Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 232 · 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? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the iron setting (c) how dark the writing is (d) the same cotton bud
3. 3.⚖️ 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
4. 4.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a balloon (d) an adult with an iron
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a magnet (c) an adult with an iron (d) lemon juice
7. 7.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) writing the message (d) dipping the cotton bud
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a battery cell (d) white paper
9. 9.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) plugging in the iron (d) cutting the lemon
10. 10.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
11. 11.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
12. 12.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
13. 13.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) dipping the cotton bud
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
16. 16.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) letting the paper dry (d) plugging in the iron
17. 17.True or false: letting the paper dry is a job a child can do. (a) False (b) True
18. 18.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) ironing the paper
19. 19.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
20. 20.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) letting the paper dry
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) yeast (d) lemon juice
22. 22.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it is magnetic (d) it can burn skin
23. 23.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
25. 25.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
26. 26.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) a balloon
28. 28.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
29. 29.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
30. 30.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
31. 31.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) writing the message (d) plugging in the iron
32. 32.⚖️ 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) True (b) False
33. 33.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
34. 34.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) writing the message (d) dipping the cotton bud
35. 35.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
36. 36.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
37. 37.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
39. 39.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False

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