Endothermic reactions

Endothermic reactions draw heat in from their surroundings

*gain heat

*have a positive delta H

*have energy as a reactant

*ex: photosynthsis

reactants + energy ---> products

Le Chatelier's principle

" If a system at equilibrium is disturbed, the system shifts to counter

the effect of the disturbance"

Le Chatelier is saying that equilibria Resists change.

Pressure and Le Chatelier's Principle

count the number of gas molecules on each side of the balanced chemical equation.

* a shift towards more gas molecules INCREASES pressure.

*a shift towards fewer gas molecules DECREASES pressure.

remember: if the numbers of gas molecules is equal, then changes in pressure has no effect.

Calorimetry & Q=mcDELTA T

In one of our past units we learned about calorimetry. calorimetry is the measurement of heat flow.

the measurements are made inside an insulated apparatus called a calorimeter.

to calculate heat energy we used this formula Q=mcdeltaT.

m= the mass of the matter being measured.

c=specific heat. the amount of heat energy required to raise 1g of a substance to 1*c. (cal/g*c or J/g*c)

remeber Q=mcdeltaT can only refer to ONE object

swich up the formula to find certin variables---->

Q=mcdeltaT

m=Q/cdelatT

c= Q/mdeltaT

delta T=Q/mc

lean more about Q=mcDELTA T ***

DAVID WEB!

today in class we had two visitors, David Webb and his assistant. When i first walked in i noticed a bunch of random things over it the lab. everything from coca cola bottles and weights to balloons. through the class David Webb picked voulenteers form out class and had them participate in his labs. all the labs had something to do with the atmosphere. in a lot of his expiriments he used a vacuum. not a vacuum used to clean your house but a chemistry vacuum. the vacuums showed us how objects act in different atmospheres with different air pressures. i thought it was really cool to learn about how things happen in space and why humans wouldnt be able to live there. Overall it was probally one of the coolest days in chemistry.

LEAN MORE ABOUT VACUUMS**

exothermic reactions :)

Exothermic reactions are reaction give heat off to their surroundings. the energy needed for the reaction to occur is less than the total energy released

*release heat
*have a negative delta H
*and have energy as a product

*ex: combustion

reactants → products + energy