Question

1. how are elements and compounds similar? how are they different?
2. what are the key differences between mixtures and pure substances?
3. classify each of the following as either a heterogeneous (het) or homogeneous (hom) mixture:

a. lemonade with pulp het
b. tap water homo
c. pure or filtered water
d. ocean water homo
e. beach sand
f. steel (an alloy of iron and carbon)
g. air homo
h. raisin bread het
i. vinegar (acetic acid and water)
j. cheerios in milk het
k. gasoline homo
l. sweet tea homo
m. ranch dressing het
n. orange crush soda homo

1. when 50 ml of ethanol is mixed with 50 ml of water, a solution forms (ethanol, a type of alcohol soluble in water.) after mixing, the volume of the final solution is found to measure less than 100 ml. is this surprising? what would you expect the final volume to be? propose a hypothesis for this observed behavior. (hint: consider what you know about the space between particles in liquids)

Explanation:

Step1: Answer question 3

Elements and compounds are both pure substances. Elements consist of only one - type of atom, while compounds are made of two or more different types of atoms chemically combined.

Step2: Answer question 4

Mixtures are composed of two or more substances physically combined, and their composition can vary. Pure substances have a fixed composition, either an element (one - type of atom) or a compound (fixed ratio of different atoms).

Step3: Answer question 5

a. Lemonade with pulp is heterogeneous (Het) as the pulp is visibly distinct.
b. Tap water is homogeneous (Hom) as it appears uniform.
c. Pure or filtered water is homogeneous (Hom) as it is a single - phase substance.
d. Ocean water is homogeneous (Hom) as it appears uniform at a macroscopic level.
e. Beach sand is heterogeneous (Het) as it contains different sized and types of particles.
f. Steel (an alloy of iron and carbon) is homogeneous (Hom) as it has a uniform composition.
g. Air is homogeneous (Hom) as it is a uniform mixture of gases.
h. Raisin bread is heterogeneous (Het) as raisins are distinct from the bread.
i. Vinegar (acetic acid and water) is homogeneous (Hom) as it is a solution.
j. Cheerios in milk is heterogeneous (Het) as cheerios and milk are distinct.
k. Gasoline is homogeneous (Hom) as it is a uniform mixture of hydrocarbons.
l. Sweet tea is homogeneous (Hom) as it is a solution.
m. Ranch dressing is heterogeneous (Het) as it may have suspended particles.
n. Orange crush soda is homogeneous (Hom) as it is a solution.

Step4: Answer question 6

It is surprising that the volume of the final solution of 50 mL ethanol and 50 mL water is less than 100 mL. We would expect the final volume to be 100 mL if volumes were additive. Hypothesis: The particles of ethanol and water are of different sizes, and the smaller ethanol particles can fit into the spaces between the water particles, resulting in a lower - than - expected total volume.

Answer:

1. Elements and compounds are both pure substances. Elements have one - type of atom, compounds have different types of atoms chemically combined.
2. Mixtures are physically combined with variable composition, pure substances have fixed composition (element or compound).
3. a. Het; b. Hom; c. Hom; d. Hom; e. Het; f. Hom; g. Hom; h. Het; i. Hom; j. Het; k. Hom; l. Hom; m. Het; n. Hom
4. Surprising. Expected volume: 100 mL. Hypothesis: Ethanol particles fit into water - particle spaces, reducing total volume.