Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 275 · 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 of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) letting the paper dry (d) writing the message
2. 2.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) the ironing time (d) how dark the writing is
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
5. 5.⚖️ 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
6. 6.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
7. 7.True or false: reading the message is a job a child can do. (a) True (b) False
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
10. 10.⚖️ 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) True (b) False
11. 11.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) turmeric powder (d) a mirror
12. 12.True or false: writing the message is a job for an adult. (a) False (b) True
13. 13.🛟 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
14. 14.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
15. 15.🛟 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
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a cotton bud (d) a mirror
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a balloon (d) an adult with an iron
18. 18.⚖️ 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 measure it (c) we change it
19. 19.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
20. 20.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
21. 21.⚖️ 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) True (b) False
22. 22.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
23. 23.⚖️ 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
24. 24.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) an adult with an iron (d) a cotton bud
26. 26.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
27. 27.True or false: plugging in the iron is a job for an adult. (a) False (b) True
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a battery cell (d) a small bowl
29. 29.⚖️ 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
30. 30.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) dipping the cotton bud
31. 31.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
32. 32.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) writing the message (d) cutting the lemon
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) lemon juice (c) a cotton bud (d) white paper
34. 34.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
35. 35.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
36. 36.⚖️ 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
37. 37.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
38. 38.⚖️ 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
39. 39.True or false: letting the paper dry is a job for an adult. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False

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