Water’s In It?By

Carla Bridges

Indiana Standard

6.4.7 Explain that about two thirds of the mass of a cell is accounted for by water. Understand that water gives cells many of their properties.

Purpose

• You will be able to explain that about two-thirds of the mass of a cell is accounted for by water.

Materials

• Science Journal

• Pencil

• Watered Plant

• Paper Towels

• Scale

• Hair Dryer, heat vent, etc.

Pre-Activity Preparation

• Remove plant from soil and rinse off excess soil.

Pre-Activity Questions

• 1. What are all living things made up of?

• 2. What do you think cells are made up of?

• 3. How much water makes up a cell?

•

• 4.How much of an organism is made up of water?”

Pre-Activity Answers

• 1. Cells- All organisms are composed of cells

• The cell is the structural unit of life - units smaller than cells are not alive

• Cells arise by division of preexisting cells - spontaneous generation does not exist

• 2. Plasma membrane -separates the cell from the external environment

• Cytoplasm - fluid-filled cell interior

• Nuclear material - genetic information stored as DNA

Pre-Activity Answers Cont.

• Within cells there is an intricate network of organelles that all have unique functions. These organelles allow the cell to function properly.

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Pre-Activity Answers Cont.

• 3. A human cell is approximately 75% water.

• 4. An organism is made up of approximately 60%-90% water.

Activity

• When you water a plant, where does it go?• The water moves from the roots through the

internal structure to the cells of the plant.• How could you use a scale to determine how

much water a plant had in it?• Weigh your plant to see how much it weighs and

record your findings.• Place your plant on a paper towel and dry it with

a hair dryer, or lay it by a heat vent, or in the sun.

Activity (cont)

• Let your plant dry until you can see a visual difference.

• The longer it dries the less water there will be.

• Weigh your plant again and record your findings.

• Note the difference in the weights

• Subtract the dry mass from the wet mass: that is how much water was in your plant.

Post-Activity

• Approximately how much of the plant’s mass was water?

• Approximately how much of the cell’s mass was water?

Extensions

• Research properties of water that make it such an important substance for life(stores heat efficiently, bonds with other substances).

• Make oversized models of cells with approximate area taken up by water.

Standard Links

▫ 6.4.5 Investigate and explain that all living things are composed of cells whose details are usually visible only through a microscope.

▫ Language Arts 6.2.1 Features of Informational and Technical Materials: Identify the structural features of popular media (newspapers, magazines, online information) and use the features to obtain information.

Resources

• http://www.indianastandardsresources.org/files/sci/sci_6_4_7.pdf

• http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm

• http://www.answerbag.com/q_view/1020005

• http://library.thinkquest.org/12413/structures.html