OrderIng and Supplies for the Water Lab
SUPPLIES: Properties of Water
EQUIPMENT PER GROUP
- BROWNIAN MOTION OBSERVATIONS
- Microscope 250X or more
- Microscope slides and coverslips
- India ink: must be fresh. Black India ink consists of a suspension of carbon particles.
- TEMPERATURE EFFECTS ON SURFACE TENSION, VISCOSITY, ADHESION
- One large foil cassarole dish (c 9 inches diameter) to be used as a temperature regulated waterbath.
- One thermometer that includes 0°C to 100°C
- One Sharpie marker
- One 10 ml pipette graduated in 0.1 ml
- One Viscometer
- Clear, flexibile vinyl tubing 3 ft or 1 meter long. 5/16 inch inside diameter.
- 2 spherical 10 mm diameter plastic beads
- 1 spherical 6 mm diameter plastic beads
- Plug one end of the tubing with a 10 mm bead. Be sure that the drilled hole is sideways in the tubing, otherwise you will have a leak.*
- Fill tube to the rim with water or other fluid to be tested.
It is good to use a fluid that has been boiled to expel dissolved air.
- Drop in the smaller bead (after filling its drilled hole with water - you don't want an air bubble inside!) or, if the liquid to be tested varies little in viscosity, use a circle of sequin.
- Plug the other end of the tubing by slowly working the other 10 mm bead into the tube so that no air is trapped.
- The viscometer is complete. (See student directions as to how to use.)
- SURFACE TENSION
One of the most common ways thought to assess the effect of temperature on surface tension is to count the number of drops in a constant volume. This is true, except that most situations do not have the rigorous conditions needed to maintain the temperature of the delivery container. The results are usually so imprecise as to be nearly random, because, for example, the small drop's exposure to the air causes rapid evaporative cooling. Thus in the following two exercises the temperatures are much more likely to remain known.
- Coin Experiment
- One coin (5¢ or 5p or larger denomination)
- One oiled cloth for each group. Use either motor oil or cooking oil. Need little cloths? Cut up one of the DRY cotton cloths into 16 squares. By applying a minutely thin film of oil on the coins will keep the coin a constant entity from one run to the next.
- "Needle" Experiment
- Set of "needles" of various diameters as described in main handout.
Gauged straight, steel wires can be bought at many hardware stores and then cut to specific lengths.
Recommend: the thicker the wire, the longer the piece.
Lay them out and photocopy a set; indicate the diameters on the copy. Students can then match up lengths of any wayward wires.
|Examples of Steel ("Music") Wires from ACE Hardware
|Diameter (inches)||Rel. mass/length||Cut Length (mm)||ACE Stock No.
- Plastic coated paper clips to be reshaped and used to float the above wires.
- One half of a petri plate (to serve as a boat)
- One hot plate
- ADHESION EXPERIMENT
- Swatches of various fabrics. They should be 100% pure material - pure cotton, pure wool, pure silk, rayon, nylon, polyester, linen, etc. And they should be labelled with marking pen. Also include small pieces of chamois and thin slices of any sort of sponge.
- Scale or Balance accurate to 0.1 gm
- Zip-Lok plastic bags (gallon size)
- Graph paper collection.
Consider using page 73 in the graph book:
Place it sideways. Across the long side fit inthe temperatures from 0 to 100°C
Along the upwards short side, number in the wires' gauges.
| TOP OF PAGE | Handout of Water Protocols |
* Teacher, it is not horrible to personalize statements such as "otherwise you will have a leak." Yes, it is literally incorrect because YOU are not the one with a leak - the tube is! But even Nobel laureates have been known to get so excited about their work that, for example, when bacteriophages were first discovered, one future Nobel prize winner ran in to tell his colleagues: "We have lysed." As a teacher, you want to inculcate such a sense of pride in your students' minds that they consider their work part of themselves and vice versa. So it is suggested you tell them that personal identification with results is your own class's secret way of saying things. Build esprit d'corps! The community of science!