Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 321 · 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) putting the iron away (b) letting the paper dry (c) plugging in the iron (d) ironing the paper
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
3. 3.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) a balloon (d) a small bowl
5. 5.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
6. 6.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
7. 7.True or false: plugging in the iron is a job for an adult. (a) True (b) False
8. 8.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) ironing the paper (d) putting the iron away
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a mirror (d) a cotton bud
10. 10.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) reading the message
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a small bowl (d) an adult with an iron
12. 12.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) turmeric powder (d) an adult with an iron
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
16. 16.🛟 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
17. 17.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) turmeric powder (d) a balloon
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) a magnet (d) a small bowl
20. 20.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
21. 21.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
22. 22.True or false: writing the message is a job for an adult. (a) False (b) True
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
24. 24.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
25. 25.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
26. 26.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
27. 27.True or false: reading the message is a job for an adult. (a) True (b) False
28. 28.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
29. 29.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the kind of juice (d) the same paper
31. 31.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
32. 32.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
33. 33.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) an adult with an iron (d) white paper
35. 35.🍋 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
36. 36.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) physical (d) magnetic
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a mirror (d) a small bowl
38. 38.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) writing the message
39. 39.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
40. 40.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) yeast (d) a battery cell

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