2010年9月30日星期四

LAB:Physical change & Chemical change Sept.30

Lab Purpose:
   Learning how to infer the reactions are whether  chemical changes or physical changes. And record some recongnizable characteristics of chemical changes.

Materials and Equipments:
Refer to page 18 in Health Lab Text , Lab 2C
Equipments:
      4 small test tubes      10mmX75mm
      test tube rack
      4 medicine dropper
      glass square
      lab apron
      safety goggles
      four unknown chemical reagents(one is green, the others are all transparent)

procedure:
Refer to Page 18 in Health Lab Text, Lab 2C

Data and Observation:

Analysis of Results
B+A      Chemical Change
C+A      Physical Change
D+A      Chemical Change
C+B      Chemical Change
D+B      Chemical Change
D+C      Physical Change

Following-Up Questions:
a)Chemical change: Burn some papers, cook meat
b)Physical change: tear some papers, ice melt

Sources of Error:
There are some drops of liquid in the glass square.
That could be water or other solutions which might affect the results.

Conclusion:
According to the results of this lab, we conclude that chemical changes happen with new substances formed and physical changes take place with new substances formed.
Not like chemical changes, physical changes are reversable.
In this lab, chemical changes happen in the form of color changing, air bubbles and sediments generation.

2010年9月27日星期一

Matter Spet.27

What is MATTER?
----Anything that has mass and takes up space(Volume).
                                 
Matter includes
1.Pure Substances                                             
---one set of properties
---one kind of particle
(1) Element
---simplest form(cannot be decomposed)
---made of atoms ①metal  ②nonmetal ③metalloid
(2)compounds
----made of elements
---chemically combined
---smallest particle is a molecule(Ionic  &  Covalent)


2.Mixtures
---more than one set of properties and substances
---physically combined
(1)Homogeneous
---uniform throughout
---appears to have only one component
Ex: Solutions &  colloid
(2)Heterogeneous
---not uniform
---appears to have more than one component
Ex:   Salad Dressing (Suspensior & Mechanical Mixture)
       Water+oil


Physical Change vs. Chemical Change
Physical Change
---no new substance is formed
---chemical composition doesn't change
---reversible


Chemical Change
---new substances are formed
---irreversible
Ex: Burning & Cooking

reference video:
http://teachertube.com/viewVideo.php?title=Physical_Change_vs_Chemical_Change&video_id=40108

A few more properties for matter
---it is neither created nor destroyed(only changed form from one form to another)

Three States
(1)Solid
---rigid, don't change shape easily and experiences small changes in volume
(2)Liquid
---takes the shape of the container and experiences slight changes in volume when heated
(3)Gases
---takes the shape of the container and experiences drastic change in volume when heated

2010年9月23日星期四

First Lesson: Unit Conversion!

All measurement in science come in two parts: the number and the unit, having one without the other makes no sense!


SI Metric:
1. SI stands for systeme internationale
2. It is a French system dating back to the early 1800s
3. It uses powers of 10!

The Canceling Method for unit conversions: ^_^
Derived quantities include units created by combining base quantities through multiplication or division
ex. m^2(m*m)——Area
     cm^3 (cm*cm*cm)——Volume
     km/h  or  m/s——speed
     g/L  ——density


Convert:
ex: 8km/ms——>cm/s
8km       10^3 m    10^2 m     10^3 ms
—— × ———— × ———— ×———— = 8×10^8 cm/s
 ms          1km            1m              1s