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Magnetic Attraction

Magnetic Attraction. After you have separated the sand and salt from the bigger materials using sifting – you can use a magnet to pick up the objects made out of certain metals such as paper clips and safety pins. Could you use a magnet to separate Sand, marbles, and plastic beads?

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Magnetic Attraction

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  1. Magnetic Attraction After you have separated the sand and salt from the bigger materials using sifting – you can use a magnet to pick up the objects made out of certain metals such as paper clips and safety pins. Could you use a magnet to separate Sand, marbles, and plastic beads? Why or why not?

  2. Floatation Floatation is using a liquid to separate materials of different densities. A material that is less dense will float on a material that is more dense. Plastic beads are less dense than marbles. How would you separate marbles from plastic beads using floatation?

  3. Filtration You can also separate solutions by filtering them. Filtration is separating solids from liquids by passing a mixture through a filter. Salt dissolves in water while sand does not. How could you separate salt and sand using water and a filter?

  4. Evaporation After you have filtered out the sand from the solution of salt water, you can use evaporation to separate the salt from the water. When water evaporates from the mixture, solid salt particles will be left behind. How would evaporation naturally separate dirt from water in a mud puddle?

  5. Chromatography Chromatography separates solutions by dissolving them in special liquids. For example, chromatography can be used to separate substances such as pigments in a leaf like in the picture. The police department uses chromatography to separate and identify all kinds of substances.

  6. How can we make a solution more or less concentrated? The concentration of the solution is a measure of the amount of solute compared to the amount of solvent. If the amount of solute is small compared to the amount of solvent, the solution is said to be dilute. If the amount of solute is large compared to the amount of solvent, the solution is said to be concentrated.

  7. Concentrations For example, if you took one gram of salt and added it to 100 grams of water, the solution is dilute. If the same amount of water has 30 grams of salt, the solution is concentrated.

  8. Rate of Dissolving You know that salt easily mixes with water by dissolving in it. But did you know that salt can dissolve at different rates? The temperature of the water, the size of the salt particles, and how you stir the solution are factors that affect how quickly the salt dissolves.

  9. Temperature Temperature affects the rate of dissolving in a solution. The particles of a substance are always moving. When heat is added, the particles move faster making it dissolve faster in a liquid. Think about adding sugar to ice tea vs. hot tea. Which one dissolves faster?

  10. Particle Size Another factor that affects the rate of dissolving is particle size. The smaller the solute particles are, the faster they dissolve. If you have ever made a cup of hot chocolate, you dissolved powder into milk. If you put a piece of a chocolate bar in the milk, it would take a longer time to dissolve.

  11. Stirring Stirring also affects the rate of dissolving. When adding particles to a liquid, you stir or shake the liquid. This action makes the solute dissolve more quickly. What happens if you pour a drink mix into a container without stirring?

  12. Solubility • Solubility 4:15

  13. Chemical ReactionsLet's start with the idea of a reaction. In chemistry, a reaction happens when two or more moleculesinteract and something happens. That's it. What molecules are they? How do they interact? What happens? Those are all the possibilities in reactions. The possibilities are infinite.

  14. A few key points: • A chemical change must occur. You start with one compound and turn it into another. That's an example of a chemical change. A steel garbage can rusting is a chemical reaction. That rusting happens because the iron (Fe) in the metal combines with oxygen (O2) in the atmosphere.

  15. When a refrigerator or air conditioner cools the air, there is no reaction. That change in temperature is a physical change. Nevertheless, a chemical reaction can happen inside of the air conditioner.

  16. Another chemical reaction:

  17. How is a chemical change different from a mixture? • A compound is a type of matter made of a combination of elements. In a compound, two or more elements are combined chemically. • Water is made up of two atoms of hydrogen and one atom of oxygen. H20

  18. The proportion of hydrogen and oxygen atoms in water is always the same. • If the proportion of elements in a compound is changed, a new compound is formed. • Both water and hydrogen peroxide are made of hydrogen and oxygen atoms. • However, a molecule of hydrogen peroxide contains two hydrogen atoms and two oxygen atoms. • Hydrogen peroxide is NOT like water and you should not drink it. H2O2

  19. Separating Compounds • When elements combine chemically, they from compounds with properties that are different from the properties of the individual elements. • These elements cannot be easily separated like in a mixture.

  20. Matter and its Properties • Full video 17:06 ( a good review or watch segment on chemical reactions 1:53)

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