Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 297 · 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) reading the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) a small bowl (d) a cotton bud
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
4. 4.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
7. 7.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
8. 8.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) dipping the cotton bud (d) putting the iron away
9. 9.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
10. 10.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
11. 11.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) putting the iron away (c) dipping the cotton bud (d) writing the message
12. 12.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
13. 13.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) an adult with an iron (d) a mirror
14. 14.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
15. 15.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
17. 17.True or false: ironing the paper is a job for an adult. (a) True (b) False
18. 18.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
19. 19.🔮 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
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a mirror (c) a cotton bud (d) an adult with an iron
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the same paper (c) the kind of juice (d) the ironing time
22. 22.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) letting the paper dry
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
25. 25.True or false: writing the message is a job for an adult. (a) False (b) True
26. 26.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
27. 27.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
28. 28.🍋 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
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a cotton bud (d) lemon juice
30. 30.🛟 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
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a cotton bud (d) a battery cell
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) ironing the paper (d) dipping the cotton bud
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same paper
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a mirror
35. 35.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) dipping the cotton bud
36. 36.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) white paper (d) a balloon
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a balloon (c) turmeric powder (d) a battery cell
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) True (b) False
40. 40.⚖️ 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) the kind of juice (c) how dark the writing is

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