Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 285 · 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 the one thing we change? (a) how dark the writing is (b) the same cotton bud (c) the kind of juice (d) the ironing time
2. 2.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) lemon juice (d) a small bowl
4. 4.⚖️ 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 keep it the same (c) we measure it
5. 5.🔮 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
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) a small bowl (d) white paper
7. 7.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
8. 8.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
9. 9.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
13. 13.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) white paper (d) lemon juice
15. 15.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
16. 16.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
17. 17.🧺 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 battery cell (d) white paper
18. 18.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
19. 19.🍋 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
20. 20.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
22. 22.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) letting the paper dry (d) putting the iron away
23. 23.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) putting the iron away (d) cutting the lemon
24. 24.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a cotton bud (d) yeast
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
27. 27.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) no, it stays brown (d) yes, if shaken
28. 28.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
30. 30.⚖️ 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 measure it (c) we change it
31. 31.⚖️ 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
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
34. 34.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
35. 35.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) turmeric powder (d) an adult with an iron
37. 37.⚖️ 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
38. 38.True or false: plugging in the iron is a job a child can do. (a) True (b) False
39. 39.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
40. 40.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud

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