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Chemical Building Blocks

Chemical Building Blocks. Chapter 2 – Solids Liquids and Gases Section 1 – States of Matter. Vocabulary . Solid Crystalline solid Amorphous solid Liquid Fluid Surface tension Viscosity gas. States of Matter.

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Chemical Building Blocks

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  1. Chemical Building Blocks Chapter 2 – Solids Liquids and Gases Section 1 – States of Matter

  2. Vocabulary • Solid • Crystalline solid • Amorphous solid • Liquid • Fluid • Surface tension • Viscosity • gas

  3. States of Matter • Our world is full of substances that can be defined as being one of the three primary states of matter • Solids, liquids and gases • Solids, liquids or gases can be elements, compounds or mixtures. • Air is a mixture of gases, but is made from elemental gases. • To truly define a solid, liquid or gas, we must look at their properties.

  4. Solids • If I pick up a rock, and just move it around the room, will it change shape? • If I take it outside right now, will it change shape? • Will it become bigger if I put it in a bowl? • No. • A solid has a definite shape and a definite volume. • This means it will keep its shape and volume in any position and in any container.

  5. Particles in a solid • The particles in a solid are packed very close together. • Also, tightly fixed in one position. • The particles are NOT motionless, but because of the tight packing, they vibrate back and forth only a little bit. • All students in the hallway.

  6. Types of solids • If in the solid, the particles form a regular, repeating pattern, crystals form. • Solids that are made up of crystals are called crystalline solids. • Salt, sugar, snow are examples • Always will melt at a specific temperature • In amorphous solids, the particles are not arranged in a regular pattern. • Plastics, rubber, butter, and glass are examples. • Does not melt at a distinct temperature, instead, may become softer or change into a new substance when heated.

  7. Picture of a crystalline solid

  8. Liquids • Liquids have a definite volume, but no shape of its own. • This means if I have 100 mL of a liquid, and pour it into a new container, I will still have 100 mL, but it may be shaped differently.

  9. Particles in a liquid • Particles packed ALMOST as tightly as in a solid, but not as close. • Particles can move around each other freely. • Usually in contact, but allows motion to occur. • Since particles can move around freely, liquids can move around (flow). • A liquid is a fluid, which is a substance which can flow.

  10. Properties of Liquids • Surface tension is the result of an inward pull around the molecules of a liquid that keep them together. • Is why water forms droplets that bead up on a surface • Allows insects to “walk” on water. • Viscosity is a liquids resistance to flowing. • Viscous liquids don’t flow much at all • Low-viscosity liquids flow easy.

  11. Gases • Gases are fluids, like liquids. • How does breathing show that gases are fluids? • However, a gas has no set volume, or shape. • A gas will fill up whatever space it can. • Gas particles stay apart from each other, and move around a LOT. • Because they move around a lot, they fill up whatever space they can!

  12. Chemical Building Blocks 2.2 – Changes of State

  13. Melting Melting point Freezing Vaporization Evaporation Boiling Boiling Point Condensation Sublimation Vocabulary

  14. Physical State and Temperature • Remember, particles of a substance with higher temperature have higher thermal energy. • Thermal energy ALWAYS moves from warmer substance to cooler substance. • Particles of a liquid have more thermal energy than particles of the same substance in solid form. • As a gas, has even more thermal energy.

  15. Changes between solid & liquid • Change of state from solid to a liquid is called melting. • This involves an increase in thermal energy. • In most pure substances, melting occurs at a specific temperature called the melting point. • Melting point often used to identify a substance.

  16. What is Happening • Melting • Increased thermal energy • Particles move faster, more • Faster moving particles = higher temperature • Eventually, move enough to separate from each other enough to become a liquid • At the melting point, the particles of a solid substance are vibrating so fast they break free from their fixed positions.

  17. Freezing • When freezing, the reverse of melting occurs • Loses thermal energy • Particles slow down • Temperature decreases • At freezing temperature, the particles of the liquid are moving so slowly they begin to form regular patterns (i.e. solid!) • Melting and freezing temperature are the same thing!

  18. Changing Between Liquid and Gas • The change from liquid to gas is called vaporization. • Vaporization takes place when the particles in a liquid gain enough energy to form a gas. • There are two main types of vaporization • Evaporation • Boiling

  19. Evaporation • Evaporation is vaporization that takes place at the surface of a liquid. • Shrinking puddle is an example • Water in puddle gains energy. • The added energy allows SOME of the water molecules on the surface to escape into the air. • Or, evaporate.

  20. Boiling • Boiling occurs when a liquid changes to gas below the surface as well as at the surface. • You see the results as bubbles form. • The temperature at which a liquid boils is called its boiling point. • As you heat up the liquid • Thermal energy increases • Particles move faster • Temperature increases • At boiling point temperature, particles have enough energy to move away from each other enough to be a gas. • Also used to identify an unknown substance.

  21. Boiling Point and Air Pressure • Boiling point depends on the amount of air pressure. • The less air pressure, less energy is needed for the particles to escape into the air. • Less energy needed = lower boiling point. • In Denver, CO, water boils at 95°C, not 100°C like at sea level.

  22. Condensation • The opposite of vaporization • Condensation occurs when a substances changes from a gas to a liquid. • The particles in the gas must lose thermal energy for this to happen. • Water vapor is impossible to see. • When you see steam, really seeing the tiny droplets of water suspended in the air.

  23. Changes Between Solid and Gas • It happens! • Sublimation occurs when the surface particles of a substance gain enough energy to form a gas. • During sublimation, particles do NOT pass through the liquid state to form a gas.

  24. Chemical Building Blocks 2.3 – Gas Behavior

  25. Vocabulary • Pressure • Boyle’s Law • Charles’ Law

  26. Measuring Gases • Whenever we deal with something, like to be able to measure it in some way. • Making quantitative measurements • When we work with a gas, we want to know three things • Volume • Temperature • Pressure

  27. Volume of gasses • Already discussed volume in previous chapter • Because gas particles fill up any available space, volume of gas = volume of container.

  28. Temperature of gasses • Remember: Temperature is the measure of the average energy of particles moving in a substance. • Faster particles = higher temperature • At room temperature (20°C), the average gas particles moves at 500 meters per second (more than 2x cruising speed of jet airplane).

  29. Pressure • Pressure is a force (push) divided by area being pushed. • Or, Pressure = Force / Area • Difference between sharp and dull knife. Which would have more pressure? • With a gas, pressure is the force of its outward push divided by the area of the walls of the container. • Measured in units of pascals (Pa) or kilopascals (kPa) (1 kPa = 1000 Pa)

  30. The “firmness” of a gas-filled object comes from the pressure of the gas. • “Firmer” objects have higher pressure • Higher pressure is due to a greater concentration of particles inside the gas-filled object. • If a hole is punched in the container, particles will leave the higher-concentration area to go to the lower-concentration area.

  31. Pressure & Volume • Bag demonstration • As I push bag, what happens to volume? • What happens to firmness of the bag? • Boyle’s Law states that when the pressure of the gas at constant temperature is increased, the volume of the gas decreases. • What does this mean if the pressure is decreased? • Relates pressure to volume.

  32. Weather balloons • High altitude weather balloons float because of helium gas inside of them. • High altitude = low pressure • What would happen to the balloon if they filled it up all the way on the ground?

  33. Pressure and Temperature • Remember, the faster particles are moving means the higher the temperature is. • Faster moving = hitting walls of container more often. • Hitting walls of container more often = • Higher pressure • When the temperature of a gas at a constant volume is increased, the pressure also increases. • Truck-driver tires.

  34. Volume and Temperature • Charles’ Law brings these together. Higher volume = higher temperature (for a constant pressure).

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