the sentences below are wrong, please write out the places where there are mistakes. Also write out the correct version:
1) Physical change, like burning, are difficult to reverse.
2) A liquid is always formed during a precipitation reaction.
3) The substances you start with in a chemical reaction are called the products.
4) Energy is usually given out when elements are formed from a compound.
5) The new substances formed in chemical reactions are called reactants.
6) All chemical reactions need heat to start then off.
Please answer these questions in english, thank you =)
science questions
2010-11-17 8:29 am
回答 (2)
2010-11-17 8:49 am
✔ 最佳答案
1) Physical change, like burning, are difficult to reverse.Physical changes to Chemical
Since buring is a process react with oxygen, new product is formed and it is not a physical change.
2) A liquid is always formed during a precipitation reaction.
Liquid changes to Solid
Since precipitation reaction is a reaction which gives out insoluble solid, if no solid is formed, it is not a precipitation.
3) The substances you start with in a chemical reaction are called the products.
Products change to Reactants
Products are the substances after a reaction. Reactants are the substances you want them to react, which are before a reaction.
4) Energy is usually given out when elements are formed from a compound.
Usually changes to Never
If elements are formed from a compound, energy must be needed to break the bonding within the compound, so energy is consumed instead of being given out.
5) The new substances formed in chemical reactions are called reactants.
Reactants change to Product
Same reason as question 3.
6) All chemical reactions need heat to start then off.
All changes to Some
Not all chemical reactions need heat to start, for instance, reaction of group 1 elements with water.
2010-11-18 3:13 am
收錄日期: 2021-04-27 13:45:33
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