Ôn tập môn Vật lí Lớp 6 - Chủ đề: Sự nở vì nhiệt của các chất - Năm học 2020-2021

Tuần: 01/02/2021 đến 06/02/2021 
Chủ đề: SỰ NỞ VÌ NHIỆT CỦA CÁC CHẤT 
PHẦN A: LÝ THUYẾT 
I. Chủ đề 17: SỰ NỞ VÌ NHIỆT CỦA CHẤT RẮN 
Câu 1: Nếu các kết luận về sự nở vì nhiệt của của chất rắn? 
- Nở ra khi nóng lên, co lại khi lạnh đi. 
- Các chất rắn khác nhau co dãn vì nhiệt khác nhau. 
- Khi sự co dãn vì nhiệt bị ngăn cản có thể gây ra lực rất lớn. 
Câu 2: Cấu tạo, hoạt động và ứng dụng của băng kép? 
- Cấu tạo: Băng kép gồm 2 thanh kim loại có bản chất khác nhau được tán chặt vào nhau dọc 
theo chiều dài của thanh. 
- Hoạt động: Dựa trên sự co dãn vì nhiệt khác nhau của các chất rắn khác nhau. Khi đốt nóng 
hay làm lạnh, băng kép đều cong lại. 
- Ứng dụng: Đóng, ngắt tự động mạch điện theo nhiệt độ (trong bàn là, trong "con chuột" của 
đèn huỳnh quang). 
* Chú ý: 
1/ Nhôm nở vì nhiệt nhiều hơn Đồng, Đồng nở vì nhiệt nhiều hơn Sắt. 
2/ Khi các chất dãn nở vì nhiệt: 
+ Thể tích (V) của vật tăng lên. 
+ Khối lượng (m) của vật không đổi. 
+ Khối lượng riêng (D) của vật gỉam đi → vật nhẹ đi 
𝐷 = 
𝑚
𝑉
3/ Chất nào nở ra vì nhiệt nhiều hơn thì co lại vì nhiệt nhiều hơn. 
II. Chủ đề 18: SỰ NỞ VÌ NHIỆT CỦA CHẤT LỎNG 
Câu 1: Nêu các kết luận sự nở vì nhiệt của chất lỏng? 
- Nở ra khi nóng lên, co lại khi lạnh đi. 
- Các chất lỏng khác nhau co dãn vì nhiệt khác nhau. 
- Khi sự co dãn vì nhiệt bị ngăn cản có thể gây ra lực khá lớn. 
Câu 2: So sánh sự nở vì nhiệt của chất rắn và chất lỏng? 
 Giống nhau: 
- Các chất rắn, lỏng đều nở ra khi nóng lên và co lại khi lạnh đi. 
- Khi sự co dãn vì nhiệt bị ngăn cản có thể gây ra lực lớn. 
- Các chất rắn, lỏng khác nhau nở vì nhiệt khác nhau. 
 Khác nhau: Chất lỏng nở vì nhiệt nhiều hơn chất rắn. 
* Chú ý: 
- Đặc biệt, đối với nước khi nhiệt độ tăng từ 00C → 40C thì nước co lại. 
- Ở 40C: V nhỏ nhất, D lớn nhất, nước nặng nhất. 
III. Chủ đề 19: SỰ NỞ VÌ NHIỆT CỦA CHẤT KHÍ 
Câu 1: Nêu các kết luận về sự nở vì nhiệt của chất khí? 
- Nở ra khi nóng lên, co lại khi lạnh đi. 
- Các chất khí khác nhau co dãn vì nhiệt giống nhau. 
- Khi sự co dãn vì nhiệt bị ngăn cản có thể gây ra lực khá lớn. 
Câu 2: So sánh sự nở vì nhiệt của chất Khí, chất Lỏng và chất Rắn? 
 Giống nhau: 
- Các chất rắn, lỏng, khí đều nở ra khi nóng lên và co lại khi lạnh đi. 
- Khi sự co dãn vì nhiệt bị ngăn cản có thể gây ra lực lớn. 
 Khác nhau: 
- Các chất rắn (lỏng) khác nhau nở vì nhiệt khác nhau. Các chất khí khác nhau nở vì nhiệt 
giống nhau. 
- Chất khí nở vì nhiệt nhiều hơn chất lỏng và chất rắn. 
PHẦN B: BÀI TẬP 
I. Chủ đề 17: SỰ NỞ VÌ NHIỆT CỦA CHẤT RẮN 
Bài 1: Hãy giải thích các hiện tượng sau: 
a/ Tại sao tôn lợp nhà có hình dạng gợn sóng? 
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b/ Tại sao giữa các thanh ray của đường xe lửa có các khe hở hẹp? 
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c/ Tại sao khi khám răng, bác sỹ thường căn dặn chúng ta không nên ăn thức ăn quá nóng hay 
quá lạnh? 
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d/ Tại sao vào mùa hè dây điện thường võng xuống nhiều hơn mùa đông? 
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e/ Em hãy giải thích vì sao khi rót nước sôi vào các li thủy tinh, các li này dễ bị nứt, vỡ? 
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f/ Khi rót nước nóng vào các li thủy tinh, li dày hay mỏng dễ bị vỡ hơn? Theo em, có những biện 
pháp nào để giảm thiểu sự vỡ li thủy tinh khi ta rót nước nóng vào chúng? 
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Bài 2: Hai quả cầu, một bằng Đồng và một bằng Sắt có kích thước bằng nhau. 
a/ Khi nung nóng lên cùng nhiệt độ thì quả cầu nào sẽ lớn hơn? Vì sao? 
b/ Khi làm lạnh xuống cùng một nhiệt độ thì quả cầu nào sẽ lớn hơn? Vì sao? 
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Bài 3: Một băng kép gồm một thanh Nhôm và Đồng. Nếu: 
a/ Đun nóng băng kép cong về phía thanh nào? Vì sao? 
b/ Làm lạnh băng kép cong về phía thanh nào? Vì sao? 
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Bài 4 : Chai thủy tinh có nút đậy bằng thủy tinh, khi để lâu ngày làm cho nút chai bị kẹt nên khó 
mở ra. Làm cách nào để mở được nút đó? Giải thích cách làm đó? 
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Bài 5: Hai ly thủy tinh chồng khít vào nhau. Một học sinh định dùng nước nóng và nước lạnh để 
tách 2 cái ly ra. Hỏi bạn đó phải làm thế nào? Giải thích cách làm đó? 
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Bài 6: Quả cầu bằng Nhôm bị kẹt trong một vòng bằng Sắt. Để tách quả cầu ra khỏi vòng thì 
một học sinh đem hơ nóng cả quả cầu và vòng. Hỏi bạn đó có tách được quả cầu ra khỏi vòng 
hay không? Vì sao? 
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Bài 7: Một băng kép gồm một thanh Nhôm và Sắt. Khi làm lạnh băng kép cong về phía thanh 
Nhôm. Khi đun nóng băng kép cong về phía thanh nào? Vì sao? 
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Bài 8: Một băng kép gồm một thanh Đồng và một thanh Nhôm, đặt ngang trên giá đỡ. Khi làm 
lạnh,băng kép cong lên trên. Hỏi thanh Nhôm nằm trên hay dưới? 
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Bài 9: Ở 00C thanh ray bằng Sắt có chiều dài 15m. Nếu nhiệt độ tăng thêm 300C thì chiều dài 
thanh ray là bao nhiêu? Biết rằng khi tăng thêm 10C của chiều dài của Sắt tăng thêm 
0,0000012m so với chiều dài ban đầu.. 
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Chủ đề 18: SỰ NỞ VÌ NHIỆT CỦA CHẤT LỎNG 
Bài 1: Hãy giải thích các hiện tượng sau: 
a/ Khi đun nước ta có nên đổ nước đầy ấm hay không? Vì sao? 
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b/ Tại sao khi đóng chất lỏng vào chai, ta không bao giờ đóng đầy chai? 
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c/ Tại sao khi bỏ nước đá lạnh vào nước thì nước đá lạnh nổi lên trên? 
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d/ Khi đun nóng, khối lượng riêng của chất lỏng tăng hay giảm? Giải thích? 
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Bài 2: Các vật cùng thể tích ban đầu. Và tăng, giảm nhiệt độ giống nhau: 
a/ Sắp xếp theo thứ tự sự nở vì nhiệt từ nhiều đến ít: Rượu, Nước, Sắt, Nhôm. 
b/ Sắp xếp theo thứ tự sự co vì nhiệt từ ít đến nhiều: Đồng, Thép, Thủy ngân, Nước. 
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Bài 3: Các vật Đồng, Rượu, Nước, Sắt có thể tích ban đầu là 50cm3. Sau đó chúng tăng nhiệt độ 
thêm 600C. Hãy: 
a/ Sắp xếp sự tăng thể tích của theo thứ tự từ ít đến nhiều. 
b/ Sắp xếp sự tăng khối lượng riêng của theo thứ tự từ nhiều đến ít. 
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Bài 4: Một bình đựng Rượu và một bình đựng nước có cùng thể tích 1 lít ở 00C. Khi nung nóng 
hai bình lên nhiệt độ t= 500C thì thể tích của Rượu là 1,058 lít và thể tích của Nước là 1,012 lít. 
a/ Tính độ tăng thể tích của Rượu và thể tích của Nước? 
b/ Chất nào dãn nở vì nhiệt nhiều hơn? 
c/ Tại sao khi đun nóng chất lỏng khối lượng riêng (D) lại giảm xuống? 
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Chủ đề 19: SỰ NỞ VÌ NHIỆT CỦA CHẤT KHÍ 
Bài 1: Hãy giải thích các hiện tượng sau: 
a/ Khi quả bóng bàn bị móp làm thế nào để nó căng phồng trở lại? Giải thích cách làm đó? 
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b/ Vào mùa hè ta có nên bơm lốp xe quá căng không? Tại sao? 
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c/ Tại sao khi đổ nước sôi vào bình thủy (chưa đầy) mà đóng nắp lại ngay thì nắp bị bật ra? 
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d/ Tại sao không khí nóng lại nhẹ hơn không khí lạnh? 
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Bài 2: 
a/ Tại sao máy lạnh thường được gắn ở trên cao, còn lò sưởi lại đặt ở dưới thấp? 
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b/ Chai nhựa rỗng được đậy kín nắp (bên trong chứa đầy không khí) bỏ vào tủ lạnh thì bị bẹp 
vào. Giải thích vì sao? 
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Bài 3: Các chất Sắt, Nước, không khí có thể tích ban đầu là 1dm3. Sau khi đun nóng lên nhiệt 
độ t = 500C thì: 
a/ Thể tích của ba chất này thay đổi như thế nào? 
b/ Sắp xếp sự nở vì nhiệt từ ít đến nhiều? 
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Bài 4: Sắp xếp sự nở vì nhiệt theo thứ tự: 
a/ Tăng dần: Sắt, Nhôm, Nước, Rượu, khí Ôxi. 
b/ Giảm dần: Đồng, Nước, Thủy ngân, Không khí, Nhôm. 
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Bài 5: Các chất sau có cùng thể tích và nhiệt độ ban đầu. Sắp xếp thể tích của vật từ nhỏ đến lớn 
khi làm lạnh chúng: 
a/ Đồng, Nước, Sắt, khí Ôxi. 
b/ Nhôm, Đồng, Thủy ngân, Không khí, Nước. 
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