1. Pure substance: made up of only one type of atom or molecule
Mixture: two or more different elements chemically joined
Compound: two or more different elements not joined
Element: made up of only one type of atom
2. When salt is stirred into water, it dissolves. The salt is a solute, which mixes with the water to form a solution. Sugar would not dissolve in oil. The salt will dissolve in water because water molecules are polar and can surround and separate the ions in salt. When a solution cannot dissolve any more solute we say it is saturated.
3. To separate sugar from water, you can use evaporation. Heat the mixture gently in an evaporating dish. As the water heats up, it turns into steam and leaves the sugar behind as a solid residue. This works because sugar has a much higher boiling point than water and does not evaporate with it.
4. Correct definition of diffusion: movement of particles from an area of high concentration to an area of low concentration, until equilibrium.
5. (From left to right, top to bottom)
- Evaporation
- Filtration
- Decanting
- Distillation
6. Characteristics used to help identify a pure substance:
- Fixed melting and boiling points
- Constant composition throughout
- Cannot be separated by physical means
- Shows consistent chemical properties
7. True/False:
- [ ] You can describe dissolving → False
- [ ] You can easily separate mixtures of elements and compounds → False
- [x] You can describe diffusion → True
- [x] You can identify and classify substances → True
- [x] You know how to identify a pure substance → True
Parent Tip: Review the logic above to help your child master the concept of separation techniques worksheet.
