Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 820 · 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.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a battery cell (d) white paper
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
3. 3.True or false: reading the message is a job a child can do. (a) False (b) True
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) lemon juice (d) a small bowl
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
6. 6.⚖️ 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 ironing time (c) the iron setting (d) how dark the writing is
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a mirror (c) an adult with an iron (d) a small bowl
8. 8.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
9. 9.True or false: reading the message is a job for an adult. (a) True (b) False
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) a battery cell (d) lemon juice
11. 11.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
13. 13.⚖️ 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 change it (c) we measure it
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
15. 15.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) reading the message (d) dipping the cotton bud
16. 16.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) letting the paper dry
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
18. 18.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
19. 19.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
20. 20.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) cutting the lemon (d) ironing the paper
21. 21.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
22. 22.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
23. 23.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
24. 24.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a balloon (d) white paper
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice
27. 27.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
28. 28.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
29. 29.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
30. 30.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) letting the paper dry (d) plugging in the iron
31. 31.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) lemon juice (d) a magnet
32. 32.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
33. 33.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
35. 35.True or false: putting the iron away is a job for an adult. (a) True (b) False
36. 36.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) letting the paper dry
37. 37.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
38. 38.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
40. 40.True or false: yeast is needed for the secret lemon message. (a) True (b) False

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