题干

小刚同学在实验室发现一瓶长期存放的氢氧化钙固体.对此他提出一个问题:这瓶氢氧化钙固体是否变质?

小刚认为氢氧化钙可能变质所依据的化学原理是(用化学方程式表示):____;

猜想:①该固体未变质;②该固体部分变质;③该固体完全变质.

设计实验:

操作步骤

现象

结论

____

有气泡产生

证明该固体已经发生变质

另取少量瓶中的白色粉未加入水中后,再取少许上层清液加入无色酚酞试液

____

证明该固体未完全变质

结论:通过现象分析,小刚确定猜想②成立.

上一题 下一题 0.0难度 选择题 更新时间:2019-06-25 03:07:09

答案(点此获取答案解析)

Ca(OH)2+CO2═CaCO3↓+H2O,取少量白色粉末于试管中,加稀盐酸,酚酞(溶液)变红

同类题5

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

____

At the beginning of 2005, Silly Buswas nothing more than a start up small business.Today, they have released(发行)four CDs all over the country, andmany music videos, which can be heard and seen on stations throughout theUnited States.____They have alsoworked with well known companies, such as Radio Disney, XM Radio and NBC.

You may be asking yourself,“So, how is their music making adifference?Whatmakes Silly Bus different from other kids'music?”_____Their first CD release focused onStandard of Learning (SOL) content for young children (Kindergarten through 2ndgrades).Thesongs on this album cover different topics, including math, grammar, science,physical fitness, and history.

For their second and third CDreleases, they teamed with preschool educators to write songs connected withlearning the alphabet.____Thesong TurkeyTime has fast become a national favorite, having been featured on NBC'sTodayShow the past two years on Thanksgiving Day.

____They devote to start many CDs andsingles.For example, Silly Bus wrote, performed and produced“Watch Me, I Can DoThis!”forimproved support of SportsBackers' Monument Avenue 10K.This encouraging songwas used to call on thousands of children to take part in the yearly kids runof the event.Silly Bus wrote, performed and produced“Artie,”the Kids Extra theme song.The song iswell received and often broadcasted in different TV stations and on the web.

A.Itis their focus on educational content.

B.Makingmore money with a creative idea.

C.Makinga Difference with Educational Music.

D.Theyhave played for many organizations and schools.

E.SillyBus is best popular among children and parents.

F.Thesesongs include both phonics and language techniques.

G.SillyBus has worked with several companies and non­profit organizations.