7th Grade Science Final Exam Review Packet-2014-2015

[Pages:34]Seventh Grade Science Final Exam Review Packet

Measurement and Tools of Observation

- Measurement: - Length: a measure of how long an object is end-to-end

- The base metric unit for length is the meter (m). In 7th grade, we most typically used the centimeter (cm, 1/100 of a meter) to measure length. - The tool used to measure length is a ruler.

- Temperature: a measure of the heat energy an object or substance has. - The base metric units for temperature are degrees Celsius (?C). - The tool used to measure temperature is a thermometer.

- Mass: a measure of the total amount of matter in an object or substance. - The base metric unit for mass is the gram (g). - The tool used to measure mass is a triple beam balance. - Weight: a measure of the force of gravity on an object - Weight is determined by multiplying the mass of an object by the force of gravity. - Weight changes with gravity; mass does not. For example, you would weigh less on the moon than you do on Earth due to the weaker force of gravity. However, on the moon, your mass would be the same as it was on Earth.

- Volume: a measure of the amount of space an object or substance takes up. In other words, it's how big an object or substance is.

- The base metric unit for solid volume is the cubic centimeter (cm3). The base metric unit for liquid length is the liter. In 7th grade, we most typically used the milliliter (mL, 1/1000 of a liter) to measure liquid volume. - The tool used to measure liquid volume is a graduated cylinder. - To measure the solid volume of a rectangular prism, the formula used is as follows: Volume of a rectangular prism = length x width x height

- To find the volume of an irregularly (strangely) shaped object, like a rock, the water displacement method is used.

- First, pour enough water into the graduated cylinder so that the water can cover your object, but not so much that it will go higher than the numbers on the graduated cylinder when you drop your object(s) in. Make note of the starting volume.

- Second, gently drop the object(s) into the water and measure the combined volume of the water and the object(s). Record this volume.

- Finally, subtract the starting volume of the water from the combined volume of the water and the object(s). The difference is equal to the volume of the object(s). The unit for solid volume is cm3. However, 1 mL = 1 cm3, so you do not have to change the number of your measurement, just the unit.

- Density: a measure of the mass of an object in a specific volume of that object. IN OTHER WORDS: It's how tightly packed the particles are of an object or substance.

- The formula for density is: Density = mass ? volume or D = m / V

- In 7th grade, we most typically used the units g/cm3 and g/mL

- Changing the volume of an object does not change its density. This is because when you change the volume, you automatically change the mass. For example, 60 cm3 of iron has a mass of 474.0 g. Using the formula for density we would find that 474.0 g ? 60 cm3 = 7.9 g/cm3.

Iron block: Volume = 60 cm3; Mass = 474.0 g; Density = 7.9 g/cm3

If we cut the iron in half so that we now only have 30 cm3, then the mass would also be reduced to 237.0 g. Again, using the formula for density, 237.0 g ? 30 cm3 = 7.9 g/cm3.

Iron block (cut in half): Volume = 30 cm3; Mass = 237.0 g; Density = 7.9 g/cm3

- Density and whether an object floats:

- If an object or substance has a density which is less than the density of a liquid, the object or substance will float in that liquid.

- For example: A wood block has a density of 0.7 g/cm3. Water has a density of 1.0 g/cm3. Since the density of the wood is less than the density of water, the wood would float in the water.

- If an object or substance has a density which is greater than the density of a liquid, the object or substance will sink in the liquid.

- For example: A piece of copper has a density of 8.9 g/cm3. Water has a density of 1.0 g/cm3. Since the density of copper is greater than the density of water, the copper would sink in the water.

Scientific Method and Experimental Design - Scientific method:

- The scientific method consists of 6 basic steps:

1) Make observations (quantitative and/or qualitative).

2) Based on observations, recognize a problem or form a question. Conduct background research about your problem or question.

3) Identify variables and construct a hypothesis (It's a possible answer to your question or solution to your problem.).

4) Design an experiment and test the hypothesis.

5) Analyze your results.

6) Draw conclusions (Was your hypothesis correct? Do you need to revise your original hypothesis? Is further testing needed?).

- Observations:

- There are two types of observations: quantitative and qualitative.

- QuaNtitative observation: an observation about the Number or amount of something.

- Examples of quantitative observations: Crystal is 113 centimeters tall. The mass of the rock is 873 grams. The volume of the pool is 2,000,000 liters.

- A qualitative observation is an observation made using your five senses, but is not made using numbers.

- Examples of qualitative observations. I can see the flowers from the tree are yellow. The sandpaper feels rough. The rock smells like rotten eggs. The liquid tastes sour. The smaller tuning-fork produced a high-pitched sound.

- When you make a qualitative observation, you are using your five senses. A good way to remember this is that a quaLitative observation is about what something Looks like. But remember, a qualitative observation can also be what something sounds, feels, tastes or smells like.

- Inference vs. observation - An inference is something that you think you know based on observations and prior knowledge. It is a conclusion based on observation.

- Examples of observations based on the above picture. All of the following sentences are factual.

- She has curly hair. - She has a choice of eating candy or fruit. - She is eating candy instead of fruit. - She is wearing a tank top. - She has brown hair. - Her eyes are closed. - Examples of inferences based on the above picture. The following sentences are not necessarily factual. They are just things someone might think based on observations. - Everyone prefers to eat candy instead of fruit. - She is hungry.

- Identifying a problem or asking a question - Based on the observations from previous page, there are many questions a scientist could ask. - For example: Do people with brown hair like candy? Do people usually eat with their eyes closed? Etc. - The question we will focus on is: Do people prefer to eat candy instead of fruit?

- Identifying variables

- Next, variables must be identified.

- Variable: something that might change (in an experiment). There are three types of variables, independent, dependent, and controlled.

- Independent Variable: a variable in an experiment which is intentionally changed or manipulated by the person conducting the experiment to affect the dependent variable. (It's the variable I control).

- If we were to make an experiment regarding our question about candy and fruit, an independent variable could be the choice of food being presented to people. The person designing this experiment would be in complete control of giving people the choice of eating fruit or candy.

- Dependent Variable: a variable in an experiment which is measured or studied. The person conducting the experiment cannot precisely control the dependent variable.

- If we were to make an experiment regarding our question about candy and fruit, the dependent variable could be what food people choose to eat. The person designing this experiment would not be in control of what choice people make.

- Controlled variables: variables which are kept constant (they do not change)

- If we were to make an experiment regarding our question about candy and fruit, controlled variables would be things like making sure each person has the same type of candy and the same type of fruit to choose between; making sure that each person is tested at the same time of day; making sure that the food is presented in the same way to each person.

- Writing hypotheses

- Hypothesis (plural: hypotheses): a suggested explanation for an observation

- Hypotheses are written using the independent and dependent variables.

- Hypotheses are always worded "If..., then..." - Generally, the independent variable is placed first in a hypothesis and the dependent variable is placed second.

- For example: If a person is given a choice between eating candy or fruit, then they will choose to eat candy.

- The first part of the sentence is the independent variable. The second part of the sentence is an inference or prediction which refers to the dependent variable. - Further investigation and/or experimentation can either support or oppose (not support) the hypothesis.

- Design the experiment

- Using your hypothesis as a framework, design an experiment which will either support or oppose your hypothesis.

- Based on the hypothesis we wrote above, "If a person is given a choice between eating candy or fruit, then they will choose to eat candy," a scientist might consider gathering a group of people (let's say 10 people) and giving each person a choice of candy or fruit to eat.

- The scientist will keep track of which choice the people in the experiment made.

- Record results:

- A data table should be used to record information obtained during the experiment.

- In the experiment from the last page, a data table would look something like this:

Person 1 2 3 4 5 6 7 8 9 10

Candy X X X

X

X

X X

Fruit

X X X

- Analyze results

- Turn the data gathered into factual statements.

- Based on the data table above, analysis might read like this: When testing 10 subjects to determine if a person would choose to eat candy if given the choice between candy and fruit, it was found that 7 people chose candy and 3 people chose fruit. Each subject was given the same type of candy and the same type of fruit and was tested at the same time of day.

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