I am a S3 student this year. It is the first time for me to learn Chemistry, and there are many simple theories that I don't understand. Hope that you can help me.>3< (I am to stupid=V=)
1) What are the differnces between the hazardous warning labels of "flammable" and "oxidizing" ?
2) Would you describe the hazardous warning labels of "harmful" ? (I only know that the chemicals, which are harmful, cause us limited health risk when we swallowed them, breathed in or absorbed into skin. What is the limited health risk?) (COMPARE with TOXIC which is high health risk causing death)
3) Are volume, length and weight physical properties? Why?
(Although my teacher had said that they are extensive properties(because changing the state of water, the volume isn't same), I don't know the reason><)
4) What are the other examples of physical change accept changing the state of water(melting, boiling, condensation, freezing) and breathing?
5) Do sugar be broke down to form carbon dioxide and water? Is it a chemical change?
6) What are the differences between compound and mixture ? EXPLAIN + EXAMPLES
I am sorry to disturb all of you. THANK YOU=D
S3 simple chemical questions
2010-09-17 3:00 am
回答 (1)
2010-09-17 4:05 pm
✔ 最佳答案
1) Flammable: - This class includes solids, liquids, and gases capable of catching fire in the presence of a spark or open flame under normal working conditions.
Oxidizing:- These materials increase the risk of fire if they come in contact with flammable or combustible materials.
2)
Hazard symbols are recognizable symbols designed to warn about hazardous materials or locations. The hazardous warning symbols on household products were developed to indicate exactly why and to what degree a product is dangerous. It can be classified as Toxic, Caution, Warning, Biohazard, High Voltage ………….etc. Toxic symbols are placed on containers to confirm that the substance inside is dangerous in a way. Hong Kong may have different symbols from North America.
3)
Volume, length and weight are not physical properties. They are not characteristics of the substance because volume, length and weight depend on the amount of substance involved. Density, hardness and state at room temperature(solid, liquid and gas), melting point and boiling point are physical properties.
4)
Sublimation, evaporation and dissolving are other examples of physical change.
5)
Sugar breaks down into carbon dioxide and water. It is a chemical change.
6)
Mixture contains at least two pure substances. A compound is a pure substance that contains two or more elements in a fixed proportion. The atoms of elements are rearranged to form a new product. This new product is called compound. It has new physical and chemical properties, different from its elements. Element sodium and element chlorine are toxic, not for human consumption. They combine together to form a compound, sodium chloride, (table salt). Your food contains salt. Mixture is any two substances mixing together in any proportion. Example is adding sugar to a cup of coffee.
Run out of space………That is all. You are welcome to Email me if you still have problems. Cheer!
參考: WHMIS symbols
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