Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 485 · 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.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
4. 4.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) a mirror (d) a small bowl
5. 5.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
6. 6.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
7. 7.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
8. 8.True or false: cutting the lemon is a job for an adult. (a) True (b) False
9. 9.⚖️ 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
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a small bowl (d) a cotton bud
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) white paper (d) a mirror
14. 14.⚖️ 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) how dark the writing is (c) the same paper (d) the kind of juice
15. 15.True or false: white paper is needed for the secret lemon message. (a) False (b) True
16. 16.True or false: writing the message is a job a child can do. (a) True (b) False
17. 17.True or false: letting the paper dry is a job a child can do. (a) False (b) True
18. 18.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) lemon juice (d) an adult with an iron
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
22. 22.⚖️ 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 keep it the same (c) we change it
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) an adult with an iron (d) lemon juice
24. 24.⚖️ 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 measure it (c) we keep it the same
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
26. 26.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) ironing the paper
27. 27.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
28. 28.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) dipping the cotton bud
29. 29.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) a mirror
31. 31.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud
32. 32.True or false: ironing the paper is a job a child can do. (a) True (b) False
33. 33.⚖️ 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 measure it (c) we keep it the same
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) a balloon (d) lemon juice
35. 35.⚖️ 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) the ironing time (c) how dark the writing is
36. 36.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
37. 37.⚖️ 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
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
39. 39.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) white paper (d) a battery cell

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