Science Literacy: Chemical Change

1Hundreds of years ago, early scientists began to systematically explore the way that different compounds behave when mixed together. They mixed many, many substances to see what would happen. They made observations of the properties of the starting compounds and what happened when the substances first touched one another. They ran tests on the mixtures to see if the chemical properties had changed. They took careful notes and shared them with other scientists.

2When many observations were put together, scientists noticed patterns which led to a set of rules on how to tell when a chemical change had happened. Here are the five rules early scientists developed.

• There is a production of light.

• There is a production of a precipitate.

• There is a production of a gas.

• There is a color change.

• There is a change in temperature.

Even though these rules are old, they are still used today to determine when a chemical change happens. Each of these relies on a property which can be directly seen or measured in an experiment. This is called empirical evidence.

3 Maria had several compounds in the lab. She wanted to find out if a new substance is formed when certain pairs of them are mixed, so she designed an experiment to investigate. Maria used the five rules to determine if a chemical change had occurred.

4 Maria developed a procedure which she used for each mixture. First, she measured equal amounts of each of the two compounds to be mixed and put one of them into a test tube. She examined them carefully and wrote what she observed in her notebook. Watching closely, she put the second compound into the test tube, swirling to mix the two substances together. She put the test tube into the rack, let it sit for one minute, and then recorded her observations.

5 Here are the mixtures Maria tested and the observations she made.

a) Two clear liquids began to glow with a yellow light after mixing.

b) Two clear liquids were mixed but did not look any different afterward.

c) A piece of metal was dropped into a clear liquid. Before long, small bubbles began to float to the surface.

d) A clear liquid was added to a dark blue liquid. The resulting mixture was dark blue.

e) A clear liquid was added to a pale yellow liquid, forming a white powder which settled on the bottom.

f) She poured a clear liquid onto a white powder. Immediately, it fizzed and foamed. After one minute, the bubbles were gone and only a clear liquid remained.

6After the tests were complete, Maria reviewed her observations and analyzed her results to see if a chemical change had occurred. Soon Maria knew which combinations had produced a new substance. Do you?

After reading the passage above, answer the following six questions:

  1. Identify the flaw in the way that Maria set up her experiment.
  2. She did not take pictures. C. She did not measure the temperature.
  3. She did not wait long enough. D. She did not mix the substances well enough.
  4. Which of these describes Maria making an observation?
  5. Maria measured the compounds. C. Maria let the test tube sit for one minute.
  6. Maria wrote her results in. D. Maria saw that bubbles formed on the metal in her

her lab notebook mixture

  1. What is the best summary of this passage?
  2. Early scientists studied the way substances behaved when they were combined. They developed rules to identify when a chemical change occurred. Maria used those rules to create an experimental procedure to test six mixtures.
  3. Maria was curious about how several compounds acted when mixed. She put them into test tubes and swirled them together. She could tell if a chemical change had occurred by watching for signs like bubbles or light.
  4. Maria mixed compounds together to test for chemical change. One mixture produced light, two mixtures had bubbles, two mixtures had changes of color, and one mixture did not change.
  5. You can tell if a chemical change has occurred because there will be a production of light, gas, or a precipitate, or there will be a change in color or temperature.
  6. Using Maria's results, determine how many mixtures produced a new substance.
  7. 3 C. 4
  8. 5 D. 6
  9. Which is the best definition of empirical in Paragraph 2?
  10. Can be seen or measuredC. From a currently used procedure
  11. Collected in an old, reliable methodD. Did a chemical change occur
  12. Maria made a mistake in the analysis of her results. Which of the following conclusions is incorrect?
  13. A chemical change occurred in mixture (1) because there was a production of light.
  14. A chemical change occurred in mixture (2) because there was a color change.
  15. A chemical change occurred in mixture (3) because there was a precipitate formed.
  16. A chemical change occurred in mixture (4) because there was a production of a gas.

Compounds:How many elements are in the following compounds?

NH3 ______SbF5 ______BaTiO3 ______FeLiO4P ______

Potential and Kinetic Energy

  1. At which point does the ball have the greatest kinetic energy?
  2. Just after it is released, Point A.
  3. At the top of the flight path, Point B.
  4. Coming back down, Point C.
  5. Just before it lands, Point D.
  6. At which point does the ball have the greatest potential energy?
  7. Just after it is released, Point A.
  8. At the top of the flight path, Point B.
  9. Coming back down, Point C.
  10. Just before it lands, Point D.
  1. At which position(s) would the pendulum on the below have the most kinetic energy?
  2. ______
  3. At which position(s) would the pendulum on the below have the most potential energy?
  4. ______
  1. Potential and kinetic energy are similar in that
  2. Are demonstrated when an object is at rest
  3. Depend on the height of an object above the ground
  4. Can be converted into the other form
  5. Will produce an increase in the mass of an object
  1. What can be changed in the picture below to make the marble have more potential energy?
  2. ______
  1. At which point on the roller coaster below would the cart have the most potential energy?
  2. ______
  3. At which point on the roller coaster below would the cart have the most kinetic energy?
  4. ______
  5. Put the points in order from greatest to least potential energy: ______

Simple Machines

1.Name one advantage and one disadvantage of a pulley and an inclined plane in the table below:

Pulley Inclined Plane

2.The diagram shows an investigation in a science classroom. Students pulled the same mass up an inclined plane propped up on five blocks, then six, seven, and eight blocks. Each time, they use a spring scale to measure the forces needed to pull the mass up the inclined plane. This investigation can show how which of the following affects the force needed to move an object up an inclined plane?

  1. the mass of the object
  2. the height of the inclined plane
  3. the length of the inclined plane
  4. the surface area of the object

3. If you needed to move furniture into a van, why would it be easier to use an inclined plane than to just lift the furniture into the van?

  1. The inclined plane decreases the force of gravity that needs to be overcome.
  2. The inclined plane decreases the amount of force needed to move the furniture.
  3. The inclined plane increases the amount of force needed to lift the furniture.
  4. The inclined plane decreases the weight of the furniture.

4. The diagram below shows a fixed pulley system. Afixed pulley does not change the amount of workneeded to lift the load, but it does change the ----

  1. Volume of the force c. Direction of the force
  2. Weight of the load d. Shape of the load

5. The diagram below shows a 50N load attached to amoveable pulley. What amount of force must act onthe left rope of the pulley in order to lift the load?

  1. More than 50N
  2. 50N
  3. 25N
  4. Less than 25N

TRUE or FALSE

_____6. Fixed pulleys change the direction of force but not the amount.

_____7. Moveable pulleys reduce the amount of force needed by half but you have to pull up on the pulley.

_____8. For all simple machines: the amount of work stays the same.