Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 450 · 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? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
4. 4.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) a cotton bud (d) an adult with an iron
7. 7.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) cutting the lemon
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
9. 9.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
10. 10.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
11. 11.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) plugging in the iron (d) cutting the lemon
15. 15.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
16. 16.True or false: reading the message is a job a child can do. (a) True (b) False
17. 17.True or false: putting the iron away is a job a child can do. (a) True (b) False
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) lemon juice (d) a cotton bud
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
20. 20.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
21. 21.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) letting the paper dry
22. 22.⚖️ 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 same paper
23. 23.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a mirror (d) white paper
24. 24.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) putting the iron away
25. 25.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) reading the message (d) writing the message
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) a magnet (d) a small bowl
27. 27.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) lemon juice (c) yeast (d) a balloon
29. 29.True or false: reading the message is a job for an adult. (a) True (b) False
30. 30.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
32. 32.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) a cotton bud (d) an adult with an iron
34. 34.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
35. 35.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) cutting the lemon
36. 36.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
37. 37.True or false: putting the iron away is a job for an adult. (a) False (b) True
38. 38.True or false: plugging in the iron is a job for an adult. (a) True (b) False
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) turmeric powder (d) an adult with an iron
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same

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