Variables, Changes, and Properties

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Questions and Answers

In an experiment studying the effect of temperature on the rate of a reaction, what is the independent variable?

The independent variable is the temperature.

A student is conducting an experiment to see how different liquids affect plant growth. They use water, orange juice, and milk. What would be a suitable control variable for this experiment?

A suitable control variable would be the amount of liquid given to each plant and the type of plant.

Classify melting ice as a physical or chemical change and explain why.

Melting ice is a physical change because the substance (water) remains the same, only its state changes.

Explain why burning wood is considered a chemical change.

Burning wood is a chemical change because it produces new substances like ash and gases, and the process is irreversible. Signup and view all the answers

A student wants to investigate how the amount of sunlight affects the growth of bean plants. Formulate a suitable aim for this investigation.

To investigate the effects of the amount of sunlight on the growth of bean plants. Signup and view all the answers

A student believes that increased study time will improve test scores. Write a hypothesis for this.

If study time is increased, then test scores will improve, because more time spent studying leads to better understanding and retention of the material. Signup and view all the answers

Describe two key physical properties of metals.

Metals are malleable (bendy and soft) and are conductors of electricity. Signup and view all the answers

What are two distinguishing properties of non-metals?

Non-metals are dull (lack in lustre) and are insulators (unable to conduct heat or electricity). Signup and view all the answers

Explain how metalloids differ from both metals and non-metals.

Metalloids have properties of both metals and non-metals, and their properties can be modified. Signup and view all the answers

Where are metals, non-metals, and metalloids generally located on the periodic table?

Metals are on the left, non-metals are on the right, and metalloids are in the middle. Signup and view all the answers

Outline the key achievements of Dmitri Mendeleev in developing the periodic table.

Dmitri Mendeleev created the periodic table and grouped elements with similar properties, sorted by mass, and left gaps for undiscovered elements. Signup and view all the answers

How did Mendeleev's predictions contribute to the acceptance of his periodic table?

Mendeleev's predictions of elements like Gallium (Eka-Aluminium) and their properties proved to be correct. Signup and view all the answers

Explain the difference between a dependent and independent variable, using the example of a plant growth experiment.

The independent variable is what you change (e.g., amount of water), and the dependent variable is what you measure (e.g., plant height). Signup and view all the answers

A student notices condensation forming on a cold glass of water. Is this a physical or chemical change? Explain.

This is a physical change because the water is only changing its state from gas to liquid; it's still water. Signup and view all the answers

Describe an observation that would indicate that a chemical change has occurred.

An observation indicating a chemical change is the emission of light or heat from the substance. Signup and view all the answers

A student designs an experiment to test if fertilizer affects tomato yield. What should be the hypothesis?

If fertilizer is added to tomato plants, then the tomato yield will increase, because fertilizer provides additional nutrients for growth. Signup and view all the answers

Provide an example of a malleable metal and explain why this property is useful.

Gold is a malleable metal because it can be formed into thin sheets or wires, which is useful in jewelry making. Signup and view all the answers

Describe how the properties of metalloids make them useful in electronic devices.

Metalloids, like silicon, are semiconductors, meaning they can conduct electricity under certain conditions, which is crucial in transistors and computer chips. Signup and view all the answers

Explain why it was important for Mendeleev to leave gaps in his periodic table.

Leaving gaps allowed for the future placement of elements that were not yet discovered, demonstrating the predictive power of his system. Signup and view all the answers

How did Mendeleev organize the elements in his periodic table, and what properties did he use?

Mendeleev organized elements by atomic mass and grouped them based on similar chemical properties. Signup and view all the answers

Flashcards

Independent Variable

The variable that is changed in an experiment to see its effect on another variable.

Dependent Variable

The variable that is measured in an experiment to see if it is affected by the independent variable.

Controlled Variables

Variables that are kept constant during an experiment to ensure that only the independent variable is affecting the dependent variable.

Physical Change

A change that alters the form or appearance of a substance but does not change it into a new substance; often reversible.