reactions

is the energy added (endothermically) to the reactant side that ensures that there is an “effective” amount of energy present to start the reaction. It is essentially the absorbed energy used to break bonds so the rearrangement of atoms is possible. Think about striking a match. If you give it a moment of thought… anything after “AE” that _________the number of collisions will simply __________the rate of the reaction. Increasing the __________________, ____________ (for gases only), or the _____________________(amount) of reacting particles will make effective collisions more likely to occur because collisions will occur more frequently. However, increasing the _______________________also increases the ___________ of those collisions, so it is by far the most important variable when discussing Kinetics (which we do, at length, a little later this year).

They are ______ _____ (dissolved) ions that can conduct an electrical current. The picture above is a similar setup to our classroom demo using the light bulb. The two electrodes are “connected” by the electrolyte solution. BUT which electrolyte is the best when compared? Use table F and our knowledge of formula writing to compare CaCl₂ and NaCl. Always make sure they are soluble compounds first… and these are. Using Table F we can summarize by saying that the sodium is a group 1, that ion is always soluble! The halides dissolve well with a few exceptions. Calcium is NOT an exception for the solubility of halides. Which compound would be better at conducting if we put equal amounts of both in separate solutions?

A precipitate is a ______ that forms as a product in a __ reaction. It “falls” to the bottom of the beaker much like rain (precipitation) falls from the clouds. In the example below we see reactants, one with a ____ ion, and the other with a group metal ion… both are soluble compounds since there are no exceptions to solubility for those ions on Table F. They make clear solutions because the compounds have dissolved completely. AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq) 🌟 The precipitate forms because the compound, AgCl, is ________ in water. You will find the Cl- ion on the lower left in the “_________”, which are predominantly soluble. Ag+, however, is listed as an ____________ and when combined with a halide ion will not dissolve. It is an insoluble precipitate and will settle to the bottom.

The number of atoms on the reactants side _____________ the number of atoms on the products side. ● Use ___________ to balance chemical equations atom for atom (mass is conserved in this multiplication game!). ● Tip - Save _________ atoms for last when balancing equations and remember the diatomic BrINClHOF elements.

by the reaction above. _______ belongs on the ________side of the chemical equation with the _________ A + B → C + __________ This means that the reactants will have _______energy than the products… which means some energy was _________during the reaction. From where ? The ____________! The negative sign tells heat flow is out of the system. Example: CH4 + 2O2 → CO2 + 2H2O + 890 kJ 🌟Never put a minus sign in any chemical reaction ! … by placing heat on the right with the products as a positive value the reader understands that heat is being released (produced) and that the amount of energy on both sides of the reaction is ________.

by the reaction above. _______ belongs on the ______ side of the chemical equation with the _________. A + B + _______ → C This means that the products will have_______energy than the reactants … which means that energy was ____________ during the reaction. From where ? The ______________! The positive sign tells us the direction of heat flow is into the system. Example: H2 + I2 + 53kJ → 2HI By placing the heat value on the left side with the reactants this chemical equation has __________amounts of energy on both sides of the equation and energy has been________________.

Have a close look at the right side of Table I. The +, - signs indicate which way energy (kJ) is “flowing”. If the change in heat is a negative value it means heat energy is ______________by the chemical “system” and the surroundings will feel _________. Sometimes the surroundings are a beaker or the water in the beaker. If the change in heat is a positive value it means heat energy is ______________by the chemical “system” and the surroundings will feel __________. We cannot “feel” the chemistry, only the surroundings.

2. Reactions always follow the same format where Reactants Yield Products. The word “yields” is indicated by and replaced by an arrow → , or a double headed arrow when a reaction is reversible ↔. Reactions also show that all mass, all energy, and all charge is CONSERVED during chemical reactions. Example : CH4 + 2O2 → CO2 + 2H2O + 890.4 kj The example has 1 C, 4 H, and 4 O on both sides of the chemical equation. Some of the energy initially located in the bonds on the reactant side has been released into the surroundings on the product side. Every electron is accounted for as the atoms have been rearranged into new combinations. 3. There is always an exchange of heat in every chemical reaction. This implies that exchange of heat is either absorbed (endothermic) into the chemical system from the surroundings or released (exothermic) from the chemical system into the surroundings.