Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 737 · 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 iron setting is kept the same. (a) False (b) True
2. 2.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) letting the paper dry (d) writing the message
3. 3.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) putting the iron away
4. 4.⚖️ 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
5. 5.⚖️ 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 measure it (c) we keep it the same
6. 6.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) writing the message
7. 7.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
8. 8.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is cold (d) it is sticky
10. 10.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
11. 11.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) dipping the cotton bud (c) putting the iron away (d) plugging in the iron
12. 12.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) lemon juice (d) yeast
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
15. 15.True or false: letting the paper dry is a job for an adult. (a) False (b) True
16. 16.⚖️ 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
17. 17.True or false: plugging in the iron is a job for an adult. (a) True (b) False
18. 18.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
19. 19.⚖️ 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 kind of juice (c) how dark the writing is (d) the same cotton bud
20. 20.🧺 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) turmeric powder
21. 21.True or false: putting the iron away is a job for an adult. (a) False (b) True
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) a cotton bud (d) a small bowl
23. 23.🍋 Which of these steps is a job for an adult? (a) writing the message (b) ironing the paper (c) reading the message (d) dipping the cotton bud
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
25. 25.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) writing the message
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) a mirror
27. 27.True or false: cutting the lemon is a job for an adult. (a) False (b) True
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) it gets darker (d) the paper floats
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
30. 30.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
31. 31.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
32. 32.⚖️ 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 same cotton bud (c) the kind of juice
33. 33.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a battery cell (d) white paper
35. 35.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
36. 36.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
37. 37.⚖️ 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
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: turmeric powder is needed for the secret lemon message. (a) False (b) True
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a mirror (c) a small bowl (d) lemon juice

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