CHEM 1LC DENSITY LAB

What is the main goal of the Density Lab?

determine the concentration of sugar in Gatorade by measuring its density and comparing it to a calibration curve made from standard sucrose solutions.

How do you find the mass of the solution?

Mass = mass of full flask (M2) − mass of empty flask (M1)

Why? To calculate the density of each solution.

Calculate Moles of Sucrose. Why?

What is the formula for molarity (M)? Why?

M = mass (g) / molar mass (342.2965)

M = 0.1007g/ 342.2965 g/mol = 0.0002943 mol

Why? To find concentration.

M = moles of solute (mol) / volume of solution (L)

M = 0.0002943/0.01000 L

Why? To know the exact concentration ([Sucrose]) for making a calibration curve.

How do you calculate moles of sucrose?

Moles = mass of sucrose (g) / molar mass (342.2965 g/mol)

Why? To determine molarity, which is used for plotting the calibration curve.

What is the volume of the standard sucrose solutions used

10.00 mL = 0.01000 L

What is the formula for density? Why?

Density = mass of solution (g) / volume of solution (mL)

Why? You're graphing density vs. concentration to create a calibration curve.

What is a calibration curve? What goes on the calibration curve axes

A graph of known sucrose concentrations vs. measured densities.Use it to: Estimate unknown [Sucrose] by plugging measured Gatorade density into the equation.

X-axis: [Sucrose] in mol/L

Y-axis: Density in g/mL

Sample Calibration Curve Equation

Density = 0.126 * [Sucrose] + 0.991 (R² = 0.999)

To find concentration from density:
[Sucrose] = (Density - 0.991) / 0.126

How to find sugar in Gatorade using density

1. Weigh empty flask (M1)

2. Fill with 10.00 mL Gatorade, weigh again (M2)

3. Density = (M2 - M1) / 10.00 mL

   • e.g., (20.1566 - 10.0000) g / 10.00 mL = 1.01566 g/mL

4. use calib curve

   • Density=0.126⋅[Sucrose]+0.991

   • [Sucrose]=Density−0.991​/0.126

5. plug density of gatorade

   • [sucrose] = 1.01566 - 0.991/ 0.126

   • 0.02466/0.126 = 0.19575 mol/L

How do you convert mol/L to g/L? Why?

g/L = sugar conc mol/L × molar mass
= 0.19575 mol/L × 342.2965 g/mol = 66.96 g/L
Why? Nutrition labels use grams, not molarity.

Compare to Nutrition Label

Label = 21 g per 360 mL = 21 / 0.360 = 58.3 g/L

How do you calculate percent error?

% Error = |Measured - Expected| / Expected × 100
= |66.96 - 58.3| / 58.3 × 100 = 14.8%

Why do we assume Gatorade has only sucrose?

To simplify calculations, even though real Gatorade has other sugars. It introduces slight error.

Which glassware is most precise? Why?

Volumetric flask: has one precise marking, resulting in more consistent data. Usually gives best R² value

Why does R² matter?

R² (coefficient of determination) tells how well your data fits the line. Closer to 1 = better fit.

Why tare the digital scale with weighing paper?

To subtract the paper's weight and measure only the sugar.

What equipment is used in this lab?

Volumetric flask, graduated cylinder, beaker, balance, DI water, funnel, stirring rod/spatula.

Basic Procedure Steps:

1. Gather glassware (VF, GC, or beaker) and DI water.

2. Rinse glassware with DI water.

3. Tare balance with weighing paper.

4. Weigh sugar and record mass.

5. Record mass of empty flask (M1).

6. Add sugar using funnel.

7. Add DI water until 10.00 mL line.

8. Mix to dissolve completely.

9. Weigh full flask (M2).

10. Mass of solution = M2 - M1

11. Density = mass / 10.00 mL

12. Plot [Sucrose] vs. density to create calibration curve.

How to Use Your Argumentation CER

Claim: The volumetric flask gives the most accurate sugar concentration result.

Evidence: It had the lowest percent error and the R² value was 0.999, the closest to 1 out of all the glassware tested. That shows a really strong fit between sugar concentration and solution density. Also, volumetric flasks are marked to 4 significant figures, which gives more precise readings.

Reasoning: Volumetric flasks are specifically designed to measure one exact volume really accurately. Since it has only one calibration line, there's less chance of error compared to beakers or cylinders with lots of markings.
A high R² value (like 0.999) means your data had a strong linear relationship between sucrose concentration and density — so it was consistent and reliable.
That also shows precision, because precision means your results are reproducible — they’re close to each other across multiple trials.

The low percent error shows accuracy — which means your measured value is close to the actual or expected value.

%error = | measured - actual | / actual x 100
So a lower % error = more accurate results.
And the 4 sig figs on the flask help make those results better because they allow for smaller rounding errors.