X Chemistry Unit 1 Notes:



X Chemistry Unit 1 Notes:

Experimental Design & Lab Safety

What Is Chemistry?

← Biology –

← Physics –

← Chemistry –

The Scientific Method

A. Scientific method – the steps someone takes to identify a _______________, develop a _________________, design and carry out steps to __________________________________, and document observations and findings to share with someone else.

← It is a way to solve a problem

B. The Steps of the Scientific Method:

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C. Breaking Down the Scientific Method

← Scientists have to take the time to _________________________________ when they are investigating a question or a problem.

o They break things down into ________________________ that make sense.

← Scientists _____________________________________, gather information, and form a _____________________________.

← The next step scientists take is to create and ___________________________________ to test their hypothesis.

← A key to experiments is ______________________________________ and writing it down.

o Gathering information or data and documenting it so it is readable and makes sense to others is very important.

← Once a scientist completes an experiment, they often ______________ it to see if they get the same findings and results.

o This is called _______________________, or checking things out to make sure everything was valid and will happen again and again.

← Scientists share their experiments and findings with others.

o Because they share their experiments and findings, scientists can learn from each other and often use someone else’s experiences to help them with what they are studying or doing.

D. What Next?

← If they hypothesis is supported, then the experiment is ___________________________ ________________________________________________________________________

← If the hypothesis is not supported, then the hypothesis is _________________________ ________________________________________________________________________

E. Examples

The Strange Case of BeriBeri: In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was beriberi. Symptoms of the disease included weakness and loss of appetite, victims often died of heart failure. Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of patients with beriberi. The injected chickens became sick. However, so did a group of chickens that were not injected with bacteria.

One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this interesting case. He found that polished rice lacked thiamine, a vitamin necessary for good health.

1. State the Problem

2. What was the hypothesis?

3. How was the hypothesis tested?

4. Should the hypothesis be supported or rejected based on the experiment?

5. What should be the new hypothesis?

How Penicillin Was Discovered: In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that a mold called Penicillium was also growing in some of the dishes. A clear area existed around the mold because all the bacteria that had grown in this area had died. In the culture dishes without the mold, no clear areas were present.

Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided to isolate this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a nutrient broth solution. This solution contained all the materials the mold needed to grow. After the mold grew, he removed it from the nutruient broth. Fleming then added the nutrient broth in which the mold had grown to a culture of bacteria. He observed that the bacteria died.

6. Identify the problem.

7. What was Fleming's hypothesis?

8. How was the hypothesis tested?

9. Should the hypothesis be supported or rejected based on the experiment?

Put the following statements in order according to the scientific method and label each statement with the appropriate step of the scientific method.

o Jenny determines that her homemade solution was just as effective as the store-bought pesticides

______________________________________________________

o Jenny states that if she sprays her vegetables with a natural, homemade solution to help fight the bug problem, then her vegetables will still grow to the same size as they would if she used store bought pesticides

______________________________________________________

o Jenny goes to the library and looks up different kind of pesticides and their effect on vegetables and also looks up natural remedies to help solve her bug problem

______________________________________________________

o Jenny sprays one third of her vegetables with store bought pesticides, one third with her homemade solution, and does not spray the remaining third (her control group)

______________________________________________________

o Jenny wonders how she can protect her plants from bugs without harming the vegetables

______________________________________________________

o After one week, Jenny compares and tests the differences in her vegetables

______________________________________________________

Experimental Design

Every experiment has two parts: the ______________ group and the ____________________ group

A. Control Group – this set-up is the standard by which the test results can be compared

o This group contains the population where __________________________________

B. Experimental Group – _________ factor is changed between the control group and experimental group

o The changes found in this set-up are usually due to the _________________ (the factor that was changed)

C. Variable – something that can be ___________________ between the control group and the experimental group

o It is the goal of an experiment to determine the effect the variable has on what is being test

o There are usually two variables when an experiment is performed

▪ The __________________________ variable

▪ The __________________________ variable

D. Independent variable – the factor that, as it changes, _________________________________ __________________________________

o The experimenter sets the independent variable

E. Dependent variable – factor that changes as a result of changes in the ___________________ ___________________

o It ____________________ on the other variables!

F. Example:

A group of college students were given a short course in speed-reading. The instructor was curious if a monetary incentive would influence performance on a reading test taken at the end of the course. Half of the students were offered $15 for obtaining an A or B on the test; the other half were not offered money.

Independent variable:

Dependent variable:

Experimental group:

Control group:

Experimental Design Example

Let’s say I am from Mars and have never seen the leaves change color. I decide to perform an experiment to find out why they change color.

My Hypothesis: Since the leaves change color in the Fall and since it gets cold in the Fall, I believe that the leaves change color due to the drop in temperature.

Groups: I went to Waterloo Gardens intent on finding two identical maple trees. I found two that were about the same height, had about the same number of leaves, were in the same type of soil, and were in the same amount of soil.

When I went home, I placed one of the trees in a closet with a lamp that was on a timer so that the tree would receive 12 hours of light each day. I placed the other tree in a different closet that was the same size and that received the same amount of light (12 hours).

After some research, I found that the average summer time temperature was 85° and set a heater and a thermostat in one of the rooms to simulate summer time. I also found that the average temperature in the winter was 42° and set a cooler and a thermostat in the other room to simulate winter time.

While conducting the experiment, I gave each plant the same amount of water at the same time each day, applied the same amount of fertilizer on each tree, and kept a neat and detailed data log on each plant that kept track of the percentage of green leaves.

|Week 1 |Week 2 |Week 3 |Week 4 |Week 5 |Week 6 |Week 7 |Week 8 |Week 9 | |Cold tree |100% |98% |98% |97% |99% |97% |99% |95% |99% | |Warm tree |100% |99% |95% |97% |100% |98% |98% |93% |98% | |

****Conclusion: After analyzing the data, can you conclude that temperature was the cause of the leaves changing color in the fall?

• Identify the variables in the experiment:

– Which ones did I keep the same in each experiment?

– Which ones did I change in each experiment?

• Identify the independent variable?

• Identify the dependent variable?

• Identify the control set up (group)?

• Identify the experimental set up (group)?

Safety in the Laboratory

Please record the safety rules noted in class in the space provided. Feel free to use loose leaf if you need more room.

Safety in the Laboratory (cont.)

Please record the safety rules noted in class in the space provided. Feel free to use loose leaf if you need more room.

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