物質が固体、液体、気体に変わる温度を沸点と融点って言うんだ。これを理解すると、なぜ氷が溶けたり水が沸騰したりするのかがよくわかるよ。テストでもよく出るから、しっかりマスターしよう！
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Updated May 4, 2026
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物質の沸点と融点に関する基本知識
1 / 5
沸点と融点の基本
君の身の回りにある物質は、温度によって固体、液体、気体に変わるよね。この変化を状態変化と呼ぶんだ。
融点は固体が液体に変わる温度のこと。氷が水になる0℃が水の融点だ。沸点は液体が気体に変わる温度で、水が水蒸気になる100℃が水の沸点になる。
凝固点は液体が固体になる温度だけど、実は融点と全く同じ温度なんだ。水なら0℃で、温めるときは「融点」、冷やすときは「凝固点」と呼び方を変えるだけ。
ココがポイント！ 物質によって融点と沸点は決まっていて、これがその物質の「個性」みたいなものになるよ。
状態変化と温度の詳しい仕組み
氷を熱していくとどうなるか見てみよう。最初は氷の温度がどんどん上がっていくよね。
でも0℃に達すると、とても大事なことが起こる！氷が全部溶けて水になるまで、温度は0℃のまま変わらないんだ。熱を加えているのに温度が上がらないなんて不思議だよね。
これは加えた熱が温度を上げるためじゃなくて、状態を変化させるために使われているから。水でも同じで、100℃で沸騰が始まると、全部水蒸気になるまで温度は100℃のまま止まる。
テストに出やすい！ この「温度が変わらない時間」がグラフでは平らな線として表示されるよ。
グラフの読み取り方法
温度と時間のグラフはテストでよく出題される。グラフの平らな部分を見つけるのがコツだ。
最初の平らな部分が融点（固体と液体が混ざった状態）、次の平らな部分が沸点（液体と気体が混ざった状態）を表している。
物質によって融点と沸点は全然違うよ。エタノールの沸点は78℃だから、お湯よりも低い温度で沸騰する。鉄の融点は1538℃だから、普通の火では溶けないんだ。
覚えておこう！ 純粋な物質ははっきりした融点・沸点があるけど、食塩水のような混合物にははっきりした沸点がないよ。
例題で理解を深めよう
グラフ問題を解くときは、平らな部分を探すのが最初のステップ。最初に温度が一定になる部分が融点、次に一定になる部分が沸点だ。
グラフのAの部分（融点に達する前）では物質は固体、Bの部分（融点と沸点の間）では液体の状態になっている。
状態変化している間は、いくら熱を加えても温度は変わらない。この理由は、熱エネルギーが状態変化そのものに使われるからなんだ。
実生活でも役立つ！ 山の頂上では気圧が低いから、水は100℃より低い温度で沸騰するよ。圧力によって沸点は変わるんだ。
テスト対策の重要ポイント
純粋な物質は融点と沸点がはっきり決まっているけど、混合物（食塩水など）は沸騰している間も温度が上がり続ける。これはテストでよく狙われるポイントだ。
融点と凝固点は同じ温度だということも忘れずに。水なら0℃で、熱しているときは「融点」、冷やしているときは「凝固点」と呼ぶだけ。
グラフの平らな部分が融点や沸点を示していることをしっかり覚えて、たくさん練習問題を解いてみよう。慣れれば簡単に見分けられるようになるよ。
最終チェック！ 状態変化の最中は温度が一定、物質によって融点・沸点は決まっている、混合物にははっきりした融点・沸点がない、この3つが超重要だ。
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
物質の沸点と融点に関する基本知識
物質が固体、液体、気体に変わる温度を沸点と融点って言うんだ。これを理解すると、なぜ氷が溶けたり水が沸騰したりするのかがよくわかるよ。テストでもよく出るから、しっかりマスターしよう！
沸点と融点の基本
君の身の回りにある物質は、温度によって固体、液体、気体に変わるよね。この変化を状態変化と呼ぶんだ。
融点は固体が液体に変わる温度のこと。氷が水になる0℃が水の融点だ。沸点は液体が気体に変わる温度で、水が水蒸気になる100℃が水の沸点になる。
凝固点は液体が固体になる温度だけど、実は融点と全く同じ温度なんだ。水なら0℃で、温めるときは「融点」、冷やすときは「凝固点」と呼び方を変えるだけ。
ココがポイント！ 物質によって融点と沸点は決まっていて、これがその物質の「個性」みたいなものになるよ。
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状態変化と温度の詳しい仕組み
氷を熱していくとどうなるか見てみよう。最初は氷の温度がどんどん上がっていくよね。
でも0℃に達すると、とても大事なことが起こる！氷が全部溶けて水になるまで、温度は0℃のまま変わらないんだ。熱を加えているのに温度が上がらないなんて不思議だよね。
これは加えた熱が温度を上げるためじゃなくて、状態を変化させるために使われているから。水でも同じで、100℃で沸騰が始まると、全部水蒸気になるまで温度は100℃のまま止まる。
テストに出やすい！ この「温度が変わらない時間」がグラフでは平らな線として表示されるよ。
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グラフの読み取り方法
温度と時間のグラフはテストでよく出題される。グラフの平らな部分を見つけるのがコツだ。
最初の平らな部分が融点（固体と液体が混ざった状態）、次の平らな部分が沸点（液体と気体が混ざった状態）を表している。
物質によって融点と沸点は全然違うよ。エタノールの沸点は78℃だから、お湯よりも低い温度で沸騰する。鉄の融点は1538℃だから、普通の火では溶けないんだ。
覚えておこう！ 純粋な物質ははっきりした融点・沸点があるけど、食塩水のような混合物にははっきりした沸点がないよ。
Sign up to see the contentIt's free!
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例題で理解を深めよう
グラフ問題を解くときは、平らな部分を探すのが最初のステップ。最初に温度が一定になる部分が融点、次に一定になる部分が沸点だ。
グラフのAの部分（融点に達する前）では物質は固体、Bの部分（融点と沸点の間）では液体の状態になっている。
状態変化している間は、いくら熱を加えても温度は変わらない。この理由は、熱エネルギーが状態変化そのものに使われるからなんだ。
実生活でも役立つ！ 山の頂上では気圧が低いから、水は100℃より低い温度で沸騰するよ。圧力によって沸点は変わるんだ。
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
テスト対策の重要ポイント
純粋な物質は融点と沸点がはっきり決まっているけど、混合物（食塩水など）は沸騰している間も温度が上がり続ける。これはテストでよく狙われるポイントだ。
融点と凝固点は同じ温度だということも忘れずに。水なら0℃で、熱しているときは「融点」、冷やしているときは「凝固点」と呼ぶだけ。
グラフの平らな部分が融点や沸点を示していることをしっかり覚えて、たくさん練習問題を解いてみよう。慣れれば簡単に見分けられるようになるよ。
最終チェック！ 状態変化の最中は温度が一定、物質によって融点・沸点は決まっている、混合物にははっきりした融点・沸点がない、この3つが超重要だ。
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user