Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 494 · 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) not needed (b) needed
2. 2.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) lemon juice (c) a cotton bud (d) an adult with an iron
4. 4.⚖️ 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
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) how dark the writing is (c) the iron setting (d) the kind of juice
6. 6.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
7. 7.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
8. 8.🧺 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) yeast (d) a small bowl
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) blue words (d) dark brown words
10. 10.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) writing the message (d) letting the paper dry
11. 11.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same cotton bud (c) how dark the writing is (d) the iron setting
13. 13.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
15. 15.True or false: letting the paper dry is a job for an adult. (a) True (b) False
16. 16.True or false: plugging in the iron is a job a child can do. (a) True (b) False
17. 17.⚖️ 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
18. 18.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
19. 19.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
20. 20.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
21. 21.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
22. 22.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) writing the message (d) ironing the paper
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
24. 24.⚖️ 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
25. 25.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is sticky (d) it is cold
26. 26.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) letting the paper dry (d) writing the message
27. 27.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) white paper (c) a small bowl (d) an adult with an iron
29. 29.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
30. 30.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
31. 31.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) writing the message (d) dipping the cotton bud
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 keep it the same (b) we measure it (c) we change it
33. 33.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a small bowl (c) yeast (d) a magnet
35. 35.⚖️ 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 ironing time (c) how dark the writing is
36. 36.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) a magnet (d) lemon juice
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) an adult with an iron (d) a balloon
38. 38.🛟 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
39. 39.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) reading the message
40. 40.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed

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