Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 221 · 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 iron setting is what we measure. (a) True (b) False
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a battery cell (d) an adult with an iron
4. 4.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a cotton bud (d) a magnet
7. 7.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
8. 8.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) an adult with an iron (d) a small bowl
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
11. 11.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
12. 12.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) writing the message (d) ironing the paper
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
14. 14.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
15. 15.🍋 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) writing the message
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a magnet (d) turmeric powder
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
18. 18.⚖️ 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
19. 19.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
21. 21.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
22. 22.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
24. 24.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
25. 25.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
26. 26.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is (d) the ironing time
28. 28.True or false: plugging in the iron is a job for an adult. (a) False (b) True
29. 29.⚖️ 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
30. 30.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
31. 31.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
32. 32.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) a small bowl (d) a cotton bud
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) yeast (d) a small bowl
36. 36.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
37. 37.⚖️ 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 iron setting (c) the kind of juice (d) the same paper
38. 38.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True

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