Practice of Science PDF

## Practice of Science ### Pattern Seeking - Fair test - Classifying ### MAPDP - Change - independent - Marine - dependent - Same - controlled ### Let's Begin - Tom wants to buy some dry cells. - Both brand A and brand B claim that their dry cells have a longer life. - Question: Which one has a...

## Practice of Science ### Pattern Seeking - Fair test - Classifying ### MAPDP - Change - independent - Marine - dependent - Same - controlled ### Let's Begin - Tom wants to buy some dry cells. - Both brand A and brand B claim that their dry cells have a longer life. - Question: Which one has a longer life? - Tom decides to do a test to find out which brand of dry cells has a longer life. ### Basic Steps of a Scientific Investigation - Scientists find something that they do not understand. - They frequently ask questions and do scientific investigations. - A scientific investigation is a way to look for answers to questions. - It typically consists of five basic steps: 1. **Making Observations:** Scientists look carefully at the things they are interested in. 2. **Asking a question:** Scientists ask questions about their observations. 3. **Proposing a hypothesis:** Scientists suggest an idea to answer the question. This idea is called a hypothesis. 4. **Doing experiments:** Scientists typically conduct experiments to test the hypothesis. 5. **Drawing a conclusion:** Scientists determine if the results support the hypothesis. Then they draw a conclusion. - If the results do not support the hypothesis, scientists may revise the hypothesis and do experiments to study it again. ### The Discovery of Penicillin - Alexander Fleming was a doctor in the 1920s. - He conducted a scientific investigation that led to the discovery of a bacteria-killing substance (later called penicillin). - Penicillin is widely used to treat diseases caused by bacteria. - Fleming's investigation can be explained in five basic steps: 1. **One day, Fleming observed some mould on a dish of bacteria.** 2. **Fleming asked himself a question:** Why is there no bacteria growing around the mould? 3. **Fleming suggested an answer to his question:** The mould produces a substance that can kill bacteria. 4. **Fleming did experiments to test his idea:** Bacteria do not grow when the substance from the mould is present. 5. **Fleming found the results supported his idea. He drew a conclusion:** The mould produces a substance that kills bacteria. ### A Closer Look at the Basic Steps of Scientific Investigations - Scientific investigations can be explained using an example from everyday life. - Amy goes to a water park and wants to play on the slide. - She notices that people seem to move faster when the slope of the slide is steeper. - This is her **observation**. - Amy wants to conduct an investigation based on this observation. - Amy's question is: Does an object on a slide move more easily when the slope of the slide is steeper? - This question is not specific enough, as it doesn't state clearly what to measure. - **Amy modifies her question:** Does an object on a slide with a steeper slope take a shorter time to reach the ground? - This question clearly specifies what to measure: the time it takes for an object to reach the ground. - **Amy proposes a hypothesis:** An object on a slide with a steeper slope takes a shorter time to reach the ground. - **Amy designs an experiment to test her hypothesis:** She asks her teacher for advice and ensures the experiment is a fair test. - **Amy carries out the experiment and gathers data:** She compares the time it takes for different balls to reach the ground. - **Amy draws a conclusion:** An object on a slide with a steeper slope takes a shorter time to reach the ground. ### Variables - There are many variables that may affect the result of an experiment. - In Amy's experiment, the variables include the size of the ball, the mass of the ball, the material of the slide, the slope of the slide, etc. - **A fair test:** only changes one variable at a time. - **An independent variable:** is the variable that is changed. - **A dependent variable:** is the variable that is measured. - **Controlled variables:** are the variables that are kept the same. ### Identifying Variables - In designing a fair test, it is very important to identify all the variables. - There are three kinds of variables: - **Independent variable:** The variable that is changed. - **Dependent variable:** The variable that is measured. - **Controlled variables:** The variables that are kept the same. ### Example - Tom carries out an experiment to find out which brand of dry cells has a longer life: - He uses dry cells of brand A to power a torch and measures the time the torch lasts. - He then repeats the steps using dry cells of brand B. - **What variable should I change?** The brand of dry cells (Independent variable) - **What variable should I measure?** The time that the torch lasts for (Dependent variable) - **What variables should I keep the same?** The type of torch, whether the dry cells are new, etc. (controlled variables) ### Types of Scientific Investigations - Fair testing is not the only type of investigation. - Other types include: - **Pattern seeking:** Uses a large dataset to determine a relationship between variables. - **Classifying:** Groups similar things together to find a relationship or pattern. ### Go Further: Identifying Patterns from Graphs - **A graph can be used to show a relationship between two variables. For example:** - **A linear relationship:** As one variable increases, the other increases. - **A negative linear relationship:** As one variable increases, the other decreases. - **No relationship:** There is no clear connection between the variables. ### Classifying - In a library, books are grouped according to their subjects. - This allows users to find a certain book more easily. - Grouping similar things together is called classifying. ### Key Point - When scientists carry out investigations, they may also classify items according to their characteristics. - Scientists typically classify living things into animals, plants, etc. - Each group is further classified into smaller groups. - This helps scientists to study large numbers of living things in an organized way and identify unknown living things. ### Section Summary - **The Five Basic Steps of a Scientific Investigation:** Making observations, Asking a question, Proposing a hypothesis, Doing Experiments, Drawing a conclusion. - **Variables in a Fair Test:** Independent variable, Dependent variable, Controlled variables. - **Types of Scientific Investigations:** Fair testing, pattern seeking, classifying are examples.