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12 tháng 11 2021

báo cáo

18 tháng 1 2022

sai môn!~

21 tháng 1 2022

a. PTC: Sắt + Oxi \(\rightarrow^{t^o}\) Oxit sắt từ

b. Dấu hiệu: Sắt để lâu trong không khí bị gỉ

Bởi vì trong không khí có Oxi nên sắt bị Oxi hoá thành Oxit sắt từ làm sắt bị gỉ

c. Phản ứng trên có hại cho con người, vì sắt bị gỉ làm hỏng đồ vật, dụng cụ của con người trong sinh hoạt

d. Các biện pháp:

- Mã kẽm

- Sơn

- Sử dụng các loại hợp kim sắt không gỉ

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12 tháng 11 2021

TL

ko thấy bài do quá mờ

HT

. Fill in each blank with the correct word: more, fewer or less.1. Susan has ____________ homework than Mary, so Mary has to work harder than Susan.2. The new law limits smoking in public. There are _________ places where people can smoke.3. This factory has ____________ workers than that one, so it needs more.4. There are ____________ cars in the street at this time. The traffic is so heavy.5. Class 7A has 40 students, and Class 7C has only 36 students. Class 7A has ____________ students than...
Đọc tiếp

. Fill in each blank with the correct word: more, fewer or less.


1. Susan has ____________ homework than Mary, so Mary has to work harder than Susan.


2. The new law limits smoking in public. There are _________ places where people can smoke.


3. This factory has ____________ workers than that one, so it needs more.


4. There are ____________ cars in the street at this time. The traffic is so heavy.


5. Class 7A has 40 students, and Class 7C has only 36 students. Class 7A has ____________ students than Class 7B.


6. ____________ fruits are now in season in the south. There are plenty of fruits now.


7. Farmers have ____________ time off than workers. Farmers work harder than workers.


8. The weather in winter is worse than that in summer. People get ____________ colds in summer than in winter.


9. I think we don’t have many public holidays. We ought to have ____________.


10. We are lucky. We work ____________ hours than any workers

 

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1. Alternative sources of energy are ___________ and safe. A. enough B. not enough C. short D. abundant 2. Nuclear energy can provide enough electricity for the world’s needs, but it is very _____. A. risk B. risky C. endanger D. endangered 3. We should try to reduce energy ___________ as much as possible. A. production B. producers C. consumption D. consumers 4. We are looking for cheap, clean, ___________ sources of energy. A. polluting B. harmful C. expensive D. effective 5. Solar energy...
Đọc tiếp

1. Alternative sources of energy are ___________ and safe.

 

A. enough B. not enough C. short D. abundant

 

2. Nuclear energy can provide enough electricity for the world’s needs, but it is very _____.

 

A. risk B. risky C. endanger D. endangered

 

3. We should try to reduce energy ___________ as much as possible.

 

A. production B. producers C. consumption D. consumers

 

4. We are looking for cheap, clean, ___________ sources of energy.

 

A. polluting B. harmful C. expensive D. effective

 

5. Solar energy is ___________ and it can be replaced easily.

 

A. new B. renew C. renewable D. non-renewable

 

6. For many people living in rural areas, biogas is a cheap energy _______available.

 

A. method B. production C. supply D. consumption

 

7. People living in the slums never get good healthcare, ___________?

 

A. do they B. don’t they C. are they D. aren’t they

 

8. Everyone is ready for the game, ___________?

 

A. is it B. isn’t he? C. aren’t they D. is there

 

9. People move to big cities for a better ___________.

 

A. standard of living B. standard life C. standard living D. life of standard

 

10. Slidewalks are ___________ to moving walkways in airport.

 

A. familiar B. similar C. different D. same

 

11. Rio de Janeiro is very cultural ___________ city.

 

A. diverse B. diversity C. different D. same

 

12. Which is the best ___________ of transport for the future?

 

A. mean B. means C. traffic D. ways

 

13. Overcrowded places have a lot of problems, ___________?

 

A. don’t they B. does it C. doesn’t it D. have they

 

14. The schoolyard is very small, so there isn’t enough ________for students to play in.

 

A. rooms B. land C. space D. ground

 

15. I think in the future cities will be more crowded and the traffic will get___________.

 

A. good B. well C. worse D. worst

 

16. When ___________ people live in a small place, life can be very difficult.

 

A. a few B. few C. too much D. too many

 

17. Do you think it will be a (n) ___________ , green way to travel?

 

A. convenient B. polluted C. polluting D. inconvenience

 

18. Children in the slums have more diseases than _________ in wealthy areas.

 

A. them B. that C. those D. ø

 

19. Diseases ___________ more quickly in overcrowded areas.

 

A. move B. travel C. spread D. come

 

20. In Manila, over 30% of the population lives in ___________.

 

A. crops B. poverty C. shortage D. schooling

 

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12 tháng 11 2021

1. A. enjoyable B. comfortable C. convenient D. difficult

2. A. waste B. recycle C. conserve D. save

3. A. affect B. replace C. effect D. fly

4. A. density B. overcrowded C. crime D. megacity

5. A. drive B. cycle C. ride D. fly

6. A. wind B. gasoline C. coal D. natural gas

7. A. float B. slum C. hunger D. explosion

8. A. safely B. poverty C. slumdog D. space

9. A. abundant B. short C. plentiful D. unlimited

10. A. driver B. doctor C. criminal D. student

12 tháng 11 2021

noi boi nit ns jwmj

12 tháng 11 2021

Trong các dãy chất sau, dãy nào toàn là hợp chất? *   Rượu uống, khí nitrogen, sữa tươi, nước khoáng.   Khí oxygen, khí hydrogen, nước cất, muối ăn tinh khiết   Nước sông, muối ăn, đường, không khí.   Khí Carbon dioxide, đường tinh khiết, nước cất, muối ăn tinh khiết

HT

12 tháng 11 2021

TL :

Today is Friday

HT

12 tháng 11 2021

TL:

Today is friday

HT

12 tháng 11 2021
a) PTHH: CaCO3 ——t°——> CaO + CO2 b) Theo định luật bảo toàn khối lượng ta có : m CaCO3 = m CaO + m CO2 m CO2 = 200 – 112 m CO2 = 88