Invisible Ink Experiment Worksheet

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

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