# Objective 1: Nature of Science 1. Safety, Hypotheses, Experiments 2. Equipment, Measurement 3. Charts and Graphs 4. Conclusions 5. Reading Advertisements.

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Objective 1: Nature of Science 1. Safety, Hypotheses, Experiments 2. Equipment, Measurement 3. Charts and Graphs 4. Conclusions 5. Reading Advertisements and Nutrition Labels

Safety TAKS Hints  Most safety rules are common sense!  If there is an answer in which you have to ask a teacher or report to your teacher, that is probably the right answer.  Look carefully at any diagrams before answering the questions.

Safety rules you might not remember…  For dilutions, pour acid into water and stir (A comes before W)  A fume hood is used when a reaction will produce toxic fumes  Use goggles with chemicals, glassware or when heating anything.

Safety rules you might not remember… When heating something:  Wear goggles  Tie back long hair and loose clothing  Only heat open containers  Point test tubes being heated away from people  Do not reach across the flame

A testable hypothesis

 A hypothesis is a tentative explanation of the observations.  A hypothesis must be testable to be valid.  A valid hypothesis will not include feelings, emotions or opinions  A hypothesis can be rejected or revised if the data from the experiment do not support it.

Are these hypotheses valid?  Yellow labs are the friendliest dogs.  Most cats are afraid of thunderstorms.  Sharks can smell fear.  Eating chocolate causes pimples.

An experiment will test a hypothesis

Variables  In an experiment, variables are things that can change. In any experiment there are many variables that could change.  The independent variable is the variable that you want to change or manipulate in order to test your hypothesis. There can only be one independent variable in a controlled experiment.  The dependent variable is the result that you will be looking for to support your hypothesis.  The controlled variables are the other things that could change your results, but you need to keep constant in order to have valid data. These are also called constants.

Observations: Suppose you are trying to grow daisies in pots on your windowsill. You plant the seeds and watch them sprout and begin to grow. However, they are not growing as tall as the daisies that you have seen in the stores and you want to find out how to make them grow taller. You know that stores sometimes give their plants Miracle Grow and you want to find out if that will make your daisies grow better.

Planning the Experiment  What would be a good hypothesis?  What would be the independent variable?  What would be the dependent variable?  What variables would have to be controlled?

Given 2 mL of Miracle Grow each day Given 5 mL of Miracle Grow each day Given 10 mL of Miracle Grow each day How could you determine the independent variable just from this picture?

But, what if all the daisies died? Conclusion: Miracle Grow kills Daisies.

Groups  Experiments usually have experimental groups and control groups.  The experimental groups are those that receive some kind of treatment or are subject to some kind of condition (the independent variable).  The control group doesn’t receive the condition or treatment and is used to compare. (Like using a placebo when testing new medicines).

Given 2 mL of Miracle Grow each day Given 5 mL of Miracle Grow each day Given 10 mL of Miracle Grow each day What would make our experiment better?

Given 2 mL of Miracle Grow each day Given 5 mL of Miracle Grow each day Given 10 mL of Miracle Grow each day We need a control group. (One that doesn’t receive treatment.) Given ?

Trials The more trials or samples that you use to test a hypothesis, the better your data is.

Given 2 mL of Miracle Grow each day Given 5 mL of Miracle Grow each day Given 10 mL of Miracle Grow each day How could we make this experiment better? Given no Miracle Grow

Quick TAKS tips about Experiments 1. Remember that there should only be one variable changed at a time. Discard any setups that change more than one variable. 2. The questions often describe an experiment that has already been setup and ask you to identify the question or the hypothesis. To solve these, first identify what the variable was that was tested (it will be the thing that is different for each experimental group.) 3. A control group will always improve an experiment. Look for a control group that is the most “natural setting” for the thing being tested. 4. More trials give better data. Data from a few trials (or just a few samples) might give you incorrect results. 5. Random sampling is better than taking samples in a pattern.

Scientific Tools

Balance – measures mass (g)

Measuring volume of liquids

X A beaker is not precise. A graduated cylinder is more precise. A pipet or a buret are the most precise.

What is the volume of Object X?

How do you fill this out? 42.5 425

Precise / Consistent  Precision in measuring means you can measure to the most numbers after the decimal point.  The tools with the most markings between numbers give the most precise measurements.  When given a list of measurements, the most precise or consistent measurements are those which are most similar to each other.

Quick TAKS tips about Measuring  When deciding what to use for measuring volume, make sure the container that you use is big enough to hold the liquid (You cannot put 100 mL of water in a 10-mL graduated cylinder).  Remember that a pipet or buret are the most precise for small amounts, followed by a graduated cylinder. The beaker is not precise.  Don’t forget that you have a ruler on your formula chart to use if needed.

Graphs  Bar Graphs  Line Graphs (scatter plot)  Circle Graphs (pie chart)

Bar Graphs  Represent discreet data sets

Line Graphs  displays continuous data  shows trends in data  You can make predictions

Line Graphs

Circle Graphs  Show parts of a whole

Half-Life  used to describe radioactive materials.  Half-life is a measurement of time.  To find half-life, find how long it takes for half of a substance to decay.

Half-Life

TAKS Tips for Reading Graphs and Charts  Look at the chart/graph first and circle important information.  Read the title  Read the labels on the x and y axis and the key if one is given.  Write on the graphs – make points, circle numbers, or extend lines when needed.  Use a straight edge when needed  Don’t be intimidated! Many times, all of the information needed is given in the graph.

Valid Conclusions  When you make a conclusion you are making a statement that describes the data collected in an experiment.  When you make an inference, you use logic and your own experience and knowledge to make a statement about your data. “Reading between the lines”

The graph below shows information about sleep habits of newborn babies, one-year-olds, four-year-olds, and ten-year-olds. Each solid bar represents a period of sleep.

Quick TAKS tips about Conclusions  Read all parts of the chart, graph or statement before answering.  For complex charts, read carefully, making notes as you go.  Try out each conclusion statement with the data and see if it fits the data given. Cross off the statements that are definitely not true.

Reading Advertisements and Nutrition Labels  Use all of the skills that you have developed and apply to real-world advertisements.  Almost always, all the information you need is given in the ad or label – you do not need to know anything about the product.  Good science still applies!