Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 39 · 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.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) an adult with an iron (d) a balloon
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) physical (d) magnetic
3. 3.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a small bowl (d) an adult with an iron
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) an adult with an iron (d) a small bowl
7. 7.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
10. 10.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
11. 11.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
12. 12.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
13. 13.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
14. 14.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) yeast (d) lemon juice
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
18. 18.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
19. 19.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
20. 20.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a small bowl (d) a mirror
21. 21.⚖️ 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
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the iron setting (d) the same paper
23. 23.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) cutting the lemon (d) putting the iron away
24. 24.True or false: cutting the lemon is a job a child can do. (a) True (b) False
25. 25.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
26. 26.True or false: plugging in the iron is a job for an adult. (a) True (b) False
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
28. 28.True or false: yeast is needed for the secret lemon message. (a) True (b) False
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
30. 30.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) cutting the lemon
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) white paper (d) lemon juice
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
33. 33.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) white paper (d) a cotton bud
36. 36.⚖️ 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
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) turmeric powder (d) a balloon
38. 38.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
39. 39.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
40. 40.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) lemon juice (d) yeast

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