CHEM LAB

_______ is a very important quantity in chemistry because it gives an idea of how tightly the matter is packed in a substance. Every substance on earth has its own characteristic _______

Density

Density = ______ / ______

Density = mass/volume

Percent error

Percent error = |(experimental value-accepted value) / accepted value | * 100

Beakers and flasks are marked to indicate ______ measurements of volume while graduated cylinders, calibrated pipets, and volumetric flasks are used for more ____ and ____ measurements of volume

approximate more accurate and precise

Always read the ________ of the meniscus.

bottom

What is the difference between a Top-Loading Balance and an Analytical Balance?

(REWRITE ANSWER IN OWN WORDS) Top-loading balances measure mass to the nearest 0.01 g or 0.001 g whereas, analytical balances are more sensitive measuring mass to the nearest 0.001 g or 0.0001 g.

this beaker can be filled to the nearest (ADD MORE OF THESE)

+- 10mL

What are the two types of laboratory balances?

- Top-Loading Balance - Analytical Balance

GIVE THE STEPS TO SOLVE: Example: A piece of metal was measured to have a mass of 195.368 grams. The volume of the metal was measured by liquid displacement (initial volume = 50.00 mL and final volume = 89.08 mL). Determine the identity of the metal from the metals listed below base on the experimental density.

1. Calculate the volume of the metal by subtracting the initial volume of liquid from the final volume of liquid to determine the amount of liquid that was displaced. This will give the volume of the metal. volume of metal = volume_f - volume_i = 89.08 mL - 50.00 mL = 39.08mL 2. Calculate the density of the metal by dividing the metal's mass by its volume. density = mass/volume d = 95.368 g/39.08mL = 4.97 g/mL

SOLVE W/ STEPS: Example: The density of water was determined experimentally by measuring the mass and volume of water. Three trials were completed giving the following data: Trial 1: 0.9975 g/mL, Trial 2: 0.9902 g/mL, and Trial 3: 0.9899 g/mL. Calculate the standard deviation of the experimental densities

1. FIND MEAN: mean (average) = Σexperimental values/n , where n = number of values mean = (0.9975g/mL + 0.9902 g/mL + 0.9899 g/mL) / 3 x = 0.9925 g/mL 2. FIND STANDARD DEVIATION: S = sqrt( ((x_1 - x)^2 + (x_2 - x)^2 + (x_3 - x)^2 ...) / n-1 ) ---> x_1 = 0.9975 g/mL (Trial 1); x_2 = 0.9902 g/mL (Trial 2); x_3 = 0.9899 g/mL (Trial 3); x = mean S = sqrt( ((0.9975 - 0.9925 g/mL)^2 + (0.9902 - 0.9925 g/mL)^2 + (0.9899 - 0.9925 g/mL)^2) / 3-1 ) S = sqrt( ((0.0050)^2 + (-0.0023)^2 + (-0.0026)^2) / 2 ) standard deviation = +- 0.0043

_____ refers to how close the measured value is to the actual value and _____ refers to how close a series of measurements are to one another or how reproducible they are.

Accuracy, precision

______ error is defined as the difference between an experimental value and the actual or accepted value. This is used to indicate the accuracy of the measurement. ______ error is often used by chemists to report the difference between a measured or experimental value and a true or exact value.

Experimental error Percent error

_____, _____, and _____ are properties of matter that can be observed or measured

Mass, volume, and density

SOLVE: Example: The density of distilled water at 17.5 °C was determined experimentally by measuring the mass and volume of the water. The mean experimental density was calculated to be 0.9975 g/mL. The accepted density of water at 17. 5 °C is 0.998686 g/mL. What is the percent error in the experimental density?

Percent error = |(experimental value-accepted value) / accepted value | * 100 Percent error = |(0.9975 g/mL - 0.998686 g/mL) / 0.998686 g/mL | * 100 Percent error = | -0.0012 | * 100 Percent error = 0.12%

_______ measures how widely spread data points are. The precision of a set of measurements can be determined by calculating this for a set of data where n-1 is the degrees of freedom of the system.

Standard deviation

_____ is the measure of space that is taken up by matter and is usually measured in liters (L) or milliliters (mL).

Volume

In gaseous matter, atoms and molecules are widely spaced and can spread out indefinitely. Therefore, gases have no definite volume and no definite shape. If confined, gases will expand to fill its container.

add def.

In liquid matter, atoms or molecules are still closely packed together, but are not in a regular arrangement and can move past one another. Therefore, liquids have an indefinite shape and conform to the shape of the container that it is placed in.

add def.

Since atoms and molecules in the gaseous state have a lot of space between them, they are free to move relative to each other and can be compressed.

add def.

Top-loading balances measure mass to the nearest 0.01g or 0.001 g whereas, analytical balances are more sensitive measuring mass to the nearest 0.001 g or 0.0001 g.

add def.

on a laboratory balance, how many digits on the digital display are significant and should be recorded?

all digits seen

In SOLID matter, atoms/molecules are ______ packed together in a fixed place and therefore, can only ______. Solids have a ______ shape and _________________ to the container it is placed in.

closely packed together can only vibrate definite shape + do not conform to the container

Solid and liquid matter cannot be ________

compressed

The _______ of a substance is the ratio of its mass (m) to its volume (V) and is usually represented as g/mL.

density (d)

sound, light, and heat are examples of what?

energy

The more variation in the measurements, the ______ the standard deviation will be. a. larger b. smaller

larger

The _____ of an object is the measure of the amount of matter within it and is usually measured in grams (g)

mass

Anything that occupies space and has mass is...

matter

In general, if you can touch something, it is ________.

matter

water, hair, paper, rubber, ink, potatoes, teeth, and air are all examples of what?

matter

Our universe is made up of two things: _____ and ______.

matter and energy

In making observations, how many uncertain digits should be reported?

one

convex meniscus

sides curve downward

concave meniscus

sides curve upward

Matter can exist in three different states: _______, ________, and ________.

solid, liquid, and gas

Scientific measurements are reported so that every digit is certain except the ______, which is estimated.

the last