Lab Safety

1. Report all accidents regardless of how minor to your teacher.
2. Work in the lab only when the teacher is present or when you have permission to do so.
3. Never indulge in horseplay or behavior that could lead to injury of others.
4. Before beginning work in lab, clean the lab bench top and your glassware.
5. Use goggles and lab aprons when instructed to do so.
6. Due to the dangers of broken glass and corrosive liquid spills in the lab, open sandals or bare feet are not permitted in the lab.
7. Learn the location and proper usage of the eyewash fountain, fire extinguisher, safety shower, fire alarm box, office intercom button, evacuation routes, clean-up brush and dust pan, glass/chemical disposal can.
8. For minor skin burns, immediately plunge the burned area into cold water and notify the teacher.
9. If you get any chemical in your eye, immediately wash the eye with the eye-wash fountain and notify the teacher.
10. Never look directly into a test tube. View the contents from the side.
11. Never smell a material in a test tube or flask directly. Instead, with your hand, "fan" some of the fumes to your nose carefully.
12. Immediately notify the teacher of any chemical spill and clean up the spill as directed.
13. Never take chemical stock bottles to the lab benches.
14. Use equipment only as directed:

a. never place chemicals directly on the pan balances. b. use glycerin when inserting glass tubing into rubber stoppers. c. be cautious of glassware that has been heated. d. add boiling chips to liquid that is to be heated before heating. e. point test tubes that are being heated away from you and others.

15. Never taste any material in the lab
16. Food, drink and gum are prohibited in lab.
17. Never add water to concentrated acid solutions. The heat generated may cause spattering. Instead, as you stir, add the acid slowly to water.
18. Read the label on chemical bottles at least twice before using the chemical. Many chemicals have names that are easily confused.
19. Return all lab materials and equipment to their proper places after use.
20. Upon completion of work, wash and dry all equipment, your lab bench and your clean-up area.

Heating and cooling of a pure substance

Lab 3B

Separation of a Mixture by Paper ChromatographyChromatography is one technique used by chemists to separate mixture of chemical compounds in order to identify or iso;ate their components on chromatography, mixture are separated according to the different solubilities of the components in liquids, or their adsorption on solids.
The method of identifying components is to calculate the Rf value of each.
Rf=d1/d2 where d1=distance traveled by solute
d2=distance traveled by solvent
the lab report:
Objective: 1. To assemble and operate a paper chromatography apparatus
2. To study the meaning and significance of Rf values
3. To test various food colourings and to calculate their Rf values
4. To compare measured Rf values with standard Rf values
5. To separate mixtures of food colourings into their components
6. To identify the components of mixture by means of their Rf values

Material and Equipment:Refer to page 33 in Health Lab Text, Lab 3B
Procedure:
Refer to page 33 in Health Lab Text, Lab 3B

Data and Observation:Attached to the back of the lab report.(on the paper....)

Analysis of Results:1. A, We tested the yellow colouring. It contains Yellow #6
B. We didn't get any.
2. Green food colouring contains about 1/3 of yellow colouring(Yellow #6) and 2/3 of blue colouring(Blue #2).
3. The unknown mixture is composed of 1/2 of red colouring(Red #4), 1/3 of blue colouring(Blue #2) and 1/6 of Yellow colouring(Yellow #6)
4. The ink mark might be blurred and move up.
5. The green colouring can be decomposed into blue and yellow, but red, yellow and blue colourings cannot be decomposed.

Following-Up Questions1. The Rf of those colourings are 0.78 and 0.38. They are likely to be Red#3 and Yellow #6.
2. d1= 12*1.0 = 12 d2 = 12*0.41 = 4.92 Δd = 12-4.92 = 7.08cm
3. There is no way that a solute move above the solvent. It is impossible.

ConclusionFrom this lab, we got to know the way we separate a mixture by Paper Chromatography. The Rf value means the ratio of distances raveled by solute and solvent. Different substances usually have different Rf values. We can use this property to separate different substances. And we can also identify the substances by checking the table of Rf values.

separation

Separation:-Basis for separation: Different components and properties-components in a mixture retain their identities
-the more similar the properties are, the more difficult it is to separate them.
-Strategy: use any possible way to discriminate between components with different properties.

Hand Separation & Evaporation:-Hand separation (Solid+Solid)
-Use a magnet or sieve
-Evaporation(Solid dissolved in liquids) boil away the liquid and the solids remain

Filtration (Solids NOT dissolve in water)-use porous filter to separate the solids out. (If the pores are smaller than the solids)
-use filter paper-residue left in filter paper, filtrate, filtrate goes through filter paper

Crystallization(Solid in liquid)-precipitation is the conversion of a solution to solid form by chemical or physical change
-solids are then separated by filtration or floatation
-saturated solution of a desire solid
-evaporate or cool-solids come out as pure crystals. Then crystals are filtered from remaining solvent.

Gravity Separation-solids based on density
-A centrifuge whirls the test tube around at high speed forcing the denser materials to the bottom. Work best for small volumes.

Solvent Extraction-a component moves into a solvent shaken with the mixture
-works best with solvents that dissolve only one components
-mechanical mixture:(Solid & Solid)
2 solids use liquid, one dissolved, get another one.
-solution: solvent is insoluble with solvent already present.
solvent dissolved 1 or more desire solids and leaves unwanted solids behind.
(If shaken in a separator funnel, the liquids will form layers then drain the solvent to leave the wanted material)

Distillation(Liquid in liquid solution)-heating a mixture can cause low-boiling components to volatilize（vaporize）
-distillation is collecting and condensing volatilized components
-liquids with lowest boiling temperature boil first---vapor ascents to distillation flask and enters condenser; gas cools and condenses back to liquid dropping the distillate as a purified liquid.

Chromatography-flow the mixture over a material that retains some components more than others, so different components flow over the material at different speeds.
-a mobile phase sweeps the sample over a stationary phase
-can separate very complex mixtures
-very small sample sizes analyses----highly accurate & precise
-separated components can be collected individually

Paper Chromatography(PC):-stationary phase is liquid soaked into a sheet or strip paper mobile phase is a liquid solvent some components spend more time in stationary phase than other components appear as separate spots spread out on the paper after drying or "developing".

Sheet Chromatography:Thin layer chromatography (TLC）:-stationary phase is a thin layer of absorbent (Al202 or So2 usually) coating a sheet of plastic or glass some components bond to the absorbent strongly other more weakly as with paper chromatography, components appear as spots on the sheet.

Naming ionic, covalant and Acidic

Acids are formed when a compound composed of Hydrogen ions and a negatively charged ion are dissolved in water(aqueous, aq)！-ions separate when dissolved in water
-H+ ions join with H2O from H3O+ (Hydronium ion)
ex: H + Cl --> HCl
HCl(g)+H2O-->H3O(aq)+Cl(aq)

How to name acids?
For Simple Acids:1. use "hydro" as the beginning
2. last syllable of the nonmetal is dropped and replaced with "-ic"
3. add "acid" at the end.

formula:*****ide ===> hydro*****ic acid
ex.HF: hydrofluoric acid
HCl: hydrochloric acid
HBr: hydrobromic acid
HCN: hydrocyanic acid

For Complex Acids:1. -ate replace with "-ic"
-ite replace with "-ous"
2. "Acid" at the end of the name

formula:*****ate ===> *****ic acid
*****ite ===> *****ous acid

ex.HNO3: Nitric acid
HNO2: Nitrous acid
H3PO4: Phosphoric acid
H2SO4: Sulphuric acid (exception)

Lab---Chemical & Phsical Change

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

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.

Matter & Chemical and Phsical Change

 MATTER?

----Anything that has mass and takes up space.

                                 

Matter

includes

1.Pure Substances                                             

---one set of properties

---one kind of particle

(1) Element

---simplest form(cannot be decomposed)

---made of atoms 1.metal  2.nonmetal 3.metalloid

(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

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

Unit conversion

 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