Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 542 · 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 is the odd one out? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
3. 3.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) dipping the cotton bud (d) reading the message
4. 4.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
5. 5.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
6. 6.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
7. 7.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) turmeric powder (d) a cotton bud
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) an adult with an iron (d) a mirror
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) the iron setting (d) the kind of juice
11. 11.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) letting the paper dry (d) reading the message
12. 12.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
13. 13.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a small bowl (d) a balloon
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
16. 16.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
17. 17.⚖️ 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
18. 18.⚖️ 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 measure it (c) we keep it the same
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) yeast (d) an adult with an iron
20. 20.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) writing the message (d) reading the message
21. 21.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) lemon juice (d) a small bowl
23. 23.True or false: reading the message is a job for an adult. (a) True (b) False
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) lick your fingers (d) skip washing
25. 25.True or false: ironing the paper is a job a child can do. (a) True (b) False
26. 26.🔮 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
27. 27.⚖️ 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 keep it the same (c) we measure it
28. 28.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) plugging in the iron (d) putting the iron away
30. 30.⚖️ 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
31. 31.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) an adult with an iron (d) white paper
33. 33.True or false: putting the iron away is a job a child can do. (a) False (b) True
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
35. 35.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
36. 36.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) whoever is fastest (d) any child
37. 37.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
38. 38.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
39. 39.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) writing the message (c) ironing the paper (d) plugging in the iron
40. 40.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True

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