Unit 9 Blog- Emma Sember

Unit 9 is a unit where we took everything that we have learned this year, and applied to it to one problem or situation. For example, we learned about gases earlier this year but they appear again in this unit. In fact, we had to look back on unit 2 so that we could refresh our memory on pressure and volume when dealing with gases. Some of the things that i found helpful to review was standard pressure and temperature. Also reviewing that as volume decreases pressure increases and we call that an inverse relationship. In Unit 9 we applied these skills and made charts in order to find the volume or pressure of gases. This was demonstrated on worksheet 1.

We were then able to apply this to a lab where we found the volume of a mole of gas at standard pressure and temperature. We used a piece of magnesium ribbon, stopper and copper wire. After out calculations we were able to determine the mass of the copper wire, the volume of the gas collected and the vapor pressure of the water. All this was done by using a VNTP chart and setting up ratios to find moles. (which we have done in previous units)



After refreshing ourselves and combining past knowledge to solve problems, we then learned a new formula, PV=NRT. This formula says that pressure times volumes equals the number of moles times the constant, times the temperature of the given substance. The constant is always the same number (.0821 with liters times atm all over moles times k) without this constant we would not be able to solve for a given value. This number makes that possible. pv=nrt is a very straight forward formula that allows us to solve for a either pressure, volume, moles, or temperature when given the other values.

We were then able to apply this a balloon lab that we did in class called "The Air Bag Challenge". in this lab we had to determine how much CO2 was needed in inflate a balloon. we first did this by balancing out the equation that was given to us. And then by solving for the amount of moles we needed, we were able to successfully inflate a balloon to the right pressure so that it wasn't flat and
didn't pop.

In this unit we also learned about the concept of molarity. Molarity is the concentration of a solution given in grams and moles of a solute per liter of solution. Therefore, molarity is moles over liters in relationship to on another. Molarity allows us to calculate grams and the volume of an element by setting up proportions.

We also Applied this to a Kool- aid lab where we were able to determine the right about of Kool-aid needed for the amount of water that we were given. This was proven when we taste tested multiple cups of Kool-aid and some were very watery and others were very sweet and sour. By using molarity, we were able to determine the proper amount of moles and grams of kool-aid needed to make the best cup of kool-aid.

Overall, unit 9 brought together all the concepts that we have been learning throughout the year. The ideas of pressure, volume and moles were all brought together so that we could better understand the relationship between them. We solved many problems using math and BCA charts. This unit really helped me put all the concepts that I've learned this year and apply it not, only in my math work but in lab. 

2nd Blog- Emma Sember

When dealing with pressure and volume the number of particles and temperature are kept constant. The relationship is inverse. Which means that when the volume increases, the pressure decreases. This was shown in our first lab that we did.

Boyle's law (sometimes referred to as the Boyle–Mariotte law, or Mariotte's law) is an experimental gas law which describes how the pressure of a gas tends to decrease as the volume of a gas increases. A modern statement of Boyle's law is:

The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system.

Boyle’s law is basically saying that if the amount of gas and the temperature is unchanged then when the volume increases, the pressure will decrease. Basically, when the volume of a gas shrinks, the gas particles have less space to move around so they hit the sides of the container more often. The more often the gas particles hit the side of the container, the higher the pressure. So as the volume decreases, the pressure increases. This graph below shows the relationship between volume and pressure.

In the second lab, we were dealing with pressure and the number of particles. In this lab the volume and temperature are kept constant. This was a direct relationship. As the pressure increases so does the number of particles. The amount of pressure relies on the amount of particles that are present in that given space. So if there are more particles, there is a greater pressure and if there less particles the volume is also less. This explains why pressure and number of particles is a direct relationship because if one goes up the other goes up and if one goes down the other goes down as well. The graph below shows what the direct realtionship looks like.

 

In the third lab we were dealing with pressure and temperature. When the speed of the gas particles increases, the gas particles hit the walls more often. The more frequently the gas aparticles hit the walls, the higher the pressure. So, as temperature increases, the pressure also increases. If the gas cools, the impacts are less frequent and the pressure goes down. The relationship is also direct because if the pressure decreases the temperature also decreases and when the pressure goes up the temperature will also go up. Therefore, these two variables are directly related. The graph below shows this relationship.

When you drink through a drinking straw, you are not just sucking the liquid up the straw. When you suck all you are doing is removing the air in the straw, which allows the atmospheric pressure to act on the surface of the liquid to push it up the straw. As you put the straw into your mouth, you close your lips around the straw which seals off the surroundings from the inside of your mouth. When you increase the volume inside your mouth th pressure goes down. It goes down so that the outside surroundings has a higher pressure than the pressure in your mouth. This process forces the drink up the straw and into your mouth.

A thermometer is a device that measure the temperature of things. The red colored line in the middle of the thermometer moves up and down depending on the temperature. The thermometer measures temperatures in Fahrenheit, Celsius and another scale called Kelvin. Fahrenheit is used mostly in the United States, and most of the rest of the world uses Celsius. Kelvin is used by scientists. When you look at a regular outside bulb thermometer, you'll see a thin red or silver line that grows longer when it is hotter. The line goes down in cold weather. This liquid is sometimes colored alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated and smaller when cooled. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold.

Overall summary:

When we say that something has pressure the particles of that substance are colliding with the inside wall of the container.  If something has a higher pressure it means that the particles are more compact and are moving faster.Therefore, colliding with the wall more often and at a faster rate. Temperature is how fast the particles are moving inside something. The faster the particles are moving, the hotter the substance will be. So if the particles are moving more slowly, it will be at a colder temperature. That is why friction helps get us warmer. When we rub our hands together, the particles start moving faster and ultimately start to make us warmer.The only time that particles are not moving is at zero degrees Kelvin. This shows that it has no kinetic energy. This is also known as absolute zero. When there is a smaller volume, there is going to be a greater pressure. Since there is still the same amount of particles, they now have less space to occupy so they are more compact. Causing a greater pressure in a smaller volume verses a greater volume.

Links:http://indianapublicmedia.org/amomentofscience/drinking-straws-work/

http://chemistry.bd.psu.edu/jircitano/gases.html

http://www.mikeblaber.org/oldwine/chm1045/notes/Gases/GasLaw/Gases03.htm

Metal Lab

                 Throughout the course of the last two weeks I have learned many skills that have helped me enhance my knowledge of science. To start, I learned how to accurately calculate density, mass and volume. I was also reminded that density equals mass divided by volume. Mass divided by volume compares the mass for every one unit of volume. Volume will generally equal some unit cubed because it is length times width times height. But volume can sometimes be in ML because 1 ML is equal to centimeters squared. Mass and density are both physical properties of matter. But mass changes depending on the amount of material present and density remains the same regardless of how much material.

            I also learned the importance of significant figures and estimated digits when doing calculations. There will always be one estimated digit in a number. All place holder are zeros but not all zeros are place holders. All digits greater than zero are significant.

            Knowing the difference between chemical and physical change is a very important part of what I learned the past two weeks.  Chemical change is any change that results in the formation of new chemical substances. Some examples include, change in color, energy, or a change in the state of matter. In example, liquid to gas. Physical change rearranges molecules but doesn't affect their internal structures.  Something that really helped me get a better understanding of this concept was the chemical and physical changes in matter lab we did in class. It helped me better understand how to distinguish a chemical from physical change.

            All of the concepts helped my lad partner and I accomplish the Metal lab efficiently. We were given two different types of metal in two different cups. One was labeled Cup A and the other Cup B. Our goal is to find the Density of each of the Metals. First we calculate the mass of some of each metal and then all of each of the metals. We calculated the mass using the electronic balance. Then we have to calculate the volume of each of the metals. Normally we would do length, times width, times height but in this case we will use the method of water displacement. We fill the gradulated cylinder to the thirty milliliter mark. And add the metal. We observe what marking the water hits now. We repeat this step for each of the metals for both all and some. Once we have our volume calculations we are able to calculate density. We do this by taking the mass of the metal divided by the volume. And then we have completed the calculations for density and are ready to graph. 

Links: http://www.ausetute.com.au/density.html

http://www.chem.sc.edu/faculty/Morgan/resources/sigfigs/index.html