Overview

The essential features of the density laboratory are 

described as follows starting from the lower left-hand corner of the laboratory and proceeding clockwise:

  • Balance. This is a top-loading balance used for weighing the solids and liquids. The Tare button can be used to zero out the balance or the mass of the beaker. Solids can be dragged directly from the wall and placed on the balance or they can be dragged from the cylinders. Liquids can also be transferred from the graduated cylinder directly to the beaker while the beaker is on the balance or on the table.
  • Reset Lab. The Reset Lab button is used to clean up the entire laboratory after an experiment or explosion.
  • Liquid Dispenser. The liquid dispenser is used to select liquids and dispense them into the selected graduated cylinders. A liquid is selected using the up and down arrows, the name of the liquid is shown on the LCD display, and the liquid is shown in the container. A graduated cylinder can be filled half-full or full by clicking on the ½ or Full buttons, respectively. Clicking on the Fill button dispenses the selected liquid.
  • Solids. Solids for the density experiments are selected by clicking and dragging the solid from the wall and placing it either inside a graduated cylinder or on the balance. A large collection of solids have been provided including a set of virtual solids.
  • Nozzle. The dispensing nozzle for the liquids can be moved to the various graduated cylinders either by clicking on the green arrows or by clicking on the copper pipe directly above the desired graduated cylinder.
  • Exit. The exit button allows users to return to the general laboratory.
  • Clipboard. Clicking on the clipboard gives access to 15 preset density experiments that are already predefined and ready to run. Be aware that access to these preset experiments can be turned off by the instructor. The clipboard also gives access to the assigned unknowns given by the instructor.
  • Lab Book. The lab book is used to record procedures and observations while performing experiments in the virtual laboratory. Data from the experiments can also be saved as links in the lab book where it can then be copied and pasted into an external spreadsheet program for further analysis. See the Lab Book section for more detail.
  • Drop Time. This LCD display is used to measure the time required for a solid to drop through the selected liquid. The time required for a solid to drop is a function of the viscosity of the liquid and the relative densities of the solid and liquid.
  • Graduated Cylinder Zoom. Clicking near the top of the graduated cylinder will bring up a new window showing a zoomed-in view of the graduated cylinder near the meniscus of the liquid. This window is used to closely observe and measure the volume of the liquid in the graduated cylinder. A separate window is opened for each graduated cylinder.
  • Drain. Clicking on the drain valve for a graduated cylinder will empty the liquid in the cylinder and dispose of the solid.
  • Solid Return. Solids can be returned to the wall by dropping them down the Solid Return hole.
  • Beaker. The beaker is used to hold any of the liquids contained in a graduated cylinder. Liquids are transferred to the beaker by dragging and dropping one of the graduated cylinders on the beaker, and the liquid from a beaker can be transferred back to any of the empty graduated cylinders in the same manner. The beaker and its contents can also be weighed on the balance.
  • Graduated Cylinders. The graduated cylinders are used to hold any of the liquids and to measure the volume of the liquid. The volume is measured by clicking on the top of the selected cylinder to bring up the zoom window and then reading the volume from the location of the meniscus. The graduation marks are spaced every 2 mL, and an accurate reading can be made to within 0.5 mL.
  • Drop Solids. When a solid is placed in a graduated cylinder, pins are used to hold the solid above the liquid. Clicking on the Drop button will lower the solid to the top of the liquid and then drop it. Whether the solid floats or sinks depends on the relative densities of the solid and liquid. The All button can be used to drop all the solids in all the cylinders simultaneously.

Selecting Liquids

The dispensing nozzle for the liquids can be moved to the various graduated cylinders either by clicking on the green arrows or by clicking on the copper pipe directly above the desired graduated cylinder. Use the Stockroom Tray to select a Liquid. Then use the liquid dispenser to dispense them into the graduated cylinders. A liquid is selected using the up and down arrows, which cycles through the possible liquids as shown on the LCD display, and the liquid is shown in the container when selected. A graduated cylinder can be filled half-full or full by clicking on the ½ or Fullbuttons, respectively. Clicking on the Fill button dispenses the selected liquid

Selecting Solids

Solids for the density experiments are selected through the Stockroom Tray for the cylinder or on the balance. A large collection of solids have been provided including a set of virtual solids. The diameter of each selected sphere is randomized, so volume measurements will need to be performed for each solid sphere.

The Balance

This is the top-loading balance used for weighing the solids and liquids. The Tare button can be used to zero-out the balance or the mass of the beaker. Solids can be dragged directly from the wall and placed on the balance or they can be dragged from the cylinders. Liquids can also be transferred from the graduated cylinder directly to the beaker while the beaker is on the balance or on the table.

The Graduated Cylinders

The graduated cylinders are used to hold any of the liquids, measure the volume of the liquid, and to measure the volume of liquid displaced when a solid is added. The volume is measured by clicking on the top of the selected cylinder to bring up the zoom window and then reading the volume from the location of the meniscus. The graduation marks are spaced every 2 mL, and an accurate reading can be made to within 0.5 mL. The liquid can be drained from the cylinder by clicking on the drain valve at the bottom.

When a solid is placed in a graduated cylinder, pins are used to hold the solid above the liquid. Clicking on the Drop button will lower the solid to the top of the liquid and then drop it. Whether the solid floats or sinks depends on the relative densities of the solid and liquid. The All button can be used to drop all the solids placed in all the cylinders simultaneously. The LCD display at the bottom is used to measure the time required for a solid to drop through the selected liquid.