Density (9-20)
Chemical and Physical Changes (1-8)
Elements, Compound, and Mixtures (21-28)
Solutions, Suspensions, and Colloids (29-32)
12. List the different units used to measure the volume, mass, and density of solids and liquids.
Volume (for solid and liquid): Solid = centimeters cubed (cm3) and Liquid = milliliters (mL) Mass: grams (g) or kilograms (kg) Density (for solid and liquid): Solid = grams per centimeter cubed (g/cm3) and Liquid = grams per milliliters (g/mL).
1.Explain the difference between chemical and physical changes.
Chemical changes are changes in which two substances combine to create a new substance with different properties. They cannot always be reversed but sometimes they can be reversed with another chemical change. Physical changes occur when two substances are combined and each retains the same properties as the elements that make it up.
21. Define each of the following terms: element, compound, and mixture.
Element: a pure substance that is composed of only one type of atom. It cannot be broken down into simpler substances. Compound: a pure substance that is composed of two or more elements that are chemically combined. They combine to make a new substance with different properties. Compounds can only be separated by chemical reactions. Mixture: a substance that is composed of two or more elements that are physically combined. Each element keeps its own identity and properties. Mixtures can be physically separated.
29. Explain solute, solvent, and solution.
A solution is a homogeneous mixture of a solvent and a solute. The solute is the substance that is dissolved and the solvent is the substance that the solute is dissolved into. For example in a solution of salt water the salt is the solute and the water is the solvent.
16. What happens when you place an object with a density of 2.5g/cm3 into water that has a density of 1.0g/mL? Explain why your answer would happen.
The object would sink because it has a higher density than the water.
13. List the different tools that can be used to measure each of the following: Volume of a irregular shaped solid Volume of a regular shaped solid Volume of a liquid Mass Weight
Volume of a irregular shaped solid: graduated cylinder and water Volume of a regular shaped solid: ruler Volume of a liquid: graduated cylinder, beaker, measuring cup/spoon Mass: triple beam balance Weight: scale
7. List four different evidences of a chemical change.
Change in color, odor, the release of energy or heat, light, sounds, and bubbling or fizzing.
24. Compounds can only be broke down by a chemical change. List two specific ways to break down compounds.
adding heat or electrolysis (separating by electrical shock)
31. Compare and contrast heterogeneous and homogenous mixtures.
Homogenous mixtures are the same throughout. You can take a sample from any part of the mixture and it will have the same composition. Heterogeneous mixtures are different throughout. They may have clumps or large concentrations of different elements throughout a sample. They are similar because they are both mixtures and are made of one or more substance that is physically combined.
7. List five physical changes. 8. List five chemical changes.
Physical: Melting, mixing, separating, crushing, tearing, solid to liquid, liquid to gas, evaporating, dissolving, heating (but not cooking/baking/burning), grinding, and sanding. Chemical: rotting, digesting, rusting, corrosion (from acid or water) burning, baking, cooking, and electrolysis (the separation of water by electric current).
15. Explain what happens when you put liquids (that don’t mix) of different densities into a graduated cylinder?
The liquids with the highest densities would sink to the bottom to form layers. The layer on the top would be the liquid with the lowest density.
3. List four physical properties of matter. 4. List four chemical properties of matter.
physical properties of matter: color, shape, size, state, melting point, freezing point, boiling point, malleability (the ability to bend), density, volume, mass, or solubility (the ability to dissolve) chemical properties of matter: flammability (the ability to burn), reactivity with oxygen or water, or reactivity with acid (including vinegar).
26. Elements join to form compounds in a specific ______________.
mass ratio
30. Define and give an example of a solution, suspension, and colloid mixture.
Solution: a mixture with the smallest particles. It appears to be a single substance and it cannot be separated with a filter. Examples are tap water, soft drinks, gasoline, and salt water. Suspension: a mixture with the largest particles. It needs to be constantly shaken or stirred to remain mixed because the particles are large and will settle to the bottom. It can be separated with a filter. Examples include snow globes and water mixed with dirt/sand. Colloid: a mixture with medium particles. The particles are evenly dispersed like in a solution but they are not heavy enough to settle. However, the particles a large enough to scatter light making a cloudy substance. Examples are mayonnaise, milk, Jell-O, lotion, and whipped cream.
22. Write a chemical formula that represents a compound and one that represents an element.
Element: only one capital letter! C, H, Cl, Mg4, F8. Compound: two or more capital letters! C6H12O6, H2O, CO2, H2O2.
10. How would you find the volume of a regularly shaped object? 11. How would you find the volume of an irregularly shaped object?
regular = Measure the sides and multiply length x width x height. irregular = Pour a set amount of water into a graduated cylinder. Place the object into the cylinder and measure the displacement of the water. Displacement is the amount that the water rises when the object is placed in the cylinder.
5. Changes of state are considered which type of change? Explain why.
Changes of state are physical changes because the substance still has the same chemical properties, just in a different form. Water is still water (H2O) when it is a liquid, solid (ice), or gas (water vapor).
27. How is a compound different from a mixture?
Mixtures DO NOT combine in a specific ratio, they are physically combined and can be separated, the elements in the mixture keep their physical properties, and they do not form a new substance.
32. Solubility is a substances ability to dissolve. List three things that can make a substance more soluble.
crushing it into smaller pieces, adding heat, stirring or shaking quickly
17. Jack has a rock. The rock has a mass of 6g and a volume of 3cm3. What is the density of the rock?
D = m/v so the density of the rock equals 6/3. Density = 2 g/cm3.
14. How can you find the density of an unknown liquid?
I would find the mass of a clean, dry graduated cylinder, pour some of the unknown liquid into the graduated cylinder, and note the volume. Then, I would find the mass of the graduated cylinder with the liquid in it. Next, I would subtract the mass of the empty graduated cylinder from the mass of the graduated cylinder with the liquid in it to find the mass of the liquid. Finally, I would divide the mass of the liquid by the volume of the liquid by the volume of the liquid to calculate the density.
2.Why are chemical properties harder to observe than physical properties?
Chemical properties change the substances identity or makeup.
25. Why are compounds considered to be a pure substance?
It is a pure substance because compounds are composed of only one type of particle and the particles are chemically combined. Also different samples of any compound have the same elements in the same proportion. For example water is always composed of 2 hydrogen molecules and 1 oxygen molecule.
28. List 2 ways that mixtures can be separated.
filtering, settling, and evaporation
19. Alicia has a watch. It has a mass of 4g and a density of 0.8g/cm3. What is the volume of the watch?
D = m/v so the volume of the watch is 0.8 = 4/v. What goes into 4, 0.8 times? Volume = 5 cm3.
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