuring cup with a pour spout at home.
137. Why Taste with a Clean Spoon Each Time?
Set a ‘tasting spoon park’ plate beside the stove.
Do this with a grown-up138. Why Be Careful with Raw Cookie Dough?
With a grown-up, find a no-bake dough recipe and check that it uses heat-treated flour and no raw egg. Never taste raw dough.
Do this with a grown-up139. Why Store Cleaning Sprays Away From Food?
With a grown-up, check where cleaning sprays live, and make sure they are away from food and out of little kids’ reach.
Do this with a grown-up140. Why Use Oven Mitts with No Wet Spots?
Check mitts for thin worn patches before bake day.
141. Why Are Some Foods Choking Hazards?
Practice slow, mindful chewing at your next snack, and ask a grown-up about a first-aid course.
Do this with a grown-up142. Why Does Raw Meat Go on the Bottom Shelf of the Fridge?
With a grown-up, look at the shelves in your fridge and decide where raw meat should go.
Do this with a grown-up143. Why Keep Pets Off Kitchen Counters?
Make a pet-free rule for the counters, and wash your hands after petting animals.
144. Why Cool Big Soups in Shallow Pans?
With a grown-up, split a big batch of hot soup into two shallow containers, and let them cool before covering and chilling.
Do this with a grown-up145. Why Check for Food Recalls?
Show a grown-up how to check an official recall site.
Do this with a grown-up146. Why Adapt Recipes for Allergies Politely?
Practice asking, ‘Does this contain nuts or dairy?’, before sharing a treat.
147. Why Should You Get Out and Tell a Grown-Up If a Fire Starts in the Kitchen?
Walk through your family’s fire escape plan and find the smoke alarm and the exits. Fire extinguishers are for grown-ups.
Do this with a grown-up148. Why Should You Change Only One Thing at a Time When You Tweak a Recipe?
With a grown-up, pick a recipe and change just one ingredient, like a little less sugar, and write down how it turned out.
Do this with a grown-up149. Why Teach Younger Siblings Kitchen Rules?
Demo a perfect handwash for someone younger.
150. Why Is a Kitchen the Best Science Lab You Already Own?
Pick tonight’s dinner and list three science ideas hiding in it, like heat, mixing, microbes, or taste.