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Graduated Cylinder Practice
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Research: Scientific Attitudes These are the traits that scientists and researchers practice to ensure reliable results and good research work: Curiosity – Desire to ask questions and seek answers. Drives exploration and discovery. Example: Wondering why leaves change color in autumn. Intellectual Honesty – Reporting observations and results truthfully, even if they don’t support your hypothesis. Open-Mindedness – Willingness to accept new ideas and consider other perspectives. Perseverance – Continuing research despite difficulties or failures. Objectivity – Avoiding bias; basing conclusions only on evidence and facts. Positive Attitude Towards Failure – Viewing mistakes as opportunities to learn and improve. Skepticism – Questioning results and not accepting claims without sufficient evidence. Observation and Inference Observation – Using the senses (or tools) to gather information. Qualitative Observation → Describes qualities (color, shape, texture). Quantitative Observation → Uses numbers or measurements (height, mass, temperature). Inference – Logical explanation or conclusion based on observations and prior knowledge. Example: Seeing smoke and inferring there is fire. 🔎 Science Process Skills These are steps used in scientific investigations: Observing – Using senses and instruments to gather data. Inferring – Making explanations based on observations. Predicting – Stating what you think will happen based on patterns or evidence. Communicating – Sharing results through words, graphs, charts, or reports. Classifying – Grouping objects or data according to similarities and differences. Ordering/Sequencing – Arranging objects or events in correct order (time, size, importance). Measuring – Using standard units and instruments to describe length, mass, volume, time, etc. 📏 Measurement and Measuring Instruments Measurement – The process of comparing an unknown quantity with a standard unit. Common Quantities and Instruments: Length/Distance – Ruler, Meter Stick, Vernier Caliper, Tape Measure. Mass – Balance (triple beam, electronic). Volume – Graduated Cylinder, Measuring Cup, Pipette, Burette. Temperature – Thermometer. Time – Stopwatch, Clock. Electric Current – Ammeter. Voltage – Voltmeter. Key Idea: Accurate measurement requires using the correct instrument and unit (SI Units).Chapter 2 SUMMARY Mass measures how much matter is in an object. Weight can change when moving from one place to another, but mass generally stays the same. Properties are used to describe an object. Mass, volume, and density are important properties of matter. Mass is measured using a balance.A common unit of mass is the gram. Volume of liquids is measured by using a graduated cylinder. When measuring the mass of liquids,first measure the mass of an empty beaker. Then pour the liquid into the beaker and measure the mass again.Subtract these two figures to find the mass of the liquid. The volume of regularly shaped objects can be found by using formulas. The volume of irregularly shaped objects is measured by using the displacement of water method. Density is a property of matter that tells how tightly the matter of a substance is packed into a given volume. Density can be used to identify substances. Liquids that are less dense than water will float on water. Liquids that are more dense will sink.A solution is composed of a solute dissolved in a solvent. In the sugar water described in Figure 5-1, the solute was sugar and the solvent was water, and the solute molecules diffused through the solvent. It is also possible for solvent molecules to diffuse. In the case of cells, the solutes are organic and inorganic compounds, and the solvent is water. The process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration is called osmosis (ahs-MOH-sis). Because water is moving from a higher to lower concentration, osmosis does not require cells to expend energy. Therefore, osmosis is the passive transport of water. Direction of Osmosis The net direction of osmosis depends on the relative concentra- tion of solutes on the two sides of the membrane. Examine Table 5-1. When the concentration of solute molecules outside the cell is lower than the concentration in the cytosol, the solution outside is hypotonic to the cytosol. In this situation, water diffuses into the cell until equilibrium is established. When the concentration of solute molecules outside the cell is higher than the concentration in the cytosol, the solution outside is hypertonic to the cytosol. In this situation, water diffuses out of the cell until equilibrium is established. Observing Diffusion Materials 600 mL beaker, 25 cm dialysis tubing, funnel, 15 mL starch solution (10 percent), 20 drops Lugol’s solution, 300 mL water, 100 mL graduated cylinder, 20 cm piece of string (2) Procedure 1. Put on your disposable gloves, lab apron, and safety goggles. 2. Pour 300 mL of water in the 600 mL beaker. 3. Add 20 drops of Lugol’s solution to the water. CAUTION: Lugol’s solution is a poison and eye and skin irritant. 4. Open the dialysis tubing, and tie one end tightly with a piece of string. 5. Using the funnel, pour 15 mL of 10 percent starch solution into the dialysis tubing. 6. Tie the other end of the dialysis tubing tightly with the second piece of string, forming a sealed bag around the starch solution. 7. Place the bag into the solution in the beaker, and observe the setup for a color change. Analysis What happened to the color in the bag? What happened to the color of the water around the bag? Explain your observations. Quick Lab www.scilinks.org Topic: Osmosis Keyword: HM61090 mb06se_homs01.qxd 11/27/07 8:52 AM Page 98 HOMEOSTASIS AND CELL TRANSPORT 99 When the concentrations of solutes outside and inside the cell are equal, the outside solution is said to be isotonic to the cytosol. Under these conditions, water diffuses into and out of the cell at equal rates, so there is no net movement of water. Notice that the prefixes hypo-, hyper-, and iso- refer to the relative solute concentrations of two solutions. Thus, if the solution outside the cell is hypotonic to the cytosol, then the cytosol must be hyper- tonic to that solution. Conversely, if the solution outside is hypertonic to the cytosol, then the cytosol must be hypotonic to the solution. Water tends to diffuse from hypo- tonic solutions to hypertonic solutions. How Cells Deal with Osmosis Cells that are exposed to an isotonic external environment usually have no difficulty keeping the movement of water across the cell membrane in balance. This is the case with the cells of ver- tebrate animals on land and of most other organ- isms living in the sea. In contrast, many cells function in a hypotonic environment. Such is the case for unicellular freshwater organisms. Water constantly diffuses into these organisms. Because they require a relatively lower concentration of water in the cytosol to function normally, unicel- lular organisms must rid themselves of the excess water that enters by osmosis. Some of them, such as the paramecia shown in Figure 5-2, do this with contractile vacuoles (kon-TRAK-til VAK-y ̄ ̄o ̄ ̄o-OL), which are organelles that remove water. Contractile vacuoles collect the excess water and then contract, pumping the water out of the cell. Unlike diffusion and osmosis, this pumping action is not a form of passive trans- port because it requires the cell to expend energy. Copyright © by Holt, Rinehart and Winston. All rights reserved. (a) (b) Vacuole filling with water Vacuole contracting TABLE 5-1 Direction of Osmosis Condition External solution is hypotonic to cytosol External solution is hypertonic to cytosol External solution is isotonic to cytosol Net movement of water into the cell out of the cell none H2O H2O H2O H2O H2O H2O The paramecia shown below live in fresh water, which is hypotonic to their cytosol. (a) Contractile vacuoles collect excess water that moves by osmosis into the cytosol. (b) The vacuoles then contract, returning the water to the outside of the cell. (LM 315) FIGURE 5-2 100 CHAPTER 5 (a) HYPOTONIC Cell walls (b) HYPERTONIC (a) ISOTONIC (b) HYPOTONIC (c) HYPERTONIC Other cells, including many of those in multicellular organisms, respond to hypotonic environments by pumping solutes out of the cytosol. This lowers the solute concentration in the cytosol, bring- ing it closer to the solute concentration in the environment. As a result, water molecules are less likely to diffuse into the cell. Most plant cells, like animal cells, live in a hypotonic environ- ment. In fact, the cells that make up plant roots may be surrounded by water. This water moves into plant cells by osmosis. These cells swell as they fill with water until the cell membrane is pressed against the inside of the cell wall, as Figure 5-3a shows. The cell wall is strong enough to resist the pressure exerted by the water inside the expanding cell. The pressure that water molecules exert against the cell wall is called turgor pressure (TER-GOR PRESH-er). In a hypertonic environment, water leaves the cells through osmosis. As shown in Figure 5-3b, the cells shrink away from the cell walls, and turgor pressure is lost. This condition is called plasmolysis (plaz-MAHL-uh-sis), and is the reason that plants wilt if they don’t receive enough water. Some cells cannot compensate for changes in the solute con-Graduated Cylinders & Triple Beam BalancesReading Graduated CylindersGraduate nurse program - MPHMGraduate CV Q+AThe Graduate Survival Guide