Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 397 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) a small bowl (d) an adult with an iron
2. 2.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
3. 3.True or false: letting the paper dry is a job for an adult. (a) False (b) True
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
5. 5.⚖️ 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 same paper (c) how dark the writing is
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) a magnet (d) lemon juice
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) a small bowl (d) white paper
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a mirror (c) yeast (d) turmeric powder
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 kind of juice (b) the iron setting (c) the same cotton bud (d) the ironing time
11. 11.True or false: ironing the paper is a job a child can do. (a) True (b) False
12. 12.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
13. 13.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
16. 16.⚖️ 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
17. 17.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: white paper is needed for the secret lemon message. (a) False (b) True
19. 19.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
20. 20.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we change it (c) we measure it
22. 22.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
23. 23.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
24. 24.True or false: cutting the lemon is a job for an adult. (a) True (b) False
25. 25.🍋 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) dipping the cotton bud
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
27. 27.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
28. 28.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) letting the paper dry (d) ironing the paper
29. 29.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
30. 30.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) plugging in the iron (d) putting the iron away
31. 31.True or false: plugging in the iron is a job for an adult. (a) False (b) True
32. 32.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
33. 33.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
34. 34.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
35. 35.⚖️ 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
36. 36.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
38. 38.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
39. 39.⚖️ 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
40. 40.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) letting the paper dry

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