Diffusion LN 7 Stinkbombs Why does the smell

Diffusion LN #7

Stinkbombs • Why does the smell of a stinkbomb travel? • Why does the smell eventually disappear? • Why do smells linger longer in a small room than in a large room?

Diffusion • Molecules move from an area where there are many to an area where there are few. – This is called moving down a concentration gradient. • Molecules move until they are evenly distributed. – Even distribution is called equilibrium. • Molecules can diffuse in a liquid or in a gas.

Solutions • A solution is a mixture of two or more substances. • Solute: a substance (like salt) that breaks up in a solvent (like water). • Solvent: a liquid with the power to break apart (dissolve) substances.

Solute size • If there are no barriers, a solute of any size eventually reaches equilibrium (or even distribution) in the solvent. • Cell membranes let small solutes in and out through diffusion. • Larger solutes (or molecules) can’t diffuse into the cell, and enter through special proteins or vesicles.

Osmosis • Osmosis is a kind of diffusion that refers to the movement of water. • Water likes to move from an area where there are few solutes to an area of many solutes. • In other words, water likes to dilute things. • Water molecules pass easily through membranes.

Osmosis words • HYPERTONIC – a solution has more solutes, or is more concentrated than another. • HYPOTONIC – a solution has fewer solutes, or is more dilute than another. • ISOTONIC – a solution has equal concentration to another.

Smelly Balloons § Like the plasma membrane, the balloon is a SEMIPERMEABLE MEMBRANE. § Semipermeable means that the membrane allows movement of certain molecules across. § Molecules small enough to fit through the pores in the balloon will move by DIFFUSION § Both in and out of the balloon. § The food extract smell molecules are small enough to diffuse through the membrane. § Eventually, the diffusing molecules reach the smell receptors in your nose.

Smelly Balloons • Each group will get 2 balloons initially • Fill in balloon number, scent, and strength of scent (none, weak, strong) in chart for all 7 balloons

• How do the smell molecules get out of the balloon? • This process by which molecules move from a place of higher concentration (inside the balloon) to a place of lower concentration (outside the balloon) is called • Tell two ways the latex skin of a balloon is like a cell membrane. • 1. • 2.

Summary 1. 2. 3. 4. 5. 6. What is diffusion? How do molecules move? What is solute? What is a solvent? What is osmosis? What are the different ways to describe a solution?