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Gases and Temperature Physical Science Guided Notes ➔ Charles’ Law: for a constant amount of gas at constant pressure, temperature of the gas and volume of the gas will be directly proportional. ◆ Directly proportional relationship: as one value increases, the other increases, and vice versa. ◆ If a gas gets hotter, its volume will tend to get bigger. ◆ If a gas gets cooler, its volume will tend to get smaller. ◆ If the volume of a gas expands, it’s temperature will go down. ◆ If the volume of a gas shrinks, it’s temperature will go up. ◆ Think of it kinetically: as particles have more energy, they will hit the walls of its container more often, and harder. ◆ Heated air spreads out to increase volume of the balloon. ➔ We can represent Charles’ Law with this equation: 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑉𝑉𝑉𝑉𝑉𝑉 = 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑉𝑉𝑉𝑉𝑉𝑉 ➔ T (both initial and final) must be not in degrees celsius, but in degrees kelvin (K). ◆ Named after William Thomson, 1st Baron Kelvin, call him Lord Kelvin. ◆ This temperature scale has zero degrees set at the coldest possible temperature, absolute zero. ◆ As particles get cooler and cooler, they have move less and less, and temperature gets lower and lower. ◆ Zero on the kelvin scale is where particles (theoretically) have no motion ◆ Calculating a kelvin value from a celsius value is easy! (Degrees kelvin are the same size as degrees celsius, you see) 𝑉 = °𝑉 − 273.15 Physical Science Guided Notes If a 15 cm3 balloon at 23 °C is heated to 50°C, what will it’s new volume be? Ti = Tf = Vi = Vf = If a 15 cm3 balloon at 23 °C is compressed to 10 cm3, what will it’s new temperature be? Vi = Vf = Ti = Tf = If a 0.5 L cylinder of gas is heat from 300 K to 430 K, what will be the new volume of the gas? (assume the cylinder expands easily) Vi = Vf = Ti = Tf = Physical Science Guided Notes For the graph above, what will be the new temperature of 1250 cm3 at 15 K if it is compressed to 1000 cm3?