Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 895 · 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.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) cutting the lemon (d) dipping the cotton bud
3. 3.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) reading the message
4. 4.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
5. 5.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
6. 6.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
7. 7.True or false: cutting the lemon is a job for an adult. (a) False (b) True
8. 8.⚖️ 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
9. 9.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
10. 10.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same paper (c) the ironing time (d) how dark the writing is
12. 12.True or false: letting the paper dry is a job for an adult. (a) True (b) False
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
14. 14.🛟 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
15. 15.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
16. 16.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
18. 18.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
19. 19.🧺 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) turmeric powder (d) a small bowl
20. 20.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
21. 21.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
22. 22.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) yeast (c) a balloon (d) a mirror
25. 25.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
26. 26.🛟 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
27. 27.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) dipping the cotton bud
29. 29.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
30. 30.True or false: putting the iron away is a job for an adult. (a) False (b) True
31. 31.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) cutting the lemon (d) putting the iron away
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
33. 33.⚖️ 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) the kind of juice (c) the same paper (d) the iron setting
34. 34.⚖️ 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
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a small bowl (d) a magnet
36. 36.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
37. 37.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
38. 38.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
39. 39.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
40. 40.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) reading the message (d) writing the message

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