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ANSWER KEY
1. Explain the difference between physical and chemical changes.
Physical changes just change the way a substance looks, but the substance stays the
same. Chemical changes produce a new substance.
2. Identify the following changes as either physical or chemical.
A) burning wood chemical
B) baking brownies chemical
C) digesting food chemical
D) dissolving sugar in hot water physical
E) melting butter physical
F) exploding fireworks chemical
G) rusting iron chemical
3. Give an example of a mixture that is a solution and a mixture that is not a solution. Explain
your answer.
A mixture that is a solution is really well mixed and something is being dissolved in a
liquid. For example: Kool-Aid, coffee, lemonade, tea, hi-c, sugar water. An example
of a mixture that is not a solution is trail mix, salad, cereal, spaghetti and
meatballs.
4. Compare and contrast the properties of a homogeneous mixture, such as salt water, and a
heterogeneous mixture, such as muddy water.
A homogeneous mixture is well mixed. A heterogeneous mixture is not mixed well.
Both of these are mixtures.
5. Circle the following example that is a solution: cranberry juice, a bowl of cereal and milk,
chocolate chip cookie dough? Why is it a solution? It is really well mixed and something
is being dissolved in a liquid
6. Compare and contrast the changes a piece of paper undergoes when it is torn into tiny
pieces and when it is burned
When a piece of paper is torn it undergoes a physical change because it is still paper
and has the same characteristics. When a piece of paper is burned it is a chemical
change because it has turned into a new substance.
7. During the experiment with the liver and the potato, hydrogen peroxide was changed into
water and oxygen. Did you see anything during the experiment that showed oxygen was
given off? Explain.
Through observations during the lab you could see a continuous stream of bubbles.
Those bubbles were oxygen.
8. What are some indicators that chemical changes are taking place?
Odor, burning, new substance is formed, bubbles, color change, temperature change,
rusting, smoke, sound
9. Draw and label 3 pictures to represent the molecules in the three main states of matter.
SOLID
LIQUID
GAS
10. Calculate the density of an object that has a mass of 12.6 kg and a volume of 3 dm3.
Density = mass / volume
MEMORIZE!!!!!
12.6 / 3 = 4.2 kg/dm3
11. Calculate the mean, median, mode, and range for the following data set:
14.9, 13.9, 13.9, 12.8, 11.7, 15.2
Mean = 13.73 (add them all up and divide by 6)
Median =
11.7, 12.8, 13.9, 13.9, 14.9, 15.2
13.9 +13.9 / 2 = 13.9
(find the middle number; if there are 2 middle numbers find the average of the two)
Mode = 13.9 (the number that occurs most often)
Range = 15.2 – 11.7 = 3.5
(largest value – the smallest value)