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Phases and Temps
| Question | Answer |
|---|---|
| What is a measurement of particle motion called? | Temperature |
| The Farenheit scale originally based 0°F on what? | The coldest winter temperature in Germany |
| The Farenheit scale originally based 100°F on what? | Human body temperature |
| What is the coldest temperature possible called? | Absolute zero |
| What happens to particle motion at Absolute zero? | Particles stop moving completely |
| Which temperature scale was based on Absolute zero? | Kelvin |
| Name the melting point of ice in F C and K | 32F, 0C, 273K |
| Name the boiling point of water in F C and K | 212F, 100C, 373K |
| Name the freezing point of water in F C and K | 32F, 0C, 273K |
| Name room temperature in F C and K | 70F, 20C, 293K |
| Name human body temperature in F C and K | 98.6F, 37C, 310K |
| If you heat a block of ice over a stove from -20°C to boiling, what will the temperature graph look like? | Gradual increase from -20°C to 0°C, then it levels off for a while till all the ice has melted. Then gradual increase from 0 to 100°C and it levels off again at 100°C. |
| What happens when you put a test tube of boiling wax into cold water? | The tube shatters, the wax shoots up in the air and then ignites. |
| Why does boiling wax ignite when put in cold water? | Glass shatters when it quickly changes from hot to cold. This pushes the boiling wax up the tube and creates a lot of wax vapor. The wax vapor automatically ignites above boiling temperatures. |
| What is the melting point of paraffin wax? | About 50-6°C |
| Why does paraffin wax seem to have different melting and freezing points? | Because it is a mixture of several types of wax molecules. Shorter ones melt and freeze at a lower temperature. Longer ones melt and freeze at a higher temperature. |
| What is the melting point of milk chocolate? | About 30°C |
| Why does chocolate that has solidified at room temperature feel creamier and less firm? | Because at room temperature mostly the smaller phase 2 crystals form. The larger, firm crystals only form at warmer temperatures around 27°C. |
| How could you melt chocolate and get firmer, crisper texture? | Melt it all the way, then slowly cool it to about 27°C. Then add little chunks of seed chocolate that is already firm. |
| What temperature does salt water freeze at? (assume 100g salt per Liter of water) | About -6°C |
| What temperature does salt water boil at? (assume 100g salt per Liter of water) | About 103°C |
| Why does saltwater have a different freezing point than normal water? | Because the + and - salt ions stick to water molecules and prevent ice crystals from forming. It has to get much colder to force them to freeze. |
| Why does saltwater have a different boiling point than normal water? | Because the + and - salt ions stick to water, preventing it from leaving the liquid as a gas. It has to get much hotter to force them to boil away. |
| Why did ice water get much colder after we added salt to it? | Because salt force the ice crystals to melt. Melting required them to absorb heat from around them, so they feel much colder as they remove any surrounding heat. |
| How can you prevent condensation from forming on your glasses or car windshield? | Rub a thin layer of dish soap on them. And blow hot dry air on the windshield with the defrost and a/c setting. |
| What is dry ice? | Frozen carbon dioxide. Gas turns solid at -78°C. |
| How does a refrigerator work? | The tubes inside contain a liquid that absorbs heat from food and boils into a gas. This gas moves out of the fridge and gets compressed and hot. It gives off its heat outside the fridge, cools down and goes back in to start the cycle again. |
| What happens to particles of a substance during condensation? | Gas turns to liquid. Particles give off heat, slow down, and get closer together. |
| What happens to the particles of a substance during sublimation? | Gas turns directly to a solid. The same term also means solid directly to a gas. Like when dry ice turns into CO2 gas. |
| Why does it take 10 minutes longer to cook mac n cheese in Denver compared to Maine? | Because Denver is the "mile high city". At high elevations there is less gas pressure so water boils at a lower temperature. Food needs to cook longer at lower temps. |
| On hot summer days, why do water droplets form on cold soda cans? | Because of condensation. Humidity in the air touches the cold can, loses energy, and turns into a liquid. |
| Boiling 1 liter of water takes about how much energy? | 540 Calories, which is roughly the energy in 2 sticks of dynamite. |
| What happens to the pressure of a gas if you increase temperature? Why? | Pressure increases because particles are moving faster and pushing on the sides of the container. This is also why basketballs get flat when cold. |
Created by:
buchwalder