Dissolving vs. phase change. What happens to the atoms and the substances?

Transcription

1 Dissolving vs. phase change What happens to the atoms and the substances?

2 Atoms and molecules are the building blocks of matter! What did you learn about them from your readings?

3 What happened in the Saltwater lab? Did it change physically or chemically? We just moved the same molecules around so it is a change. Ask your self, can we get the salt back in some way? Yes, we just evaporate the water. Phase change just speeds up the molecules so it is another change! So we have a mixture of two substances in solution, salt and water.

4 Reading on Molecules pages S Water, ice, & water vapor are the same substance because they are made of the same molecules. 2. Water, ice, & water vapor are different states of matter of the substance water (liquid water, solid ice, and gas vapor). 3. You get different phases of water by adding or removing energy to speed up or slow down the molecules 4. The tiniest pieces of water of are molecules. 5. The molecules are made of atoms. 6. The specific atoms that make up water are 2 hydrogen atoms and 1 oxygen atom. 7. Yes, all water molecules the same. 8. Water molecules are very small, even smaller than a cell. 9. The molecules don t just hang out. The molecules are always moving.

5 How big are molecules?

6 How big are molecules?

7 What happened in the Saltwater lab? Did the volume stay the same or change? Why? Did the mass stay the same or change? Let s graph it! There was mass change. Nothing was and nothing was so the mass did not change! We call this of. It s the same for physical changes and chemical reactions. Mass cannot be created or destroyed; it is conserved if you can capture all the particles. This part can be tricky!

8 What else did you learn from reading about molecules in other substances?

9 Substances are made of molecules (reading pg S15-17) 1. Phases of water are all the same substance. 2. Every substance has its own type of molecule that is specific to that substance. 3. Different substances (like salt, sugar, and alcohol) have different molecules. 4. All molecules do not look alike because they are made of different atoms, depending on the substance. 5. Yes, all matter has molecules. 6. Energy, in forms like light or heat or xrays, is an example of something that s not matter so energy is not made of molecules.

10 Let s make some molecules & atoms

11 What s the difference between pure substances and mixtures? (reading pages S19-20) 1. A pure substance is matter that has only one type of molecule. 2. A mixture is matter that is made up of different types of molecules like saltwater. 3. Mixtures are more common in nature. 4. You can t always tell if it s pure or a mixture just by using your senses. 5. Some examples of mixtures are air, saltwater, koolaid, muddy water, salad dressing, lava, spit, etc Some examples of pure substances are pure water, or pure elements like gold or silver if there are no impurities (and that s hard to find!) 6. Yes, both pure substances and mixtures exist in more than one phase of matter. You just have to add the right amount of energy top change the phase.

12 Now you try to construct some molecules and figure out the chemical formula for each molecule of a substance (States of Matter Workbook pages S91-92) What does H 2 O (water molecule) mean? What does C 6 H 12 O 6 (simple sugar molecule) mean?

13 A really good question on Friday! Is fire matter or energy? Matter is anything that has mass and occupies space. The flame itself is a mixture of gases (vaporized fuel, oxygen, carbon dioxide, carbon monoxide, water vapor, and many other things) and so is matter. The light produced by the flame is energy, not matter. The heat produced is also energy, not matter.

14 What happens when something dissolves? Water has special chemical properties that make it a good liquid solvent for many substances. Water molecules attack (dissolve) the atoms, ions, and molecules of the solute, like salt or sugar. In its attack, the water pulls apart the solid grains at the atomic level, in slightly different ways that depend on the solute. Since sugar and salt are colorless solutes, and molecules are very small, you don t see them once they break up. But the solid solute is still there mixed with the liquid solvent.