Warmup Mon, Dec 5

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Warm-up Mon, Dec 5

• Grab a blue textbook and, with a partner, answer
  questions 1 3 on p. 493 ON BACK OF LAST WEEKS
  PINK SHEET.

• Answers
• Frying an egg, eating a cookie, operating a power
  mower,etc.
• 3) Both create new substances. An exothermic rxn
  uses original substances to release energy, while
  an endothermic rxn absorbs the energy.

2
Burning Walnuts and Pecans

• Nut ? Ashes Energy

3
calorie vs. Calorie

• calorie- How much energy is needed to raise the
  temp of 1 mL of water one degree Celsius.
• Calorie- same as Kilocalorie
• Kilocalorie- How much energy is needed to raise
  the temp of 1,000 mL of water one degree Celsius.
  
• 1 Kilocalorie 1 Calorie 1000 calories

4
Lab Measurement of Chemical Energy in Food

• Introduction
• A biologist can measure the amount of chemical
  energy in food by burning the food. Breaking down
  molecules transfers the amount of energy stored
  in the molecules to heat energy. The heat
  released from burning food can then be used to
  heat water. The change in temperature of the
  water enables biologists to compute the energy
  change. Because of some inefficiency in the
  apparatus that is used, some heat will be lost to
  the environment.
• In this investigation, you are to measure the
  amount of heat released when a nut is burned. You
  are to calculate the amount of heat released in
  calories per gram in each sample.

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Pre-Lab

• Define calorie
• Define energy
• Define matter
• What is heat?
• Identify two sources of energy
• What is an element?
• What is a molecule?

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• Question Read the introduction carefully! What
  question can we ask?
• How much energy is there in a nut?
• Hypothesis Write an If, then, because...
  statement that attempts to answer the question.
• Materials
• scale
• large cork
• 10 ml graduated cylinder
• matches
• ring stand
• pin
• test tube
• test tube clamp
• 100 ml water
• thermometer
• 2 walnuts
• 2 pecans
• Procedure Construct a flow chart by watching Mr.
  Birklid carry out the experiment.

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Results

• Graph Plot a bar graph to show the change in the
  temperature of water due to heat energy released
  by the nut during your 4 trials.
• Plot nut type on the x-axis (the manipulating
  variable) for your data and class data.
• Plot kilocalories/gram on the Y-axis (the
  responding variable). See your data table.

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Analysis

• Which trial released the most energy? Explain how
  you knew this.
• Looking at the class averages of
  kilocalories/gram, which kind of nut had more
  energy? The pecan or the walnut? How did you
  know?
• How does your data compare with the class data?
  What differences do you notice? Identify possible
  sources of error in the way you conducted your
  experiment.
• Given the number of kilocalories per gram of the
  sample, compare your data with the given data on
  Known Values. What differences do you notice?
  Identify possible errors in experimental
  procedures that could have led to bad data.
• Most people can live on 1600 kilocalories per
  day.
• How many grams of peanuts would you have to eat
  to obtain this many kilocalories?
• How many grams of sugar?
• What is the relationship of a calorie to the
  chemical energy stored in foods?

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Sources of Error

• Write down how these errors would affect your
  experiment.
• Distance between tube and flame.
• Igniting nut without moving tube out of the way.
• Water boils.
• 29 mL of water used instead of 30 mL.
• Validity measure not taken get new water after
  each trial.

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Analysis

• Which trial released the most energy? Explain how
  you knew this.
• Looking at the class averages of
  kilocalories/gram, which kind of nut had more
  energy? The pecan or the walnut? How did you
  know?
• How does your data compare with the class data?
  What differences do you notice? Identify possible
  sources of error in the way you conducted your
  experiment.
• Given the number of kilocalories per gram of the
  sample, compare your data with the given data on
  Known Values. What differences do you notice?
  Identify possible errors in experimental
  procedures that could have led to bad data.
• Most people can live on 1600 kilocalories per
  day.
• How many grams of peanuts would you have to eat
  to obtain this many kilocalories?
• How many grams of sugar?
• What is the relationship of a calorie to the
  chemical energy stored in foods?

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Errors due to procedure

• Include a step dealing with the heat going into
  the air.
• Put the nut in the bottom of a jar OR
• Put a jar over the lab setup (apparatus).
• Allow O2 to reach the flame
• Use a different material than burnable cork. OR
  Validity measure Make sure nut is far away from
  cork.

13
Analysis

• Which trial released the most energy? Explain how
  you knew this.
• Looking at the class averages of
  kilocalories/gram, which kind of nut had more
  energy? The pecan or the walnut? How did you
  know?
• How does your data compare with the class data?
  What differences do you notice? Identify possible
  sources of error in the way you conducted your
  experiment.
• Given the number of kilocalories per gram of the
  sample, compare your data with the given data on
  Known Values. What differences do you notice?
  Identify possible errors in experimental
  procedures that could have led to bad data.
• Most people can live on 1600 kilocalories per
  day.
• How many grams of peanuts would you have to eat
  to obtain this many kilocalories?
• How many grams of sugar?
• What is the relationship of a calorie to the
  chemical energy stored in foods?

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Homework

• Answer the questions (formulating
  generalizations) at the end of your lab sheet in
  your conclusion section.
• Double-check your conclusion section. Make sure
  all sources of error were accounted for.