Which scenarios are examples of physical changes? Check all that apply.

1-Wood is burned in a campfire and is turned into ash and smoke.
2-Silicon is cut into tiny pieces for computer chips.
3-Lead is melted to form pellets.
4-Liquid water freezes to form ice.
Yeast turns sugar into energy, water, and carbon dioxide gas.

m=9

step-by-step explanation:

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o