Chemistry Exam 1

What is chemistry?

The science that seeks to understand the behavior of matter by studying atoms and molecules.

What is matter?

Anything that occupies space and has mass.

What is a molecule?

A specific geometrical arrangement of atoms.

What is an atom defined as?

Subatomic particles that are the fundamental building blocks of ordinary matter.

What is a hypothesis?

A tentative interpretation of observations.

What is an experiment in the scientific approach?

A highly controlled procedure designed to generate observations that confirm or refute a hypothesis.

What is a scientific law?

A brief statement that summarizes past observations and predicts future ones.

What is a scientific theory?

A model for the way nature is that tries to explain why nature does what it does.

What is a substance?

A specific instance of matter.

What is the state of matter?

The physical form of matter.

What is composition in the context of matter?

The basic components that make matter up.

What is a crystalline solid?

Atoms or molecules are in patterns with long-range, repeating order.

What is an amorphous solid?

Atoms or molecules do not have any long-range order.

What is a chemical change?

A change that alters the composition of matter.

What is distillation used for?

Separating liquids with different boiling points.

What happens to the most volatile component during distillation?

It boils first.

What happens to the vapor during distillation?

It is cooled and collected as pure liquid.

What is filtration used for?

Separating a liquid and a solid mixture.

In filtration, what does the filter paper do?

It traps the solid.

What is a chemical change?

A change that alters the composition of matter.

What is a chemical property?

A property a substance displays only by changing its composition via a chemical change.

What is a physical property?

A property a substance displays without changing its composition.

What is a physical change?

A change that alters only the state or appearance, but not composition.

How do you convert Celsius to Kelvin?

K = ºC + 273.15

How do you convert Celsius from Fahrenheit?

ºC = (ºF − 32) ÷ 1.8

Larger than 1: What is the multiplier for the prefix "kilo" (k)?

1,000 (10³).

What is the multiplier for the prefix "mega" (M)?

1,000,000 (10⁶)

What is the multiplier for the prefix "giga" (G)?

 10⁹

What is the multiplier for the prefix "tera" (T)?

 10¹²

Smaller than 1: What is the multiplier for the prefix "deci” (d)?

10⁻¹

What is the multiplier for the prefix "centi” (c)?

10⁻²

What is the multiplier for the prefix "milli” (m)?

10⁻³

What is the multiplier for the prefix "micro” (µ)?

10⁻⁶

What is the multiplier for the prefix "nano" (n)?

0.000000001 (10^-9)

What is the multiplier for the prefix "pico" (p)?

10⁻¹²

What is 1 s.f. in scientific notation?

1 × 10²

What is 2 s.f. in scientific notation?

1.00 × 10²

What is 3 s.f. in scientific notation?

100 × 10²

When should you round?

Always last, never while you’re solving it.

If the digit dropped is greater than 5, what should you do (s.f.)?

Round up

If the digit dropped is lower than 5, what should you do (s.f.)?

Round down

If the digit dropped is equal to 5, what should you do (s.f.)?

Even result; nothing.

What are non-zero digits considered? What’s an example?

All of them are considered significant. Example: 123, 0.123

What are captive zeros? What’s an example of it?

Zeros between non-zeros. They’re considered significant. Example: 509, 0.109

What do leading zeros tell us? Are they significant? What’s an example of it?

They are zeros in front of non-zeros. They’ll tell us where the decimal point is, and you’ll still need to write them. No, they’re not considered significant. Example: 00308, 0.00405

What are trailing zeros? What’s an example of it?

Zeros after non-zeros AND after decimals are significant. Example: 55.00

What is volume defined as?

Volume is an extensive property.

What is density defined as?

Density is an intensive property.

How are scientific measurements reported?

Every digit is certain except the last, which is estimated.

What is random error?

Error that has an equal probability of being too high or too low.

What is systematic error?

Error that tends to repeatedly be either too high or too low.

What is the first step in problem solving?

Identify the starting point, which is the given information.

What is the second step in problem solving?

Identify the end point, which is what you want to find.

What is the third step in problem solving?

Devise a plan to get from the starting point to the end point.

How do you convert 26.2 mi to m using dimensional analysis?

Multiply 26.2 mi by the conversion factor (1609.3 m / 1 mi).

How is 4.5 ns expressed in scientific notation with base units?

4.5 x 10^-9 s

How is 35 µm expressed in scientific notation with base units?

3.5 × 10^-5 m

How many significant figures are in 0.000012 m?

2

How many significant figures are in 8.123 x 10^4 km?

4

How many significant figures are in 3,127 s?

4

How many significant figures are in 1,280 s?

3

How do you convert 3289 cm³ to L?

Convert cm³ to mL, then mL to L.

1. Convert cm³ to mL:    Since 1 cm^3 = 1 mL, 3289 cm³ is equal to 3289 mL.

2. Convert mL to L: Since 1000mL = 1L, divide the value by 1000: 3289 mL x 1L/1000 mL = 3.289 L. Therefore, 3289 cm³ equals 3.289 L.

When is dimensional analysis supposed to be used?

When you’re converting units that don’t share a common base. For example, ft to in, or kg to lbs

What does the metric system allow us to do?

Convert units that share a common base. For example, mL to L, or kg to mg.

What are some base units we commonly see?

Grams, meters, and liters

What is a trick you can use with conversion factors? (pt. I)

Always place 10^x with the base unit (g, m, L).

What is a trick you can use with conversion factors? (pt. II)

Always place 1 with the different unit (kg, cm, mL).

What is the basic setup for a unit-conversion problem?

Start with the number and unit you are given, then multiply by a conversion factor.

Where should the unit I WANT go in the conversion factor?

The unit you WANT goes on the TOP.

Where should the unit I HAVE go in the conversion factor?

The unit you HAVE goes on the BOTTOM.

What is the general setup for a unit conversion?

Given unit × (wanted unit / given unit) = answer in the wanted unit.

What if I have to make multiple conversions?

Keep adding conversion factors until the units you don't want cancel and you are left with the unit you need.

What does a multiple-conversion setup look like?

Given unit × (new unit / old unit) × (new unit / old unit) = final unit.

Example of a multiple-conversion setup: How would I set up 2.5 km → cm?

2.5 km × (10³ m / 1 km) × (10² cm / 1 m)

How do I convert 5 kg to g?

Set it up as:

5 kg × (10³ g / 1 kg)

The kg cancels, leaving:

5 × 10³ g = 5,000 g

What are the basic metric conversion paths for length, mass, and volume?

Length: km → m → cm → mm
Mass: kg → g → mg
Volume: kL → L → mL

Are connecting units required?

Not always. You can solve the problem if you know the direct relationship. Ex:1 km = 100,000 cm. You could do km × (100,000 cm / 1 km), and km cancels.

How many centimeters are in 1 inch?

1 in = 2.54 cm

How many kilometers are in 1 mile?

1 mi = 1.609 km

How many yards are in 1 meter?

1 m = 1.0936 yd

How many meters are in 1 mile?

1 mi = 1609.3 m

How many inches are in 1 foot?

1 ft = 12 in

How many feet are in 1 yard?

1 yd = 3 ft

How many pounds are in 1 kilogram?

1 kg = 2.205 lb

How many grams are in 1 pound?

1 lb = 453.6 g

How many grams are in 1 ounce?

1 oz = 28.35 g

How many cubic centimeters are in 1 milliliter?

1 mL = 1 cm³

How many quarts are in 1 liter?

1 L = 1.057 qt

How many quarts are in 1 gallon?

1 gal = 4 qt

How many cubic decimeters are in 1 liter?

1 L = 1 dm³

How many liters are in 1 cubic foot?

1 ft³ = 28.317 L

How many seconds are in 1 hour?

1 hour = 3600 sec

Convert 5.0 mi to km.

5.0 mi × (1.609 km / 1 mi) = 8.045 km

Convert 10 ft to inches.

10 ft × (12 in / 1 ft) = 120 in

Convert 2.5 kg to lb.

2.5 kg × (2.205 lb / 1 kg) = 5.5125 lb

How can a mixture be separated?

They can be separated into their component parts through physical means. For example, A sample of beach sand contains sand particles of different colors, small pebbles, and also shells. Each component contains different metals and minerals. The pebbles and shells can easily be separated from the sand.

How can a pure chemical substance be separated?

Pure physical substances require chemical or nuclear reactions to separate them. They can be further divided into elements or compounds.

Mixtures can be what?

Either heterogeneous or homogeneous.

What is a good way to remember the order of metric prefixes from 10³ to 10¹²?

Kids (Kilo) Make (Mega) Good (Giga) Tech (Tera)

What is a good way to remember the order of metric prefixes from 10⁻² to 10⁻¹²?

Ducks (Deci) Can (Centi) Make (Milli) Micro (Micro) Nests (Nano) Perfectly (Pico)