Chapter 24: Chemical Reactions

Chemical Reactions evidence of chemical reactions

Section 1: Chemical Changes Chemical reaction: a change in which one or more substances are converted into new substances The substances that react together are called reactants The new substances produced are called products The mass of the reactants before the reaction MUST equal the products, according to the law of conservation of mass

Chemical Reactions glycerol and potassium permanganate dehydration of sugar sodium acetate

Describing Chemical Reactions French chemist Antoine Lavoisier discovered this law in the late 1700s. He heated 10 grams of mercury (II) oxide in a sealed container The compound bubbled and changed from a red powder (HgO) to a silver liquid (Hg) He had 9.3 grams of mercury, and 0.7 grams of oxygen (9.3 + 0.7 = 10.0 g) Therefore, matter is conserved in a chemical reaction video

Chemical Reactions pharaoh's snake Chemiluminescence phosphorus in oxygen

Writing Equations Just like we write chemical formulas to save space, we can write chemical equations to show a chemical reaction 2HgO (s)  2Hg (l) + O2 (g) 2 units of solid mercury (II) oxide produce 2 units of liquid mercury and 1 unit of oxygen gas The 2’s in front of the HgO and the Hg are called coefficients The letters in ( ) tell us the state of matter (aq) means “dissolved in water”

Chemical Reactions http://dsc.discovery.com/videos/mythbusters-diet-coke-and-mentos.html scifun.org

Cd(NO3)2(aq) + H2S(g)  CdS(s) + 2HNO3(aq) Review Questions Answer these questions for tomorrow: Cd(NO3)2(aq) + H2S(g)  CdS(s) + 2HNO3(aq) Identify these items: Reactants Products Names States of matter If you started with 15 grams of reactants, how much product should you get? What might happen if chemical reactions did not obey the law of conservation of mass?