Science

Properties of Matter Lab

Purpose:

To observe how a fluid cornstarch solution reacts to changes in temperature and pressure.

Materials:

·

· Clear plastic cup

· Newspapers

· Crushed ice

· Hot water

· Watch or clock

· Spoon

· Measuring cups

· Cornstarch

· One bowl deep enough to hold the plastic cup

Procedure:

1. Cover your kitchen table or counter with the newspaper to help make clean up easier.

2. Add 1 cup of cornstarch to ½ cup of water in the plastic cup. Stir with the spoon until a thick fluid forms. If needed, more water/cornstarch can be added until you have a thick fluid.

3. While over the newspapers, pour some of the cornstarch fluid into your hand. Tilt your hand slightly and record your observations on how the cornstarch behaves below.

4. While holding your hand over the cup, squeeze the fluid cornstarch. Record your observations below.

5. Place your fluid cornstarch back into the plastic cup.

6. Half-fill the bowl with crushed ice. Place the plastic cup into the ice. Leave it there for 5 minutes until the cornstarch has reached a colder temperature.

7. Pour some of the fluid cornstarch into your hand. Tilt your hand slightly and record your observations on how the cornstarch behaves below.

8. While holding your hand over the cup, squeeze the cooled fluid cornstarch. Record your observations below.

9. Place your fluid cornstarch back into the plastic cup.

10. Empty the crushed ice from the bowl. Half-fill the bowl with hot water. Place the plastic cup into the hot water and allow it to sit for 5 minutes.

11. Pour some of the fluid cornstarch into your hand. Tilt your hand slightly and record your observations on how the cornstarch behaves below.

12. While holding your hand over the cup, squeeze the warmed fluid cornstarch. Record your observations below.

13. Place your fluid cornstarch back into the plastic cup.

Conclusions: Answer in complete sentences.

Make a general statement relating the properties of fluid cornstarch to temperature and pressure (when you squeezed your hand). Does this match what you’ve learned about the motion of particles at different temperatures? Explain.

A non-Newtonian fluid is a fluid whose viscosity is variable depending on applied stress. A non-Newtonian fluid is one in which the shear stress and shear rate are linear, with the constant of proportionality being the coefficient of viscosity. At room temperature cornstarch fluid is thick and gooey. But, if we heat it up, it becomes thin and flows easily. Newtonian fluids behave like cornstarch fluid. Their viscosities (the resistance of a liquid to flow) are directly related to temperature, the higher the temperature the lower the viscosity and vice versa. A non-Newtonian fluid’s viscosity is also determined by the forces that act upon it. The viscosity also is correlated with how the force is applied.

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