Chemistry Experimentswith Dr. Doumit

The Explosion2H2 (g) + O2 (g) ---------------- 2H2O (g)An example of a combustion reaction!Hydrogen Balloon ignited by a flame.

Properties of CopperPennies are coated with copper. Which are physical properties of copper and which are the chemical properties? What are two additional properties?

Observing Chemical Change

Breaking and Making BondsDescribe what happens to the bonds in each of the steps as oxygen reacts with magnesium.

Observing Chemical Change

Describing Chemical Reactions

Chemical FormulasThe formula of a compound identifies the elements in the compound and the ratio in which their atoms or ions are present. What are the missing chemical formulas in the table?

Modeling a Chemical EquationLike a skateboard, a chemical equation has a basic structure. How many complete skateboards can be made from the parts pictured?

Describing Chemical Reactions

Molecules of nitrogen (N2) and hydrogen (H2) react to form ammonia (NH3). How many H2 and N2 molecules are needed to yield two molecules of NH3?

Describing Chemical Reactions

Balancing Chemical EquationsWhat are the four steps in balancing chemical equations?

Describing Chemical Reactions

Step 1 Step 2

Step 3 Step 4

Describing Chemical Reactions

Types of ReactionsWhat is each type of reaction represented?

Activation EnergyA chemical reaction needs a push to the “top of the mountain” to get started. Where has enough activation energy been added to start the reaction?

Controlling Chemical Reactions

Graphs of Exothermic and Endothermic ReactionsEach of the graphs shows the amount of energy before and after the reaction. On each graph, determine whether energy is absorbed or released.

Controlling Chemical Reactions

CatalystsAdding a catalyst speeds up a chemical reaction. How would the energy graph change for the same chemical reaction if a catalyst were used?

Controlling Chemical Reactions

Crookes Tube (Cathode ray tube)

Deflection of electrons on a magnetic field.

If a magnetic field is placed across the beam (with the north pole indicated by tape in front), the beam is deflected downward as shown (by Steve Grabowski) in Figure 110-3.

If the magnetic field is reversed (so that the north pole is in the back) the beam is deflected upward as shown in Figure 110-4.

Why it WorksA magnetic field does not exert a force on a

stationary electron. However, a magnetic field does produce a force on a moving electron. The electron's motion, the magnetic field, and the force are all at right angles to each other.

The PointProperties of the electron can be determined by

observing its behavior in electric and magnetic fields.The electron is negatively charged. The force

produced by a magnetic field on a moving beam of electrons can be described by the right-hand rule, in which the thumb indicates the direction of the force, the index finger indicates the direction of the motion of the electrons, and the rest of the fingers indicate the direction of the magnetic field.

Careful analysis of electric and magnetic fields on an electron beam determines the charge to mass ratio of the electron.