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Chemistry

Chemistry

Chemical Reactions

Lesson Description:

Chemists have classified chemical reactions in a number of ways. See the four most basic and combustion listed below.

Synthesis or Composition
A + B → AB
Example: H2(g) + Cl2(g) → 2HCl(g)
Decomposition
AB → A + B
Example: 2HgO → 2Hg + O2(g)
Single Replacement or Substitution
A + BC → AC + B
Example: Zn + 2HCl → ZnCl2 + H2(g)
Double Replacement or Exchange
AB + CD → AD + BC
Example: AgNO3 + KCl → AgCl (s) + KNO3
Combustion
Compound + Oxidant → Products and flame
Example: 2Mg + O2 → 2MgO + light and heat
Salt and sugar are soluble in water. Oil is insoluble in water. When small amounts of a substance dissolve, the substance is termed slightly soluble.

The water in the above cases is known as the solvent, which does the dissolving. The salt, sugar, and oil are the solutes, the stuff you're attempting to dissolve.

You'll see attempts to dissolve a number of solutes, both solid and liquid, in liquids. See the Procedure page for information on the chemical composition of all of these substances. Make predictions before each experiment.
Look for ways to predict solubility. Note the size, mass, composition and polarity of the substances. Polarity refers to the amount of separation of electrical charge in a molecule. Higher dielectric constant means greater polarity.
The neck's calibrations show 0.1 ml per large calibration mark and 10 microliters (μl) for the smaller marks. Microliters are 1,000 times smaller than milliliters.Some analog measurements are listed below.

Length: meter stick
Mass: triple-beam balance
Force: spring scale
Temperature: thermometer
Volume: graduated cylinder
In this lab, you'll measure distance, mass, temperature, force, and volume.
Measurement

Any measurement consists of two parts:
the value and
the units.

If you report a length as being 1.7, no one will know whether it's the size of a bacterium or a continent. Don't leave out the units.

Accuracy
Accuracy tells how good your measuring device is.
Does it measure correctly?

Precision
Precision is all about repeating measurements and getting the same value.
Try to measure the height of someone who won't stand still.