## Chem to Go 5

1. We used distilled water and ethanol.
2. The density would be 8.63 g/mL.
3. The density would be 0.48 g/mL.
4. The mass would be 465.31 g.
5. The volume would be 83.26 mL.
6. a) No this does not seem like a scientifically reasonable plan. b) The mass of the gold statue would be 0.0193 g. c) The statue would weigh 102.2 lbs. d) You would need 12.775 gallons of milk to be equivalent to the gold statue.
7. a) 1 kg lead b) 1 L gold c) 1 L silver
8. a) 1 kg feathers b) 1 kg water c) 1 kg copper

## Chem Talk #5

Today we measured the mass and volume of water and discovered a pattern with the densities we calculated. To calculate the density of water we took the mass of water and the volume of water and divided the mass by the volume. After that we also made a mass versus volume graph and found the slope. When measuring the mass we were measuring the amount of matter the object contains and when measuring the volume we were measuring how much space the object occupied. Every material has a mass and volume. If you wanted to compare two materials, in order to have a fair comparison of the “heaviness” of the two materials you would compare their densities. Density is the mass of the same volume of each material. When we were measuring we tried the best we could using the meniscus to get the most accurate and precise measurement. Our calculated densities were accurate and precise. I learned something new reading the Chem talk. I learned that accuracy and precision have different meanings. Accuracy refers to how close to the true value the series of measurements is whereas precision refers to how close a series of measurements are to each other. Tomorrow, we will investigate the relationship between density and flotation.

## Chem Talk #4

On Wednesday, we did an experiment where we made dough. The dough we made was an emulsion (side note: an emulsion is a colloidal dispersion of one liquid suspended in another.) After following the instructions to make the dough we split it into two samples and added strips of paper towel to only one of the pieces of dough and left the other piece untouched. When we added the paper towel to one of the pieces we made a composite (side note: a composite is a solid consisting of two or more substances.) Then we looked at the physical properties of the two pieces separately and compared them. We analyzed the texture, uniformity, strength, elasticity, bounce and malleability. Each physical property determines something about a material or in our case, the dough. The texture is how it feels and its appearance. Uniformity describes how consistent a material is throughout. Strength determines how well a material can withstand the application of a force. Elasticity determines how well the material returns to its original size or shape after a force has been applied. Bounce determines whether or not the object can return to its original position after it is dropped from a height. Lastly, malleability determines how easy it is to hammer the material into different shapes without it falling apart.

## Chem to Go #3

1. a) solution, colloid

b) suspension

c) colloid

d) colloid, suspension

e) solution

2. a) solutions: to separate a solution, the solvent needs to evaporate leaving the particles behind (evaporation)

b) colloids: cannot be separated, let the particles remain suspended

c) suspensions: to separate a suspension, you can filter the suspended particles (filtration)

3. Sugar: I think sugar represents a solution. Sugar is a pure substance and   if you added it to water the particles would dissolve completely and not be able to be seen by the naked eye. I think you would not be able to separate it through filtration because everything would pass through. Also I think the light beam will pass straight through the mixture making it a solution not a colloid. Sugar would be separated through filtration if it were a suspension.

Vegetable oil: I think vegetable oil represents a suspension. Based on the water and olive oil mixture I made before, I think vegetable oil would be similar. The particles will be large and visible to the naked eye and I think it will block the light beam completely making it a suspension. If vegetable oil were a solution you would not be able to see the particles with the naked eye.

Ketchup: I think ketchup represents a suspension. I feel like ketchup will have large particles and will block the light completely because it has somewhat same consistency of vegetable and olive oil. If ketchup were a colloid it would have the Tyndall effect where the light beam would be scattered but you can see where the light beam passes through the mixture.

White vinegar: I think white vinegar represents a solution. Vinegar is clear and transparent so when you mix it with water I think it will have dissolved particles you cannot see with the naked eye. Also I think you will not be able to separate it through filtration and that the light beam will pass straight through making it a solution. If white vinegar was a suspension the particles would separate during filtration.

No pulp orange juice: I think orange juice represents a solution. I think the   particles will be so tiny you cannot see them and I think the mixture will allow the light beam to go straight through. If orange juice were a suspension the particles would be seen especially if it had pulp.

## Chem Talk #3

In the experiment on Saturday, my group mixed different materials into six different test tubes with water and recorded our observations before and after. In the first test tube it was just water, in the second we added 0.6 grams of salt, in the third test tube we added 10 drops of coffee, in the fourth test tube we added 0.5 grams of Copper Sulphate, in the fifth test tube we added 2mL of olive oil and in the last test tube we added 0.5 grams of sand.

None of the materials we added to the water were pure substances. A pure substance contains only one kind of particle throughout such as sugar. Two or more pure substances combined is called a mixture and most things in nature are mixtures. In the second test tube when we added the salt to water we made a type of mixture called a solution. This mixture is called homogeneous because the particles that dissolve are so tiny you cannot see them with the naked eye. In this mixture the salt would be called the solute and the water would be called the solvent. The solute and solvent interact with each other to make the solution. The solvent is the substance that has the larger amount present.

In the third test tube when we added coffee to the water we made a type of mixture called a colloid. The drops of coffee did not settle out over time instead remained suspended in the water. In a colloid the dispersed particles are larger than those in a solution and you can see them through a microscope. When we tested the light beam through the colloid it was scattered but you could see the light beam passing through. This is known as the Tyndall effect.

The difference between a colloid and a suspension is that the particles in a suspension will settle out over time whereas in a colloid the particles will remain suspended indefinitely. When we added sand to the water we created a type of mixture called suspension. These mixtures have the largest of all the dispersed particles. The particles are visible to the naked eye. This mixture is heterogeneous, when we shone a light beam through the suspension it was scattered but it was not transparent unlike a colloid.

## Chem to Go 2

1.

 Evaporation Liquid Gas Gained Freezing Liquid Solid Lost Melting Solid Liquid Gained Deposition Gas Solid Lost Sublimation Solid Gas Gained Vaporization Liquid Gas Gained

2.

 Definite or Indefinite? Solid Liquid Gas Shape Yes No Yes Volume Yes Yes Yes

3.

4.

5. b) Copper is a solid at room temperature because 22 Celsius is very far away from 1083 Celsius (melting point) which is the only temperature it would start changing into liquid. Mercury is a liquid at room temperature because 22 Celsius is past its melting point (changed from solid to liquid) but the room temperature is lower than its boiling point (357 Celsius) which is only when it would change from a liquid to a gas. Oxygen is a gas at room temperature because 22 Celsius is above its melting and boiling points therefore it already went from a solid to a liquid and a liquid to a gas.

6.

7. The technique I would use is to heat the solution to a number in between their boiling points (78.5 and 100 Celsius) therefore the ethanol will vaporize but the water will still be a liquid.

8. The material it could be is sugar. Sugar as a solid is white and sugar is clear as a liquid. Its normal melting point is 146 Celsius.

## Chem Talk 2

In the experiment on Saturday, my group made qualitative observations using our sense of sight and focused on what was happening to the ice. We watched the ice change states, the ice melted to water and the water turned into vapor. We witnessed the three states of matter; solid, liquid and gas. When something changes states its physical properties change but not its chemical properties. Scientists believe there is a fourth state of matter; plasma (plasma is a high energy state of atoms and molecules).

When something touches our skin we immediately know whether it is hot or cold. It is not an accurate way to talk about temperature. To tell the temperature you can use a thermometer or the movement of the water drop can also give you some insight. The more energy the molecules have, the faster they move. As the air temperature increased the molecules moved faster inside the tube. Based on observations, scientists say that temperature is a measure of the average kinetic energy of the molecules of gas.

The normal melting point is the temperature at which a material changes from a solid state to a liquid state. The normal freezing point is the temperature at which a material changes from a liquid state to a  solid state. The normal boiling point is the temperature at which a material changes from a liquid state to a gaseous state. This is called vaporization, when a liquid changes to a gas. Although there is also sublimation which is when a solid changes straight into a gas.