Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 692 · 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.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice (d) the same paper
3. 3.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) writing the message
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
5. 5.⚖️ 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
8. 8.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a magnet (d) white paper
10. 10.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) green (d) blue
11. 11.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
12. 12.⚖️ 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
13. 13.⚖️ 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
14. 14.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) dipping the cotton bud (d) cutting the lemon
15. 15.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
17. 17.⚖️ 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 keep it the same (c) we change it
18. 18.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
19. 19.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) lemon juice (d) a balloon
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 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
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) lemon juice (d) a mirror
25. 25.True or false: cutting the lemon is a job a child can do. (a) True (b) False
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) yeast (d) a small bowl
28. 28.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
29. 29.True or false: putting the iron away is a job for an adult. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) cutting the lemon
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
32. 32.True or false: cutting the lemon is a job for an adult. (a) True (b) False
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
34. 34.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
35. 35.True or false: writing the message is a job a child can do. (a) True (b) False
36. 36.⚖️ 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
37. 37.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
38. 38.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
39. 39.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
40. 40.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) ironing the paper

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