Which is longer, a string that measures 0.25 km or a string measuring 101 mm?

Since a km is equal to 1,000 m and a mm is only equal to 0.001 m, the string measuring 0.25km is longer.

Convert 34.5 kL into L.

34 5kl  x  1000L   =  34,500L

   1            1kl

Convert 0.001400 into scientific notation.

1.400 x 10^-3

Two students measure the length of a 2.1-meter object. The first student measures the length to be 2.8123 m. The second measure the length to be 2 m. Which student was more precise? Which student was more accurate?

Assuming both students reported the proper number of significant figures, the first student was more precise (because there are more places to the right of the decimal), but the second student was more accurate (because it is closer to the correct value).

This is a two-step conversion, since we know of no 

relationship between kg and mg. Thus, we must first convert kg to g and then convert g to mg. We’ll 

do this on one line:

.00045kg x   1000g   x   1mg     

    1              1kg        0.001g       

450mg is the final answer

A young girl puts a leash on her dog, but she can.t get the dog to move. She pulls and pulls and pulls but the dog will not budge. Did the girl do any work?

The girl did no work. Motion must occur for work to be done.

Classify each of the following as having either potential or kinetic energy, or both:

a. A pile of fire wood 

b. Light

c. wind

d.gallon of gasoline

a. A pile of fire wood has potential energy in it because all matter has stored energy.

b.  Light has no matter, but it does move, so it has kinetic energy.

c.  Wind is moving air, so it has kinetic energy. Air also has mass, however, so it has stored

energy as well. Thus, it has both.

d.  The gasoline is matter, so it has potential energy

What are the four assumptions of Dalton.s atomic theory.

1. All elements are composed of small, indivisible particles called “atoms.”

2. All atoms of the same element have exactly the same properties.

3. Atoms of different elements have different properties.

4. Compounds are formed when atoms are joined together. Since atoms are indivisible, they can only join together in simple, whole-number ratios.

How can you experimentally determine whether a compound is ionic or covalent?

A compound is ionic if, when dissolved in water, it conducts electricity. If it does not conduct electricity, the compound is covalent.

How can you determine from the periodic chart whether a compound is ionic or covalent?

If a compound has a metal in it, it must be ionic. If it has no metals, it is covalent.

Which of the following molecules are covalent?

a. CO2

 b. CaBr2

c. KCl

d. C3H8

All elements that lie to the left of the jagged line on the chart are metals, while all elements to the right of the jagged line are nonmetals. A molecule is covalent only if it has no metals in it. Thus, CO2 and C3H8 arecovalent.

If a liquid goes through a phase change and all you know is that the molecules slowed down and moved closer together, what phase did the liquid turn in to?

Since molecules move slower and are closer together in the solid phase compared to the liquid phase, the liquid must have turned into a solid.

For the following compounds, if the name is given, write its formula. If the formula is given, 

write its name.

a. diphosphorus hexaoxide

b. PH3

c. nitrogen dioxide

d. CaS

a. P2O6 

b. phosphorus trihydride

c. NO2

d. calcium sulfide

Classify the following as an element, compound, homogeneous mixture, or heterogeneous mixture.

a. A fruitcake

b. A bottle of CH4O

c. A pile of carbon powder

d. Sugar dissolved in water

a. heterogeneous mixture

b. compound

c. element

d. homogeneous mixture

Classify the following as physical or chemical changes:

a. A priceless vase is shattered.

b. Coal burns in a furnace.

c. Water freezes.

d. Iron rusts.

a. physical change

b. chemical change

c. physical change

d. chemical change

Balance the following equation:

HNO3 (aq) + Mg (s) → MgN2O6 (aq) + H2 (g)

2HNO3 (aq) + Mg (s) → MgN2O6 (aq) + H2 (g)

Balance the following equation:

C10H22 + O2 → CO2 + H2O

2C10H22 + 31O2 → 20CO2 + 22H2O

Balance the following equation:

CO2 (g) + H2O (l) → C6H12O6 (s) + O2 (g)

6CO2 (g) + 6H2O (l) → C6H12O6 (s) + 6O2 (g)