Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 343 · 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 lemon juice for the secret lemon message? (a) needed (b) not needed
2. 2.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
3. 3.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) an adult with an iron (d) white paper
5. 5.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) writing the message
6. 6.⚖️ 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 ironing time
7. 7.True or false: plugging in the iron is a job for an adult. (a) True (b) False
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
9. 9.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
10. 10.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) yeast (d) a cotton bud
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
13. 13.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
14. 14.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing
15. 15.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) a balloon (d) an adult with an iron
17. 17.⚖️ 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) True (b) False
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
19. 19.⚖️ 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
20. 20.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) dipping the cotton bud
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
22. 22.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
23. 23.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
24. 24.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
25. 25.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) magnetic (d) musical
26. 26.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
27. 27.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a battery cell (d) lemon juice
28. 28.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) writing the message (d) letting the paper dry
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) lemon juice (d) a magnet
30. 30.⚖️ 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
31. 31.⚖️ 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 keep it the same (c) we measure it
32. 32.⚖️ 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
33. 33.True or false: letting the paper dry is a job a child can do. (a) False (b) True
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) lemon juice (c) a small bowl (d) an adult with an iron
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) a cotton bud (d) a mirror
36. 36.🔮 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
37. 37.⚖️ 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
38. 38.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) a battery cell (d) an adult with an iron
39. 39.🔍 Which is the odd one out? (a) cutting the lemon (b) reading the message (c) putting the iron away (d) plugging in the iron
40. 40.⚖️ 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

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