Is burning bread a chemical or physical change

Activity two: just lemons, inc. production here's a one-batch sample of just lemons lemonade production. determine the percent yield and amount of leftover ingredients for lemonade production and place your answers in the data chart. hint: complete stoichiometry calculations for each ingredient to determine the theoretical yield. complete a limiting reactant-to-excess reactant calculation for both excess ingredients. water sugar lemon juice lemonade percent yield leftover ingredients 946.36 g 196.86 g 193.37 g 2050.25 g just lemons lemonade recipe equation: 2 water + sugar + lemon juice = 4 lemonade mole conversion factors: 1 mole of water = 1 cup = 236.59 g 1 mole of sugar = 1 cup = 225 g 1 mole of lemon juice = 1 cup = 257.83 g 1 mole of lemonade = 1 cup = 719.42 g

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)

What is true for a substance that releases energy