Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 661 · 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 magnet for the secret lemon message? (a) not needed (b) needed
2. 2.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) reading the message (d) dipping the cotton bud
3. 3.⚖️ 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
4. 4.⚖️ 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) False (b) True
5. 5.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) how dark the writing is (c) the same paper (d) the same cotton bud
7. 7.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
8. 8.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is magnetic (d) it is cold
9. 9.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: cutting the lemon is a job for an adult. (a) False (b) True
11. 11.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a small bowl (d) a battery cell
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
14. 14.True or false: yeast is needed for the secret lemon message. (a) True (b) False
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a balloon (d) white paper
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) yeast (d) a small bowl
17. 17.⚖️ 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
18. 18.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) plugging in the iron (d) ironing the paper
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud
20. 20.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
21. 21.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
22. 22.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) dipping the cotton bud (d) reading the message
23. 23.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
24. 24.True or false: white paper is needed for the secret lemon message. (a) True (b) False
25. 25.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
26. 26.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
28. 28.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) letting the paper dry (d) plugging in the iron
29. 29.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
30. 30.⚖️ 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) True (b) False
31. 31.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
32. 32.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
33. 33.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
34. 34.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
35. 35.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
36. 36.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) ironing the paper (d) cutting the lemon
37. 37.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
38. 38.⚖️ 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
39. 39.True or false: letting the paper dry is a job for an adult. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False

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