Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 429 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
2. 2.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
3. 3.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a balloon (d) a magnet
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) whoever is fastest (d) the youngest child
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
8. 8.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) turmeric powder (d) lemon juice
10. 10.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
11. 11.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a small bowl (d) a magnet
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
14. 14.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the ironing time (c) the kind of juice (d) the same paper
16. 16.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
20. 20.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the iron setting
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
23. 23.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
24. 24.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a balloon (d) white paper
26. 26.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a magnet (d) lemon juice
29. 29.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
30. 30.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) letting the paper dry
31. 31.True or false: cutting the lemon is a job for an adult. (a) True (b) False
32. 32.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
33. 33.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
34. 34.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) dipping the cotton bud (d) writing the message
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) white paper (d) a battery cell
36. 36.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) turmeric powder (d) white paper
37. 37.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
39. 39.True or false: plugging in the iron is a job a child can do. (a) False (b) True
40. 40.True or false: plugging in the iron is a job for an adult. (a) False (b) True

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