Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 735 · 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? True or false: the same paper is kept the same. (a) True (b) False
2. 2.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
4. 4.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
6. 6.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) writing the message (d) letting the paper dry
7. 7.True or false: writing the message is a job a child can do. (a) True (b) False
8. 8.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the kind of juice (d) the ironing time
10. 10.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
11. 11.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
12. 12.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
13. 13.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
14. 14.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
15. 15.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) dipping the cotton bud (d) writing the message
16. 16.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a small bowl (d) a magnet
19. 19.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
20. 20.⚖️ 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) True (b) False
21. 21.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is magnetic (d) it is sticky
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) the same cotton bud (c) how dark the writing is
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
24. 24.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a cotton bud (d) a battery cell
26. 26.⚖️ 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 keep it the same (c) we measure it
27. 27.🛟 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
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
29. 29.⚖️ 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
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a small bowl (d) a balloon
31. 31.True or false: yeast is needed for the secret lemon message. (a) False (b) True
32. 32.⚖️ 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
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
34. 34.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) dipping the cotton bud (d) writing the message
35. 35.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
36. 36.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
37. 37.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
38. 38.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
39. 39.True or false: white paper is needed for the secret lemon message. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it

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